Title of Invention	”Process for Producing Lipids Containing Polyenoic Fatty Acids from Microorganisms".
Abstract	The present invention provides a process for growing eukaryotic microorganisms, which are capable of producing lipids, in particular, lipids containing polyenoic fatty acids. The present invention also provider a process for producing eukaryotic microbial lipids.

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This application comprises a divisional out of the paient Indian Patent Application No. 1N/PCT/2002/00710/DEL. FIELD OF THE INVENTION The present invention is directed to a process for productng lipids containing polyenoic fatty acid from microorganisms and recovering microbial lipids. In particular, the present invention is directed to producing microbial polyunsaturated lipids. BACKGROUND OF THE INVENTION Production of polyenoic fatty acids (fatty acids containing 2 or more unsaturated carbon-carbon bonds) in eukaryotic microorganisms has been generally believed to require the presence of molecular oxygen '(i.e., aerobic conditions). This is because it is believed that the cis double bond formed in the fatty acids of all non-parasitic eukaryotic microorganisms involves a direct oxygen-dependent desaturation reaction (oxidative microbial desaturase systems), Other eukaryotic microbial lipids that are known to require molecular oxygen include fuugal and plant sterols, oxycarotenoids (i.e,, xanthophylls), ubiquinones, and compounds made from any of these lipids (i.e,, secondary metabolites). Certain eukaryotic microbes (such as algae; fungi, including veast; and protists) have been demonstrated to be good producers of polyenoic fatty acids in fermentors. However, very high density cultivation (greater than about 100 g/L microbial biomass, especially at commercial seale) can lead to decreased polyenoic fatty acid contents and hence decreased polyenoic fatty acid productivity. This may be due in part to several factors including the difficulty of rnaintaining high dissolved oxygen levels due to the high oxygen demand developed by the high concentration of microbes in the fermentation broth. Methods to maintain higher dissolved oxygen level include increasing the aeration rate and/or using pure oxygen instead of air for aeration and/or increasing the agitation rate in the fermentor. These solutions generally increase the eost of lipid production and capital eost of fermentation equipment, and can cause additional problems. For example, increased aeration can easily lead to severe foaming problems tn the fermentor at high eeli densities and increased mixing can lead to microbial eeli breaiage due to increased shear forces in the fermentation broth (this causes the lipids to be released in the fermentation broth where they can become oxidized and/or degraded by enzymes). Microbial Cell brsakage is an increased problem in eelis that have undergone nitrogen limitation or - depletion to induce lipid fomation, resultmg in weaker eeli walls. As a result, when lipid-producing eukaryotic microbes are grown at very high eel] concentrarions, Üieir lipids generally contain only very small amounts of poiyenoic fatty acids. For example, the yeasiLipomyces siarkeyi has been grown to a density of 153 g/L with resultmg lipid concentration of 83 g/L in 140 hours -using alcobol as a carbon source. Yet the polyenoic fatty acid content of the yeast at concentration greater than ] 00 g/L averaged only 4.2% of tota] fatty acids (dropping from a high of 11.5% of total fatty acid at a eeli density of 20-30 g/L). Yamaucui et aL, J. Ferment. TechnoL, 1983, 61,275-280. This results in £ polyenoic fatty acid concentration of only about 3.5 g/L and an average polyenoic fatty acid productivity of only about 0.025 g/L/hr. Additionally, the only polyenoic fatty acid reported in the ysast lipids was C18:2. Another yeast, Khoäotorula glutinus, has been demonstrated to have an average lipid productiviry of about 0.49 g/L/hr, biit also a low overall polyenoic fatty acid content in its lipids i (15.8% of total fatty acids, 14.7% C18:2 and 1.2% C18:3) resuiting in a polyenoic fatty acid productivity in fed-batch culture of only about 0.047 g/L/hr and 0.077 g/L/hr in continuous culture, One of the present inventors has previously demonstraied that certain manne microalgae in the order Thraustochytriales can b,e excellent producers of polyenoic fatty acids in fermentors, O especialiy when grown at low salinity levels and especially at very low chloride levels. Others have described Thraustochytrids that exhibit an average polyenoic fatty acid (DHA, C22:6n-3; and DPA, C22:5n-6) productiviry of about 0.158 g/L/hr, when grown to eeli density of 59 g/L in * 120 hours. However, this productivity was only achieved at a salinity of about 50% seawater, a concentration that would cause serious corrosion in conventional stainless steel fermentors. 2 5 Costs of producing microbial lipids containing polyenoic fatty acids, and especially the highly unsaturated fatty acids, such as Cl 8:4n-3s C20:4n-6, C20:5n3, C22:5n-3, C22:5n-6 and C22:6n-3, have reraained high in part due to the limited densities to which the high polyenoic fatty acid containing eukaryotic microbes have been grown and the limited oxygen availability both at these high eel] concentrations and the higher temperatures needed to achieve high 3 O productivity. Tberefore, there is a need fora process for growing microorganisms at high concentration which stiil facilitates increased production of lipids containing polyenoic fatty acids. The present invention provides a process for growing eukaryotic microorganisms that are capable of producmg at Isast about 20% of their biomass as lipids and a method for producing 5 tn e lipids. Preferably the Üpids contain one or more polyenoic fatty acids. The process comprises adding lo a fermentation medium comprising eukaryotic microorganisms a carbon source, preferably a non-alcobol carbor. source. and a limitirig nutrient source. Preferably, the carbon source and the limiting nutrient source .are added at a rate siifficient to increase the biomass density of the fermentation medium to at least about 100 g/L, 10 In one aspect of the present invention, the fermentation condition cornprises a biomass density increasing stage and a lipid production stage, wherein the biomass density increasing stage cornprises adding the carbon source and the limuing nutriem aitrogen SDurce, and the lipid production stage coaiprises adding the carbon source without adding the limiiing nutriem nitrogsn source te create conditions which induce lipid production. 15 In another aspect of the present invention, the amoimt of dissolved oxygen present tn the fermentation medium during the lipid production stage is lower than the amount of dissolved oxygen present in the fermentation medium during the biomass density increasing stage. In yet another aspect of the present invention, microorganisms aje selected from the group eonsisting of algae, fungi (including yeasts), protists. bacteria, and mixtures thereof, 2 O wberein the microorganisms are capable of producing polyenoic fatty acids or other lipids that had been generally believed to require molecular oxygen for their syntaesis. Particularly useful microorganisms of the present invention are eukaryotic microorganisms that are capable of 'producing lipids at a fermentation medium oxygen ievel of about less than 3% of satufation. In stiil another aspect of the present invention, microorganisms are grown in a fed-batch 25 process. Yet stiil another aspect of the present invention provides maintaining an oxygen level of less than abou: 3% of saturation in the fermentation medium during the second half of the fermentation process. Another embodiment of the present invention provides a process for producing 3 O eukaryotic microHal lipids comprising: (a) growing eukaryotic microorganisms in a fermentation medium to increase the biomass density of said fermentaüon medium to at