FIELD OF INVENTION

[0001] The present invention relates to a method of reducing the self-heating propensity of a microbial biomass which contains significant amount of polyunsaturated fatty acids.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of the filing date of United States Provisional

Patent Application No. 62/952,175, filed December 20, 2019, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0003] Polyunsaturated fatty acids (PUFAs) containing lipids are of high interest in the feed, food and pharmaceutical industry. Fatty acids are classified based on the length and saturation characteristics of the carbon chain. Fatty acids are termed short chain, medium chain, or long chain fatty acids based on the number of carbons present in the chain. Fatty acids are termed saturated fatty acids when no double bonds are present between the carbon atoms. Fatty acids are termed unsaturated fatty acids when double bonds are present. Unsaturated long chain fatty acids are monounsaturated when only one double bond is present. Unsaturated long chain fatty acids are polyunsaturated when more than one double bond is present.

[0004] PUFAs can be produced by microorganisms in a fermentation process. The biomass of the PUFA-containing microorganism is collected before being processed to extract the PUFA oil contained within. The biomass of the PUFA-containing microorganism can also be used directly as a product, particularly in the feed industry.

[0005] It has been found that PUFA-containing compositions are susceptible to self heating. For example, during storage or transportation, the temperature of the biomass in the container or package can increase spontaneously, some will ultimately result in unexpected explosions and fires.

[0006] Some attempts have been made in the past to reduce the self-heating propensity of biomass. For example, WO 2011/054800 describes a process in which the moisture of biomass is controlled during the drying step in order to reduce the self-heating propensity of the biomass. W02018/005856 describes the use of antioxidants to enhance the oxidative stability of algal biomass.

[0007] However, self-heating remains as a challenging problem in transportation and storage of biomass which contains high amount of PUFAs. Thus, there is a need to identify new methods which can effectively reduce self-heating in biomass.

BRIEF SUMMARY OF THE INVENTION

[0008] In an embodiment, a composition is provided comprising more than 30 wt% vegetable oil and at least 50 wt% microbial cells, wherein said microbial cells comprise one or more type of polyunsaturated fatty acid (PUFA) having at least 20 carbon atoms and at least three double bonds, wherein the microbial cells has at least 20 wt% PUFAs, and wherein the composition’s self-heating onset temperature is at least 250 °C. In a particular embodiment, the microbial cells comprise at least 30 wt% PUFAs. In a particular embodiment, the microbial cells comprise at least 40 wt% PUFAs. In a particular embodiment, the microbial cells comprise at least 50 wt% PUFAs. In a particular embodiment, the PUFA is an w-3 or an w-6 PUFA. In a particular embodiment, the microbial cells are ruptured. In a particular embodiment, composition comprises more than 40 wt% vegetable oil. In a particular embodiment, the composition comprises more than 30 wt% vegetable oil and remainder wt% microbial cells. In a particular embodiment, the vegetable oil is canola oil. In a particular embodiment, the microbial cells are of the genus Mortierella , Schizochytrium , Thraustochytrium , Aurantiochytrium , or Crypthecodinium. In a particular embodiment, the onset of composition’s self-heating is measured by heating the composition packed in a 6cm ³ sample tube in a Grewe-Oven with a heating rate of lK/min and an airflow of 2L/min. In a particular embodiment, the microbial cells are in the form of a biomass. In a particular embodiment, the microbial cells are a single strain of microorganism. In a particular embodiment, the composition’s self-heating onset temperature is at least 270 °C. In a particular embodiment, the composition’s self-heating onset temperature is at least 290 °C. In a particular embodiment, the composition’s self-heating onset temperature is at least 300 °C.