least about 100 g/L; (b) providing fermeritation conditions sufficientto allow said microorganisms to produce said lipids; and (c) recovering said lipids, wherein greater than about 15% of said lipids are polyunsaturated lipids. Another aspect of the present invention provides a lipid recover}' process that comprises: (d) removing water frorn said fermentation medium to provide dry microorganisms; and (e) isoiating said lipids from said dry microorganisms. Preferably, the water removal step comprises contacting the fermentation medium directly on a drum-dryer without prior centrifugation. Another aspect of the present invention provides a lipid recover)'process that comprises: (d) treating the fermentation broth to permeabilize, lyse or'rupture the microbial eelis; and (e) recovering the lipids from the fermentation brcth by gravity separation, and preferably centrifugation, with or without the aid of a water-soluble solvent to aid in breakjng the lipid/water emuision. Preferably. the microbial eelis are treated in step (c) in a fermentor or a similar vessei. ID a further aspect of the present invention, a method for enriching the polyenoic fatty acid content of a mi er o organism is'provided. The method indudes fermenting the microorganisms in a growth medium häving a level of dissolved oxygen of less than 10%. A further aspect of the invention is a heterotrophic process for producing products and microorganisms. The process indudes culturing the microorganisms containing polyketide synthase genes in a growth medium and maintaining the level of dissolved oxygen in the culture at less than about 10 percent. BRIEF DESCRIPTION OF THE DRAWINGS Figure l is a table and a plot of vari õus lipid production parameters of a microorganism versus the amount of dissolved oxygen in a fermentation medium. 6 DETAILED DESCRIPTION OF THE INVENTION The present mvention provides a process for growing microorgamsms, such as, for exarnple, algae, fungi (induding yeast), protists, and bacteria. Preferabiy, microorganisms are selected from the group consisting of algae, protists and mixtures thereof, More preferabiy, 5 microorganisme are algae. Moreover, the process of the present mvention can be used to produce a vanety of lipid compounds, in particular unsaturated lipids. preferabiy polyunsaturated lipids (i.e., lipids contaimng at least 2 unsaturated carbon-carbon bonds, e.g., double bonds), and morepreferabiy highly unsaturated lipids (i.e., lipids containing 4 or more ünsarurated carbon-carbon bonds) such as omegs-3 and/or omega-6 polyunsaturated fatty acids, includtng l O docosahexaenoic acid (i.e., DHA); and other naturally occurring unsaturated, polyunsaturated and highly unsaturated compounds, As used herein. the term "lipid" meludes phospholipids; free fatt}' acids; esters of fatty acids; triacylglycerols; sterols and sterol esters; carotenoids; xanthophylls (e.g., oxycarotenoids); hydrocarbons; isoprenoid-derived compounds and other lipids -known to one of ordinary skill in the art. 15 . More particularly, processes of the present invention are useful in producing eukaryotic microbial poiyenoic fatty acids, carotenoids, fungal sterols, pbytosterols, xanthophylls, ' ubiquinones, and other isoprenoid-derived compounds which had been generally believed to require oxygen forproducing unsaturated carbon-carbon bonds (i.e., aerobic conditions). and secondary metabolites thereof. Specifically. processes of the present invention are useful in 20 growing microorganisrns titat produce poiyenoic fatty acid(s). and for producing microbial poiyenoic fatty acid(s). While processes of the present invention can be used to grow a wide variety of "microorganisms and to obtain polyunsaturated lipid containing compounds produced by the same, for the sake of brevity, convenience and illustration, this detailed description of the 25 invention will discuss processes for growing microorganisms which are capable of producing iipids comprising omega-3 and/or omega-6 polyunsaturated fatty acids, in particular microorganisms thatare capable of producing DHA (or closelyrelated compounds such asDPA, EPA or ARA). Preferred microorganisms inciude microalgae, fungi (including yeast), protists and bacteria. One group of preferred microorganisms is the members of the microbial group 30 called Stramenopiles which indudes microalgae and algae-like microorganisms. The Stramenopiles inciude the following groups of microorganisms: Hamatores, Proteromonads, Opalines, Developayella. Diplophrys, Labrinthulids, Thraustochytrids, Biosecids, Oomycetes, Kypochytridiornyceies, Coramation, Reticulosphaera, Pelagoraonas, Pelagococcus, Ollicola, Aureococcus, Parmales, Diaioms, Xantliophytes, Phaeophytes (brown algae), Eustigmatophytes, RaphidophyteE, Synurids, Axodines (including Rbizochromulinaales, Pedinellales, Dictyochales), Chrysomeridales. Sarcinochrysidales, Hydrurales, Hibberdiales, and Cbromulinales. Other preferred groups of microalgae melude the members of the green algae and dinoflagellates, including members of the genus Ciypthecodium. More particularly, preferred embodiments of the present invention will be discussed with reference to a process for growmg marine microorgamsms, in particular algae, such as Thraustochytrids of tbe order Thraustochytriales, more specifically Thraustochytriales of the genus Thraustochyiriwn and Schizochytrium, including Thraustochytriales which are disclosed rn cornmonly assigned U.S. Patent Nos. 5,340,554 and 5,340,742, both issued to Barclay, all of which are incorporated herein by reference in their entirety. It should be noted that many experts agree that Ulkenia is not a separate genus, but is in fact part of the genus Schizochytrium. As used herein, tbe genus Schizochytrium will indude Ulkenia. Preferred microorganisms are thcse that produce the compounds of interest via polyketide synthase systems. Such 'microorganisms include microorganisms häving an endogenous polyketide synthase systern and microorganisms into which a polyketide synthase system has been genetically engineered. Polykstides are srnicrurally diverse natural products that have a wide range of biological activiries, including antibiotic and pharmacological properties, Bios>iithesis of the carbon chain backbone of polyketides is catalyzedby polyketide synthases. Like the structurally and mechanistically related fatty acid synthases, polyketide synthases catalyze the repeated decarboxylative condensations between acyl thioesters that 'extend the carbon chain two carbons at a time. However, unUke fatty acid synthases, polyketide synthases can generate great structural variability in the end product. In.dividual polyketide syathase systems can do this by usiag starting units other than acetate, by utilizing methyl- or ethyl-malonate as the extending unit and by varying the reductive cycle of ketoreduction. dehydration and enoyl reduction on the beta-keto group formed after each condensation. Of particular interest here is that the carbon-carbon double bonds that are introduced by the dehydration step can be retained in the end product. Further, although fhese double bonds are initially in the trans configuration. they canbe converted to the cis configuration found in DHA (and other polyenoic fatty acids of interest) by enzymatic isomerization. Both the dehydrase and isomerization reactions can occur in the absenae of molecular oxygen. Preferably, in accordance with the present mvention a heterotropliic process is provided for producing products and microorganisms. The process preferably compnses culturing the microorganisms in a growth medium wherein the microorganisms contain a polyketide synthase system. Preferably. the level of dissolved oxygen is maintained at less than about 8 percent, more preferably at iess than aboul 4 percent, more preferably at iess than about 3 percent, and more preferably at less than about l percent. It is to be understood, however, that the invention as a whole is not intended to be so limited, and that one slcilled in the art will recognize that the concept of the present invention will be applicable to other microorganisms producing & variety of other compounds, including other lipid compositions, in accordance with the techniques discussed herein. Assuming a relatively constantproduction rate of lipids by an algae, itis readily apparent that the higher biomass density will lead to a higher total amount of lipids being produced per võlume. Current conventional fermentation processes for growing algae yield a biomass density of from about 50 to about 80 g/L'or less. The present inventors have found that by using processes of the present invention, a significantly higher biomass density than currently known biomass density can be achieved./rreferably, processes of the present invention produc biomass density of at least about 100 g/L, more preferably at least about 130 g/L, stiil rnore preferably at least about 150 g/L, y.et stiil more preferably at least about 170 g/L, .and most preferably greater than 200 g/L. Thus, with such a high biomass density, even if tbe lipids production rate of algae is decreased slightly. the overall iipids production rate per võlume is significantly higher than currently known processes. Processes of the present inventioa for growing microorganisms of the order Thraustochytriales indude adding a source of carbon anc a source of a iimitinc nutricnt to a fermentation mediura comprising the microorganisms at a rate sufficient to increase tbe biomass density of the fermentation medium to tbose described above. As used herein, the term "limiting nutrient source" refers to a source of a nutrient (including the nutrient itselfj essential for the growth of a microorganism in that, when the limiting nutrient is depleted from the growth medium, its absence substantially limits the microorganism from growing or replicating further. However, since the other nutrients are stiil in abundance, the organism can continue to make and accumulate intracellular and/or extracellular products. By choosmg s specific limiting nutrient, one can control the type of products that are accumulated. Therefore, providing a limiting nutrient source at a certain rate allows one to control both the rate of growth of the microorganism and the production or accumulation of desired products (e.g., lipids). This fenrientation process, where one or more substrates (e.g., a carbon source and a limiiingnutrient nitrogen source) are added in increments, is generally 'referred to as a fed-batch fermentation process. It has been found that when the substrate is added to a batch fermentation process the large amount of carbon source present (e.g., about 200 g/L or more per 60 g/L of biomass density) had a detrimental effect on the microorganisms. Without being bound by any theory, it is believed that such a high amount of carbon source causes detrimental effects, including osmotic stress, for microorganisms and inhibits initial productivity of microorganisms. Processes of the present invention avoid this undesired detrirnental effect while providing a sufficient amount of the substrate to achieve the above-described biomass density of the microorganisms. Processes of the present invention for growing microorganisms can include a biomass density increasing stage. In the biomass density rncreasing stage, the primary objective of the fermentation process is to increase the biomass density in the fermentation medium.to obtain the biomass density described above. The rate of carbon source addition is typically maintained ata particular level or range that does not cause a significant detrimental effect on productiviry of microorganisms, or the viability of me microorganisms resulting from insufficient capabilities of the fermentation equipment to remove heat from and transfer gases to and from the liquid brofh An appropriate range of the amount of carbon source needed for a particular microorganism during a fermentation process is well known to one of ordinary slcill in the art. Preferably, a carbon source of the present invention is a non-alcohol carbon source, i.e., a carbon source that does not contain alcohol. As used herein, an "alcohol" refers to a compound häving 4 or less "carbon atorns with one hydroxy group, e.g., methanol, ethanol an'd isopropanolbut for the purpose of this invention does not include hydroxy organic acids such as lactic acid and similar compounds. More preferably, a carbon source of the present invention is a carbohydrate, including, but not limited to, fructose, glucose, sucrose, molasses, and starch. Other suitable simple and complex carbon sources and nitrogen sources are disclosed in the above-referenced patents. Typically, however, a carbohydrate, preferably com syrup, is used as the primary carbon source. Fatry acids, in the form of hydroxy fatty acids, triglycerides, and di- and mono-glycerides can also serve as the carbon source Particularly preferred nitrogen sources are urea, nitrate, nitrite, soy protein, amino acids, protein, com steep liquor, yeast extract, animal byrproducts, inorganic ammonium salt, more preferably ammonium salts of sulfate, hydroxide, and most preferably ammonium hydroxide. Other lirniring nutrient sources include carbon sources (as defmed ahove), phosphate sources, vi tarnin sources (sudi as vitamin Bn sources, pantothenate sources, thiamine sources), and trace metal sources (such as zinc sources, copper sources, cobalt sources, nicke] sources, iron sources, manganese sources; molybdenum sources), and major meta] sources (such as magnesiurn sources, calcium sources,, sodium sources, potassium sources, and silica sources, ete,). Trace meta! sources and major metal sources can indude sulfate and chloride salts of these metals (for example but not limited to MgS(V7H20; MnCl2»4H2O; ZnS(WH20; CoCl2»6H30; Na2Mo(V2H20; CiiS04«5H20; NiSO Processes of the present invention for growing microorganisms can also melude a production stage. Ln this stage. the primary use of the substrate by the microorganisms is not increasing the biomass Qensity but rather using the substrate to produce lipids. It should be appreciated that lipids are also produced by the microorganisms eluring the biomass density increasing stage; however, as stated above, the primary goal.in the biomass density increasing stage is to increase the biomass density. Typically, during the production stage the addition of 'the limiting nutrient substrate is reduced or preferably stopped. It was previously generally believed that the presence of dissolved oxygen in the fermentation medium is crucial in the production of polyunsaturated compounds, incruding omega-3 anoVor omega-6 polyunsaturated fatty acids, by eukaryotic microorganisms. Thus, a relativeiy large amount of dissolved oxygen in the fermentation medium was generally believed to be preferred. Surprisingly and unexpectedly, however, the present inventors have found that the production rate of lipids is increased dramatically when the dissolved oxygen level during the production stage is reduced. Thus, while the dissolved oxygen level inthe fermentation medium during the biomass density increasing stage is preferably at least about 8% of saturation, and preferably at least about 4% of saturation, during the production stage the dissolved oxygen in the fermentation medium is reduced to about 3% of saturation or less, preferably about 1% of saturation or less, and more preferably about 0% of saturation. At tbe beginning of the fermentation the DO can be at or near saturation and as the microbes grow it is allowed to drifl down to these low DO setpoints, In one particular embodiment of the present invention, tbe amount of dissolved oxygen level in the fermentation medium is varied duringthe fermentation process. For example, for a fermentation process with total fermentation time of from about 90 hours to about 100 hours, the dissolved oxyger, level in the fermentation medium is maintained at about 