[0009] In an embodiment, a method is provided for increasing the self-heating onset temperature of a composition to at least 250 °C, wherein the composition comprises more than 30 wt% vegetable oil and at least 50 wt% microbial cells, wherein said microbial cells comprise one or more polyunsaturated fatty acid (PUFA) having at least 20 carbon atoms and at least three double bonds, wherein the microbial cells has at least 20 wt% PUFAs, and therein the method comprises mixing the microbial cells with the vegetable oil and rupturing the microbial cells. In a particular embodiment, the microbial cells comprise at least 30 wt% PUFAs. In a particular embodiment, the microbial cells comprise at least 40 wt% PUFAs. In a particular embodiment, the microbial cells comprise at least 50 wt% PUFAs. In a particular embodiment, the PUFA is an w-3 or an w-6 PUFA. In a particular embodiment, the microbial cells are ruptured. In a particular embodiment, the composition comprises more than 40 wt% vegetable oil. In a particular embodiment, the composition comprises more than 30 wt% vegetable oil and remainder wt% microbial cells. In a particular embodiment, the vegetable oil is canola oil. In a particular embodiment, the microbial cells are of the genus Mortierella, Schizochytrium , Thraustochytrium , Aurantiochytrium , or Crypthecodinium. In a particular embodiment, the onset of composition’s self-heating is measured by heating the composition packed in a 6cm ³ sample tube in a Grewe- Oven with a heating rate of lK/min and an airflow of 2L/min. In a particular embodiment, the microbial cells are in the form of a biomass. In a particular embodiment, the microbial cells are a single strain of microorganism. In a particular embodiment, the composition’s self-heating onset temperature is at least 270 °C. In a particular embodiment, the composition’s self-heating onset temperature is at least 290 °C. In a particular embodiment, the composition’s self-heating onset temperature is at least 300 °C.

BRIEF SUMMARY OF DRAWINGS

[0010] The patent or application file contains at least one drawing executed in color.

Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0011] Fig. 1 shows the flowability of four compositions which are made of a mixture of ruptured microbial cell biomass and vegetable oil at different ratios, ranging from 30%:70% to 70%:30% (biomass: vegetable oil). (A): Biomass : Canola oil = 30%:70%; (B): Biomass : Canola oil = 40%:60%; (C): Biomass : Canola oil = 50%:50%; (D): Biomass : Canola oil = 70%:30%. [0012] Fig. 2 shows the temperature change curves which were measured over time both inside the 6 cm ² testing vessel and in the Grewe-oven and the onset temperature of the first self heating event. The testing vessel contains 100% microbial cell biomass. [0013] Fig. 3 shows the temperature change curves which were measured over time both inside the 6 cm ² testing vessel and in the Grewe-oven and the onset temperature of the first self- heating event. The testing vessel contains 70% microbial cell biomass and 30% vegetable oil. [0014] Fig. 4 shows the temperature change curves which were measured over time both inside the 6 cm ² testing vessel and in the Grewe-oven and the onset temperature of the first self- heating event. The testing vessel contains 60% microbial cell biomass and 40% vegetable oil. [0015] Fig. 5 shows the temperature change curves which were measured over time both inside the 6 cm ² testing vessel and in the Grewe-oven and the onset temperature of the first self- heating event. The testing vessel contains 50% microbial cell biomass and 50% vegetable oil. [0016] Fig. 6 shows the temperature change curves which were measured over time both inside the 6 cm ² testing vessel and in the Grewe-oven and the onset temperature of the first self- heating event. The testing vessel contains 30% microbial cell biomass and 70% vegetable oil. [0017] Fig. 7 shows the temperature change curves which were measured over time both inside the 6 cm ² testing vessel and in the Grewe-oven and the onset temperature of the first self- heating event. The testing vessel contains 100% vegetable oil.

[0018] Fig. 8 shows the changes of the onset temperature of the first self-heating event in connection with the changes of the wt% of microbial cell biomass.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Dried PUFA-containing oleaginous biomass is known to undergo oxidization thus is susceptible to spontaneous self-heating. Such self-heating problem is especially significant in microbial cells which contains long chain polyunsaturated fatty acids (LC-PUFA). The higher PUFA content there is in a composition, the more likely that the composition is susceptible to spontaneous self-heating. In particular, PUFAs with 20 or more carbon atoms have higher susceptibility to self-heating. It is also known that the susceptibility of a biomass increases with higher number of double bonds of the PUFAs. In particular, PUFAs with 3 or more double bonds have higher susceptibility to self-heating.

[0020] One indicator of the self-heating propensity of a composition is the onset temperature for a spontaneous temperature increase to occur when the composition is heated up at a linear rate. A sudden increase (“spike”) of temperature indicates that the composition heats up spontaneously by itself instead of by the external heating source. The higher of this onset temperature is for a composition, the less susceptible that the composition is to self-heating. Conversely, the lower of this onset temperature is for a composition, the more susceptible that the composition is to self-heating. Any process which can significantly increase the onset temperature of a composition and thus cause self-heating to occur at a higher temperature is considered an effective method for reducing the risk of self-heating,

[0021] It is surprisingly found in this invention that the onset temperature for self-heating of a PUFA-containing oleaginous biomass can be rendered significantly higher by rupturing the biomass and mixing the resulting cell debris/ PUFA oil combination with at least 40 wt% vegetable oil. The resulting composition has a self-heating onset temperature which is about 140 °C higher than onset temperature of 150 °C that is normally observed in the same biomass before the treatment.

[0022] By employing the above methods, a biomass composition with reduced self-heating propensity was produced.

[0023] The self-heating onset temperature is determined by a test described in VDI-

Guideline, available from Beuth Verlag GmbH, Berlin, Germany, published in May 1992, with the following adaptations and specification: a glass vessel with a 6 cm ² volume is used. The sample size is 100% of the volume of the vessel. The vessel is closed with a rubber stopper, tightened to prevent air intake. A thermocouple is inserted in the vessel through a hole in the center of the stopper. The vessel containing the sample, which has an initial temperature of 20 °C, is placed in a Grewe oven. A thermocouple is placed in the oven for monitoring the temperature increase within the oven. The oven is heated in a way to maintain a heating rate of lK/min with an airflow rate of 2L/min. The heating is stopped when the oven temperature reaches 450 °C.

[0024] In one embodiment, the invention is directed to a composition comprising more than 30 wt% vegetable oil and at least 50 wt% microbial cells, wherein said microbial cells comprise one or more type of polyunsaturated fatty acid (PUFA) having at least 20 carbon atoms and at least three double bonds, wherein the microbial cells has at least 20 wt% PUFAs, and wherein the composition’s self-heating onset temperature is at least 250 °C.

[0025] In some embodiments, the microbial cells according to the invention have an oil content and PUFA as described below. [0026] The microbial cells of the invention have self-heating propensity before treatment because it contains a reasonable level of polyunsaturated fatty acids. In one embodiment, the microbial cells comprise at least 20 wt.%, for instance at least 25 wt.%, for instance at least 30 wt.%, for instance at least 35 wt.%, for instance at least 40 wt.%, for instance at least 45 wt.%, for instance at least 50 wt.%, for instance at least 55 wt.%, for instance at least 60 wt.%, for instance at least 65 wt.%, for instance at least 70 wt.%, for instance at least 75 wt.%, for instance at least 80 wt.%, for instance at least 90 wt.%, for instance at least 95 wt.% PUFA. In another embodiment, the microbial cells comprise between 20-50 wt.%, 20-30 wt.%, 20-40 wt.%, 20-50 wt.%, 20-60 wt.%, between 30-70 wt.%, between 40-60 wt.%, or between 45-55 wt.% PUFAs. In one embodiment, the weight of the microbial cells is referred to as the dry cell weight of a biomass. Such biomass can be algal cells or any other PUFA-containing microbial cells.

[0027] In an embodiment of the invention, the composition comprises PUFA, specially

LC-PUFA. In one embodiment, the composition comprises a biomass. In another embodiment, the composition comprises a dried biomass. In another embodiment, the composition comprises the dried biomass of microbial cells. In another embodiment, the composition comprises the dried biomass of algal cells. In one embodiment, the microbial cells or algal cells are ruptured. The cells are considered ruptured when the oil contained in the cells, such as PUFA oil, is released from the cells.