8% durmg the first 24 hours, about 4% from about 24* hour to about 40^ hour, and about C.5% or less from about 40lh hour to the end of the fermentation process. The amount of dissolved oxygen present in the fermentation medium can be controlled by controlling the amount of oxygen in the head-space of the fermentor, or preferably by controlling the speed at which the fermentation medium is agitated (or stirred). For example, a high agitation (or stirrmg) rate restiks in a relatively higher amount of dissolved oxygen in the fermentation medium than a low agitation rate, For example. in a fermentor of about 14,000 gallon capacity the agitation rate is set at from about 50 rpm to about 70 rpm during the first 12 hours, frorn about 55 rpm to about 80 rpm auring about 12* hour to about 18* hour and from about 70 rpm to about 90 rpm from about 18* hour to the end of the fermentation process to achieve the dissolved oxygen level discussed above for a total fermentation process time of from about 90 hours to about 100 hours. A particular range of agitation speeds needed to achieve a particular amount of dissolved oxygen in the fermentation medium can b: readily deterrnined by one of ordinary skill m the art. A preferred temperatuure for processes of the present invention is at least_about^QtCv more preferably at least about 25°C and most preferably at least about 30DC. It should be appreciated tbat cold water can retain a higher amount of dissolved oxygen than warm water. Thus, a higher fermentation medium temperature has the additional benefit of reducing the amount of dissolved oxygen, which is particularly desired as described above. Certain microorganisms may require a certain amount of saline minerals in the fermentation medium. These saline minerals, especially chloride ions, can cause corrosion of the fermentor and other downstream processing equipment. To prevent or reduce these undesired effects due to a relatively large amount of chloride ions present in the fermentation medium, processes of the present invention can also include using non-chloride containing sodium salts, preferably sodium sulfate, in the fermentation mediilm as a source of sodium. More particularly, a significant portion of the sodium requirements of the fermentation is supplied as non-chloride contaming sodium salts. For example, less than about 75% of the sodium in the fermentation medium is supplied as sodium chioride. more preferably less than about 50% and more preferably less than about 25%. The microorganisms of the present invention can be grown at chioride concentratians of less than about 3 g/L. more preferably less than about 500 mg/L, more preferably less than about 250 mg/L and more preferably between about 60 mg/L and about 120 mg/L. Non-chloride containing sodium salts can inciude sõda ash (a mixture of sodium carbonate and sodium cxide), sodium carbonate, sodium bicarbonate, sodium sulfate and mixtures thereof, and preferably inciude sodium sulfate. Sõda ash, sodium carbonate and sodium bicarbonate tend to increase the pH of the fermentation medium, thus requiring control steps to maintain the proper pH of the medium. The concentration of sodium sulfate is effective to meet the salinity requirements of the microorganisms, preferably the sodium concentration is (expressed as g/L of Na) at least about l g/L, more preferably in the range of from about l g/L to about 50 g/L and more preferably in the range of from about 2 g/L to about 25 g/L. Various fermentation parameters for inoculating, growing and recovering microorganisms are discussed in detail in U.S. Patent No. 5,130,242, which is incorporated herein by reference in its entirety. Any currentiy known isolation methods can be usedto isolate microorganisms from the fermentation medium, inciuding centrifugation, filtration, uitrafiltratiDn, decantation. and solvent evaporation. It has be-en found by the present inventors that because of sucb a high biomass density resulting from processes of the present invention, when a centrifuge is used te recover the microorganisms it is preferred to dilute the fermentation "medium by aäding water, which reduces the biomass density, thereby allowing more effective separation of microorganisms from the fermentation medium. The very high biomass densities achieved in the present invention also facilitate "solventless" processes foriecovery of microbial lipids. Preferred processes for lysing the eelis in the fermentor are described in U.S. Provisional Patent Application Serial No. 60/177,125 entitled "SOLVENTLESS EXTRACTION PROCESS" filed January 19, 2000, U.S. Patent Application Serial No. entitled "SOLVENTLESS EXTRACTION PROCESS" filed January 19, 2001, and PCT Patent Application Serial No. entitled "SOLVENTLESS EXTRACTION PROCESS" filed January 19,2001, which are incorporated herein by reference in their entirety. Preferred processes for recovering the lipids once the eelis are permeabilized, broken or lysed in the fermentor (which enables the lipid emuision to be . broken,,and the lipid-rich fraction te be recovered) include tbe deoiling process outlined in WO 96/05278 which is incorporated herein by reference in its entirety. In this process a water soluble compound, e.g., alcohol or acetone, is added to the oil/water emuision to break the emuision and the resiilting mixture is separated by gravity separation, e.g.. centrifugation. This process can also be modified to use other agents (water and/or lipid soluble) to break the emuision. Alternatively, the microorganisms are recovered in a dry form from the fermentation medium by evaporating water frorn the fermentatiorj medium./o?' example, by contacting the fermentation medium directly (i.e., withoul pre-concentration, for example, by centrifugation) with a dryer such as a drum-dryer apparatus, i.e., a direct drum-dryer recovery process. When using the direct drum-dryer recovery process to isolate microorganisms, typically a stearn-heated dmrn-dryer is employed. In addition when using the direc: dnrm-dryer recovery process, the biomass density of the fermentation medium is preferably at least about 130 g/L. mo-re preferably at least about 150 g/L. and most preferabty at least about 180 g/L. This high biomass density is generally desirec for the direct drum-dryer recovery process because at a lowsr biomass density, the fermentation medium comprises a sufncient amount of water to cool the drum significantly, thus resultrng in incoraplete drying of microorganisms. Other methods of drying eelis, including spray drying. are w ell known to one of ordinary skill in the art. Processes of the present invention provide art average lipid production rate of at least about 0.5 g/l/hr, preferably at least about 0.7 g/L/hr, more preferably at least about jQ.9--g/L-/hr, and most preferably at least about 1.0 g/L/hr. Moreover, lipids produced by processes of the "present invention contain polyunsaturated lipids tn the amount greater than about 15%, preferably greater than about 20%, more preferably greater than about 25%, stiil more preferably greater than about 30%, and most preferably greater than about 35%. Lipids can be recovered from either dried microorganisms or from the microorganisms in the ferrnentatjon medium. Generally, at least about 20% of the lipids produced by the microorganisms in the processes of the present invention are omega-3 and/or omega-6 polyunsaturated fatty acids, preferably at least about 30% of the lipids are omega-3 anoVor omega-6 polyunsaturated fatty acids, more preferably at least about 40% of the lipids are ornega-3 and/or omega-6 polyunsaturated fatty acids, and most preferably at least about 50% of the lipids are omega-3 and/or omega-6 polyunsaturated fatty acids. Alternatively, procssses of the present invention provides ar. average omega-3 fatty acid (e.g., DHA) production rate of at leasi about 0.2 g of omega-3 fatty acid (e.g., DHA)/L/hr, preferably at leasl about 0,3 g of omega-3 fatty acid (e.g,, DHA)/L/hr, more preferably at least about 0,4 g of omega-3 fatty acid (e.g., DHA)/L/hr, and roost preferabty ai Isast about 0.5 g of omega-3 fatty acid (e.g.. DHA)/L/hr. Alternatively, processes of the present invention provide an average omega-6 fatty acid (e.g., DPAn-6) production rate of at least about 0.07 g of omega-6 fatty acid (e.g., DPAn-6)/L/hr, preferably at least about 0.1 g of omega-6 fatty acid (e.g., DPAn-6)/L/hr, more preferably at least about ö. 13 g of omega-6 fatty acid (e.g., DPAn-6)/l/hr, and most preferably at least about 0.17 g of omega-6 fatty acid (e.g., DPAn-6)/L/hr. Stil! altematively, at least about 25% of the lipid is DHA (based on total fatty acid methyl ester), preferably at least about 30%, more preferably at least about 35%, and most preferably at least about 40%. Microorganisms, lipids extracted therefrom, the biomass remaining arter lipid extraction or combinations theieof can be used directly as a food ingredient, such as an ingredient in beverages, sauces, darry based foods (such as mille, yogurt. cheese and ice-crearrr) and baked goods; nutritional supplement (in capsule or tablet forms); feed or feed supplernent for any animai whose meat OTproducts are consumsd by humans; food supplement, including baby food and infant formula; and pharrnaceuticals (in direct or adjunct therapy application). The term "animar means any organism belonging to the kingdorn Aiümalia and indudes, witbout liinita ti on, any animai from which poultry meat, seafood, beef, pori; or lämb is derived. Seafood is derived from, without limitation, fish, shrimp and shellfish. The term "products" indudes any product other than rneat derived from such animals. including. without limitation, eggs, mille or other products. When fed to such animals, polyunsaturated lipids can be incorporated into the -flesh, milk, eggs or other products of such animals to increase their content of these lipids. Additional objects, advantages, and novel-features ofthis invention will become appareat to those skilled in the art upon examination of the following examples tbereof, which are not intended to be limiting. EXAMPLES The strain of Schizochytrium used in these examples produces two primary polyenoic acids, DHAn-3 and DPAn-6 in the ratio of generally about 3:1, and srnall amounts of other polyenoic acids, such as EPA and C20:3, under a wide variety of fermentation conditions. Thus, 15 while the following examples only list the amount of DHA, one can readil}' calculate the amount . of DPA(n-6J produced by using the above-disclosed ratio. Example l This exampleillustrates the effect of oxygen content in a fermentation medium on lipid productivity. Fermentationresuks of Schizochytrium ATCCNo. 20888 at various ievels of dissolved oxygen content were measured. The results are shown in Figure l. where RCS is residual concentration of sugar, and DCW is dry-cell weight. Example 2 This example also illustrates the effect of low oxygen content in the fermentation medium on DHA content (% dry weight) of the frnal biomass product. A "scale-down" type experiment was conducted in 250 mL Erlenmeyer flasks to mimic the effect of low oxygen content on the DHA content in Schizochytrium sp. celle cultured in large-scale fermentors. Schizochytrium sp (ATCC 20888) was cultured in 04-4 medium. This culture media consisted of the following on a per liter basis dissolved in deionized water: Na2S04 12.61g; MgS04«7H20 1.2g; KC1 0.25 g; CaCb 0.05 g; monosodium glutamate 7.0 g; glucose l O g; KH2PCU 0.5 g; NaHCO3 0.1 g; yeast extract 0. l g; vitamin mix l .0 mL; PII metals 1.00 rnL. Pü metalnix contains (perliter): 6.0 gNa2EDTA! 0.29 gFeCl3«6E2Os 6.S4 gH3B03! C.86 g MnCl:»4H20, 0.06 g ZnCk 0.026 g CoCl2»6H20, 0.052 g NiSO4»H20, 0.002 CuS04«H20 and 0.005 g Na2Mo04«2H20. Vitamin mix contains (per liter): 100 nig thiamine, 0.5 mgbiotin and 0.5 mg cyanocobalamin. ThepH of the culture media was adjusted to 7.0 and it was then filter sterilized. The idea behind this scale-down experiment was to culture the eelis in shake flasks with different volumes of culture media in the flasks— almost rull flasks (e,g. 200 mL in a 250 mL shake flask) wouldnot mix well on a shake table and therefore as the eelis grew, low dissolved oxygen conditions would be generated. Therefore 4 treätments were established in the experiment, each conducted in duplicate: (3) 250 mL flasks filled with 50 mL culture medium; (2) 25C mL flasks filled with 100 mL culture medium; (3) 250 mL flasks filled with 150 mL culture medium; and (4) 250 mL shake flasks filled with 200 mL culture medium. Each of the eight flasks was inoculated with eelis from a 48 hour oid culture of Schizochytrium cultured in 04-4 medium under the conditions in treatment l ./and at 28DC and 220 rpm on a shaker table. All eight flasks for the experiment were placed on a shaker table (220 rpm) in a mcubator (28°C) and cultured for 48 hours in the dark. At the end of the experiment. dissolved oxygen (DO) levels in each flask were measured with a YS1 dissolved oxygen meter, pH of the culrure medium was also determined, and the dry weight of eelis and their fatty acid content was also measured, The results of the experiment are outlined in Table l. Table 1. Results of scale-down experiment examining effect of low dissolved oxygen concentrations on the lõng chain highly unsaturated fatty acid content (DHA % dry weight) of Schizochytrium sp. (Table Removed) The results indicate that the lipid content (as % FAME) and DHA content (% dry weight) were higher for eelis cultured at low dissolved oxygen levels - the lower the dissolved oxygen level the higher the lipid and DHA content. This is unexpected because oxygen -had been generally believed te be necessary to foim desarurated (double) bonds. It is surprising that so much DHA was formed at low dissolved oxygen level, because DHA is one of the most unsaturated fatty acids. Although the biomass production decreases as the dissolved oxygen level is decreased. the DHA content is increased. Therefore, it is advantageous to have a growth phase with higher dissolved oxygen levels to maximize the formation of biomass and then lower the dissolved oxygen level to maximize lõng chain fatty acid production. Example 3 This example illustrates the reproducibility of processes of the present invention. Microorganisms were produced using fermentors with a nominal working võlume of 1,200 gallons. The resulting fermentation broth was concentrated and microorganisms were dried using a drum-dryer. Lipids from aliquots of the resulting microorganisrns were extracted and punfied to produce a refmed, bleached, and deodorized oil. Approximately 3,000 ppm of d-!-a-tocopheryl acetate was added fornutritiona] suppi emen tati on purposes prior to analysis of the lipid. Nine fermentaüons of Schizochylrium ATCC No. 20888 were run and the resultE are sLown in Table 2. The dissolved oxygen level was about 8% dunng the first 24 hours and about 4% thereafter. Table 2. Feö-batch fennentation results for the production of DHA from Schizochytrium sp. (Table Removed) 1. actual yield of biomass density. 2. DHA content as % cell dry weight. 3. total fatty acid content as % cell dry weight (measured as methyl esters). 4. (grams of DHA)/L/Hr. 5. average. 6. standard deviation. 7. coefficients of variability. Coefficients of variability values below 5% indicate a process which has excellent reproducibility, values between 5% and 10% indicate a process which has good reproducibility and values between 10% and 20% indicate a process which has reasonable reproducibility. Com syrup was fed until the võlume in.the fermentor reached about 1,200 gallons, at which tiine the com syrup addition was stopped. The fermentation process was stopped once the residual sugar concentration fell below 5 g/L. The typical age, from inoculation to final, was about 100 hours. The fermentation broth, i.e., fermentation medium, was diluted with water usina approximatel}' a 2: l ratio to r-educe the ash content of the final product and help improve phase separation during the centrifugation step. The concentrated eeli paste was heated to 160° F fabout 71° C) and dried on a Blaw Knox double-drum dryer (42"x36"). Preferably, however. microorgamsms are dried directly on E drum-dryer without prior centrifugation. The analysis result of lipids extracted from aliquots of each entries in Table 2 is summarized ir. Table 3. Table 3. Analysis of the microbial biomass produced in the fed-batch fermentations outlined ui Table. 2. (Table Removed) see Table 2. see discussion above. standard deviation. coefficients of variability. CoefEcients of variability values below 5% indicates a process which has excellent reproducibility, values between 5% and 10% indicates a process which has good reproducibility anfl values between 10% and 20% indicates a process which has reasonable reproducibility. Unless otherwise stated, the fermentation-medium used tnroughout the Examples section indudes the following ingredients, where the first number indicates nominal target concentration and the number in parenthesis indicates acceptable range: sodium sulfate 12 g/L (11-13); KCI 0.5 g/L (0.45-0.55); MgS(V7H20 2 g/L (l .8-2.2); Hodag K-60 antifoam 0.35 g/L (0.3-0.4); K2S04 0.65 g/L (0.60-0.70); KH2PO^ l g/L (0.9-1.1); (NlLOaSO l g/L (0.95-1.1); CaCl2»2H20 0.17 g/L (0.15-0.19); 95 DE com syrup (solids basis) 4.5 g/L (2-10); MnCl2«4H20 3 mg/L (2.7-3.3); ZnSO7H20 3 mg/L (2.7-3.3); CoCI2»6H20 0.04 mg/L (0.035-0.045); Na2Mo04»2H20 0.04 mg/L (0-0.045): CuS04-5H20 2 mg/L (l .8-2,2); NiSO4-6H20 2 mg/L (l .8-2.2); FeSO^»7H2O 10 mg/L (9-11); thiamine 9.5 mg/L (4-15); vitamin B,2 '0.15 mg/L (0.05-0.25) and Calciuiru^Pantothenate 3.2 mg/L (1.3-5.1). 'In addition, 28°/cTNH4OH solution is used as the nitrogen source, The ash content of the dried microorganisms is about 6%.b)' weight. Example 4 This example iilustrates the effect o: reduced dissolved oxygen .level in the fermentation medium on the productivity of rnicroorganisms at the 14,000-gallon seale. Using the procedure described in Example 3, a 14,000-gallon norrunal võlume fermentation was conducted using a wild-type strain Schizochytrium, wkich car. be oblained using isolation processes disclosed in the above-mentioned U.S. Patent Nos. 5,340,594 and 5,340,742. The dissolved oxygen level in the fermentation medium was about 8% during the first 24 hours, about 4% from the 24* hour to the 40th hour and about 0.5% from the 40^ hour to . the end of fermentation process. Results of this lower dissolved oxygen level in fermentation medium processes are shown in Table 4. Table4. Results of 14,000-gallon seale fed-batch fermentations of Schizochytrium atreduced dissolved oxygen concentraüons. (Table Removed)20 (Table Removed)Example 5 This example illustrates the effect of reduced dissolved oxygen level in the fermentation medium on the productivity of microorganisms OD a 41,000-gallon seale. The same procedures as Example 4 were employed except that the fermentation was conducted in a 41,000-galion fermentor. Culture media volumes were increased to rnaintain target compound concentrations at this seale. Results are sbown in Table 5. Table 5. 41,000-gallon seale fermentation of Schiiochylrium (Table Removed)Example 6 This example illustrates the affect of extra nitrogen on the fermentation process of the present inventioa Four sets of 250-L seale fed-batch experiments were conducted using a procedure sknilar to Exarnpie 4. Two control experiments and two experiments containing extra ammonia (l. 15x and l.2Sx the normal amount) were conducted. Results are shown in Table 6. Table 6. Affects of extra ammonia on fermentation of Schizochytrium. (Table Removed) (Table Removed)In eneral, extra nitrogen has a negative effect on fermentation performance, as significant reductions were observed in the DHA productivity for the two batches where extra arnmonia was added. As shown on Table 6, the control batches resulted in final DHA levels of 18.4% and ^22.1% of total cellular dry weight versusthe 9.2% (1.15x ammonia) and 12.6% (l .25x ammonia) for extra nitrogen supplemented batches. Example 7 This example shows a kinetic profile of a fermer.tationprocess of the present invention. A 1000-gallon seale fed-batch experiment was conducted using a procedure similar to Example 4. Kinetic profile of the ferrnentation process is shown in Table 7.Table 7. Schizodtytrium. Kinetic Profile for a 1,000-gaIlon scaie Fed-Batcb fermentation of (Table Removed) **Two separate samples were analyzed ai 48 hrs. **This is for a washed dry-cell weights (DCW) sample. Other reported values are for unwashed samples. Example 8 This example illustrates affect of the amount of carbon source on productiviry._ Three.different fermentation processes using the process of Example 4 were condiicted using various amounts of carbon source. Results are shown on Table 8. Table 8. Fermentation results for various amounts of carbon source on fermentation of Schizochytrium. (Table Removed)Example 9 This example illustrates the effect of nutrient limitation on carbon conversion efficiency to biomass, lipid and most specifically DHA. A continuous culture experiment to investigate the effect of nutrient limitation was performed by culturing Schizochytrium ATCC No. 20888 in a 2-liter võlume Applikon fermentor in basal growth (ICM-2) medium consisting of the following compounds (nominal concentration): Gronp I ingredients: Na2SO A continuous operation mode was then established by simultaneously pumping sterile ICM-2 feedmedium into the fermentor .and removing the broth containing Schizocinnrium eelis at a flowrate sufficient to maintain a dilution rate of O.Oõhr"1, until a steady state is reached. To investigate the effect of nutrient limitation, the compound containing the specified required nutrient is lowered in the ICM-2 feed medium such that this nutrient is depleted in the outlet eeli-containing broth, so that growth of the eelis is limited by absence of the particular required nutrient. Once steady state operation was established for each condition, final broth dry biomass, residual glucose, and limiting nutrient concentrations, lipid content of the eeli and DHA content of the eelis were measured. The conversion efficiency of glucose to biomass was calculated by dividing the total glucose consumed by the total dried biomass formed. and expressed on a. percentage basis. The effects of limiting growth by each individual nutrient were studied by repeating this experiment for each individual nutrient listed in the following table. Pinal results are summarized in the following table: Table 9, Effect of nutrient limitation on the biomass yield, conversion efficiency (glucose -> biomass], lipid content and DHA content of Schizochytrium sp. (Table Removed) 1. Concentration of dry biomass (grams/liter) 2. yield coefficient (% biomass produced/glucose consumed) 3. residual glucose concentration in broth (grams/liter) 4. lipid content of dry biomass (g lipid (as FAME)/g dry biomass) 5. DHA content of dry biomass (g DHA/g dry biomass) It is clear from the table tbat nitrogen limitation resulted in the higliest accunrulation of DHA in the eelis, followed by pnosphate, sodium, nickel, manganese, glucose(carbon), zinc and iron. This information can be employed commercially by feeding one ormore oftnese nutrients to a batch fermentation at a rate sufficienl to limit eeli growth. In the most preferred case, nitrogen is fed in a limiting manner to the batch fermentation to maximize the DHA content of the eelis. Other nutrients (or mixtures thereof) can be fed in a limiting manner to maximize production of biomass or other valuable products.. Other biologically required elements or nutrients that were not evaluated. such as sulfur, could also be employed as limiting numents in this fermentation control strategy. The present invention, in varioiis embodiments. meludes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, inclutüng various embodiments, subcombinations, and subsets thereof. Those of skill in the art wil] understandbow to make and use the present invention after understanding the present disc-losure. The present invention, in various embodiments, indudes providmg devices and processes in the absence of items not depicted andVor described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for irnproving performance. achieving ease and\or reducing eost of implementation. The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to tbe forrr. or forms disclosed herein. Although the description of the invention has included description of one or more embodiments aud certain variations and modifications, other variations andmodifi-cations are within the scope of the'invention, e.g.,.a.s may be withm the skill andlcnowledge of those in the art, after understandiug'the present disclosure. It is intended to obtain rights which indude alternative embodiments to the exteni permitted. including altemate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and wthout intending to publicly dedicate any patentable subject märter. We claim: l. A process for producing lipids containing polyenoic fatty acids from microorganisms of the order Thraustochytriaies capable of producing at least about 15% of the total lipids produced by said microorganisms as polyunsaturated lipids comprising conducting a fermentation of the microorganisms in a medium comprising anon-alcohol carbon source, and a limiting. nutrient source: wherein non-alcohol carbon source and iimiting nutrient source are added to the medium to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry eeli weight basis; and wherein the fermentation of the medium häving a biomass density of at least about 100 g/L on a dry eeli weight basis produces lipids containing polyenoic fatty acids. 2. The process of claim l, wherein the process is a fed-batch process. 3. The process of claim l, wherein the process is not a fed-batch process. 4. The process of ciaim l, wherein when biomass density of the fermentation medium is at least about 100 g/L on a dry eeli weight basis, carbon source is added with no or little additional limiting nutrient source to induce nutrient iimiting conditions which induces lipid production. 5. The process of claim l, wherein when the fermentation of the medium produces lipids containing polyenoic fatty acids, the biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis. 6. The process of claim l, wherein the process is conducted for at least 90 hours, wherein the dissolved oxygen level in the fermentation medium is maintained at about 8% during the first 24 hours, about 4% from the 24* hour to the 40th hour, and about 0.5% or less from the 40th hour to the end o f the process, 7. The process of Claim l, wherein the dissolved oxygen level in the fermentation medium is maintained at about 0.5% or less after 40 hours of the process until the end of the process. 8. The process of Claim ], wherein the non-alcohol carbon source comprises acarbohydrate. 9. The process of Claim l, wherein the limiting nutrient source comprises a nutrient source selected from the group consisting of nitrogen sources, carbon sources, phosphate sources, vitamin sources, trace metal sources, major metal sources, silica sources and mixtures thereof. 10. The process of Claim l, wherein the limiting nutrient source comprises a nutrient source selected from the group consisting of a trace metal source and a major metal source selected from the group consisting of sulfate and chloride salts of these metals and mixtures thereof. 11. The process of Claim l, wherein the limiting nutrient source comprises a nitrogen source. 12. The process of Claim l, wherein the limiting nutrient source comprises an inorganic ammonium salt. 13. The process of Claim l, wherein the limiting nutrient source comprises ammonium hydroxide. 14. The process of Claim l, wherein pH of the fermentation medium is controlled by a limiting nutrient source. 15. The process of Claim l, wherein the fermentation medium is at a temperature of at least about 20 C. 16. The process of Claim l, wherein the process produces at least about 15% of the total lipids produced by the microorganisms as polyunsaturated lipids. 17. The process of Claim l, wherein the process produces at least about 15% of the total lipids produced by the microorganisms as docosahexaenoic acid. 18. The process of Claim l, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr. 19. The process of Claim l, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr and wherein at least about 15% of the lipids are polyunsaturated lipids, 20. The process of Claim l, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr and wherein the total amount of omega-3 and omega-6 fatty acids is at least about 20% of the lipids. 21. The process of Claim l, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr and wherein at least about 25% of the lipids is docosahexaenoic acid. 22. The process of Claim l, wherein the microorganisms are capable of producing polyenoic fatty acids or other lipids which can be produced under aerobic conditions. 23. The process of Claim 22, wherein the microorganisms produce polyenoic fatty acids or other lipids produced under aerobic conditions. 24. The process of Claim l, wherein the microorganisms are capable of producing polyenoic fatty acids or other lipids which can be produced under aerobic conditions, and wherein the microorganisms are grown in a fed-batch process. 25. The process of Claim 24, wherein the microorganisms produce polyenoic fatty acids or other lipids produced under aerobic conditions. 26. The process of Claim l, wherein the microorganisms are capable of producing polyenoic fatty acids or other lipids which can be produced under aerobic conditions and wherein the microorganisms are grown in a fed-batch process. 27. The process of Claim l, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof. 28. The process of Claim l, wherein the dissolved oxygen in the fermentation medium is controlled. 29. The process of Claim 28, wherein the dissolved oxygen in the fermentation medium is controlled by step selected from the group consisting of controlling the amount of oxygen in the head-space of the fermentor and controlling the speed at which the fermentation medium is agitated. 30. The process of Claim l, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 31. The process of Claim l, further comprising: a. retnoving water from the fermentation medium to provide dry microorganisms; and b. isolating the lipids from the dry microorganisms, wherein at least about 15% of the microbial lipids are polyunsaturated lipids. 32. The process of Claim 30, wherein at least about 15% of the microbial lipids are docosahexaenoic acid. 33. The process of Claim l, further comprising: a. treating the fermentation medium to permeabilize, lyse or rupture the microbial eelis; and b. recovering the lipids from the fermentation medium by gravity separation, with or without the aid of an agent to aid in breaking the lipid/water emulsion wherein at least about 15% of the microbial lipids are polyunsaturated Hpids. 34. The process of Claim 32, wherein at least about 15% of the microbial lipids are docosahexaenoic acid. 35. The process of Claim l, further comprising: a. evaporating water from the fermentation medium without prior centrifugation to provide dry microorganisms; and b. isolating the lipids from the dry microorganisms wherein at least about 15% of the microbial lipids are polyunsaturated lipids. 36. The process of Claim 34, wherein at least about 15% of the microbial lipids are docosahexaenoic acid. 37. The process of Claim l, wherein a level of dissolved oxygen is less than about 5 % of saturation in the fermentation medium. 38. The process of Claim l, wherein a level of dissolved oxygen is less than about l % of saturation in the fermentation medium. 39. A process for producing lipids containing polyenoic fatty acids from microorganisms of the order Thraustochytriales capable of producing at least about 20% of their biomass as lipids comprising conducting a fermentation of the microorganisms in a medium comprising a source of carbon: wherein the source of carbon is added to the fermentation medium in a fed-batch process to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry eeli weight basis; and wherein the fermentation of the medium häving a biomass density of at least about 100 g/L on a dry eeli weight basis produces lipids containing polyenoic fatty acids. 40. The process of claim 39, wherein when the fermentation of the medium produces lipids containing polyenoic fatty acids, the biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis. 41. The process of Claim 39, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr. 42. The process of Claim 39, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytnum, and mixtures thereof. 43. The process of Claim 39, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 44. A process for producing lipids containing polyenoic fatty acids from microorganisms of the order Thraustochytriales capable of producing at least about 20% of their biomass as lipids comprising conducting a fermentation of the microorganisms in a medium comprising a non- alcohol carbon source, and a limiting nutrient source: wherein non-alcohol carbon source and limiting nutrient source are added to the medium to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry eeli weight basis; and wherein the fermentation of the medium häving a biomass density of at least about 100 g/L on a dry eeli weight basis produces lipids containing polyenoic fatty acids. 45. The process of claim 44, wherein the process is a fed-batch process. 46. The process of claim 44, wherein when the fermentation of the medium produces lipids containing polyenoic fatty acids, Jhe biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis. 47. The process of Claim 44, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr. 48. The process of Claim 44, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof. 49. The process of Claim 44, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 50. A process for producing lipids containing polyenoic fatty acids from microorganisms of the order Thraustochytriales capable of producing at least about 15% of the total lipids produced by the microorganisms as polyunsaturated lipids comprising conducting a fermentation of the microorganisms in a medium comprising a source of carbon: wherein the source of carbon is added to the fermentation medium in a fed-batch process to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry eeli weight basis; and wherein the fermentation of the medium häving a biomass density of at least about 100 g/L on a dry eeli weight basis produces lipids containing polyenoic fatty acids. 51. The process of claim 50, wherein when the fermentation of the medium produces lipids containing polyenoic fatty acids, the biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis. 52. The process of Claim 50, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr. 53. The process of Claim 50, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof. 54. The process of Claim 50, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 55. A process for growing microorganisms of the order Thraustochytriales capable of producing at least about 20% of their biomass as lipids comprising conducting a fermentation of the microorganisms in a medium comprising a carbon source, and a limiting nutrient source: wherein carbon source and limiting nutrient source are added to the medium to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry eeli weight basis; wherein the fermentation of the medium häving a biomass density of at least about 100 g/L on a dry eeli weight basis produces lipids containing polyenoic fatty acids; wherein the process produces at least an average rate of about 0.5 g/L/hr of lipids; and wherein at least about 15% of the total lipids produced by the microorganisms is polyunsaturated lipids. 56. The process of claim 55, wherein the process is a fed-batch process. 57. The process of claim 55, wherein when the fermentation of the medium produces lipids containing polyenoic fatty acids, the biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis. 58. The process of Claim 55, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof. 59. The process of Claim 55, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 60. A process for growing microorganisms of the order Thraustochytriales comprising conducting a fermentation of the microorganisms in a medium comprising a carbon source, and a Hmiting nutrient source: wherein the carbon source and limiting nutrient source are added to the medium to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry eeli weight basis; wherein the fermentation of the medium häving a biomass density of at least about 100 g/L on a dry eeli weight basis produces lipids containing polyenoic fatty acids; and wherein the microorganisms are capable of producing at least about 20% of their biomass as lipids comprising some polyenoic fatty acids. 61. The process of claim 60, wherein the process is a fed-batcb process. 62. The process of claim 60, wherein when the fermentation of the medium produces lipids containing polyenoic fatty acids, the biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis. 63. The process of Claim 60, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr. 64. The process of Claim 60, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof. 65. The process of Claim 60, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 66. A process for producing microbial lipids comprising: growing microorganisms of the order Thraustochytriales in a fermentation medium to increase the biomass density of the fermentation medium; allowing the microorganisms to produce the lipids when the biomass density of the fermentation medium to at least about 100 g/L on a dry cell weight basis; and recovering the lipids, wherein greater than about 15% of the lipids are polyunsaturated lipids. 67. The process of claim 66, wherein the process is a fed-batch process. 68. The process of claim 66, wherein during the step of allowing the microorganisms to produce the lipids, the biomass density of the fermentation medium is at least about 150 g/L on a dry cell weight basis. 69. The process of Claim 66, wherein the process produces lipids at an average rate of at least about 0.5 g/L/hr. 70. The process of Claim 66, wherein the microorganisms are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof. 71. The process of Claim 66, wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid. 72. A process for producing microbial lipids comprising conducting a fermentation of microorganisms in a medium comprising a carbon source, and a limiting nutrient source: adding carbon source and Hmiting nutrient source to a fermentation medium to increase the biomass density of the fermentation medium to at least about 100 g/L on a dry cell weight basis; producing lipids when ih e fermentation medium has a biomass density of at least about 100 g/L on a dry eeli weight; and recovering the microbial lipids; wherein at least about 15% of the microbial lipids are polyunsarurated lipids, T 73. The process of claim 72, wherein the process is a fed-batch process. 74. The process of claim 72. wherein during the step of producing lipids, the biomass density of the fermentation medium is at least about 150 g/L on a dry eeli weight basis, 75. The process of Claim 72. wherein the proeess produces lipids at an average rate of at least about 0.5 g/L/hr. 76. The process of Claim 72. wherein the microorganisms are selected from the group consisting of Thraustochytrium. Schizochytrium. and mixtures thereof. 77. The process of Claim 72. wherein the process produces on average at least about 0.2 g/L/hr of docosahexaenoic acid.

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