[0028] In an embodiment of the invention, the composition comprises at least 35 wt% vegetable oil and at least 50 wt% microbial cells. In an embodiment of the invention, the composition comprises at least 40 wt% vegetable oil and at least 50 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 90 wt% vegetable oil and between 10 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 90 wt% vegetable oil and between 10 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 80 wt% vegetable oil and between 20 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 70 wt% vegetable oil and between 30 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 60 wt% vegetable oil and between 40 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 50 wt% vegetable oil and between 50 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 80 wt% vegetable oil and between 20 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 70 wt% vegetable oil and between 30 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 60 wt% vegetable oil and between 40 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 50 wt% vegetable oil and between 50 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between at least 30 wt% vegetable oil and the remainder wt% microbial cells. In another embodiment, the composition comprises between at least 35 wt% vegetable oil and the remainder wt% microbial cells. In another embodiment, the composition comprises between at least 40 wt% vegetable oil and the remainder wt% microbial cells. In some specific embodiments, the composition comprises between 40 wt% vegetable oil and the 60 wt% microbial cells, or comprises between 35 wt% vegetable oil and the 65 wt% microbial cells, or comprises between 45 wt% vegetable oil and the 55 wt% microbial cells, or comprises between 45 wt% vegetable oil and the 55 wt% microbial cells, or comprises between 50 wt% vegetable oil and the 50 wt% microbial cells, or comprises between 60 wt% vegetable oil and the 40 wt% microbial cells, or comprises between 70 wt% vegetable oil and the 30 wt% microbial cells, or comprises between 80 wt% vegetable oil and the 20 wt% microbial cells, or comprises between 90 wt% vegetable oil and the 10 wt% microbial cells.

[0029] The invention is also directed to a method for increasing the onset self-heating temperature of a composition which comprises microbial cells that is rich in LC-PUFA. It is surprisingly found in this invention that by mixing vegetable oil with LC-PUFA containing microbial cells, the onset self-heating temperature of the microbial cells is rendered significantly higher than before the mixing. The onset temperature increases when more than 30 wt% vegetable oil is included in the microbial cells/vegetable oil blend. In one embodiment, unruptured microbial cells are mixed with more than 30% vegetable oil. In another embodiment, the microbial cells is ruptured to release the PUFA oils it contains and thus together with the added vegetable oil to create a homogenized, fluid form of mixture. In the later method, the microbial cells can be either ruptured first and then blended with the > 40 wt% vegetable oil, or blended with the > 40 wt% vegetable oil first and then ruptured. The rupturing step can be conducted by any suitable means, including mechanical means and enzymatic means.

[0030] In one embodiment, the invention is directed to a method for increasing the self heating onset temperature of a composition to at least 250 °C, wherein the composition comprises more than 30 wt% vegetable oil and at least 50 wt% microbial cells, wherein said microbial cells comprise one or more polyunsaturated fatty acid (PUFA) having at least 20 carbon atoms and at least three double bonds, wherein the microbial cells has at least 20 wt% PUFAs, and therein the method comprises mixing the microbial cells with the vegetable oil and rupturing the microbial cells. In another embodiment, the composition comprises more than 35 wt% vegetable oil and at least 50 wt% microbial cells. In another embodiment, the composition comprises more than 40 wt% vegetable oil and at least 50 wt% microbial cells.

[0031] In one embodiment, the microbial cells recited in the method above comprise at least 20 wt.%, for instance at least 25 wt.%, for instance at least 30 wt.%, for instance at least 35 wt.%, for instance at least 40 wt.%, for instance at least 45 wt.%, for instance at least 50 wt.%, for instance at least 55 wt.%, for instance at least 60 wt.%, for instance at least 65 wt.%, for instance at least 70 wt.%, for instance at least 75 wt.%, for instance at least 80 wt.%, for instance at least 90 wt.%, for instance at least 95 wt.% PUFA. In another embodiment, the microbial cells comprise between 20-50 wt.%, 20-30 wt.%, 20-40 wt.%, 20-50 wt.%, 20-60 wt.%, between 30-70 wt.%, between 40-60 wt.%, or between 45-55 wt.% PUFAs. In one embodiment, the weight of the microbial cells is referred to as the dry cell weight of a biomass. Such biomass can be algal cells or any other PUFA-containing microbial cells.

[0032] In another embodiment of the invention, the composition recited in the method described above comprises at least 35 wt% vegetable oil and at least 50 wt% microbial cells. In an embodiment of the invention, the composition comprises at least 40 wt% vegetable oil and at least 50 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 90 wt% vegetable oil and between 10 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 90 wt% vegetable oil and between 10 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 80 wt% vegetable oil and between 20 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 70 wt% vegetable oil and between 30 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 60 wt% vegetable oil and between 40 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 30 wt% to 50 wt% vegetable oil and between 50 wt% and 70 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 80 wt% vegetable oil and between 20 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 70 wt% vegetable oil and between 30 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 60 wt% vegetable oil and between 40 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between 40 wt% to 50 wt% vegetable oil and between 50 wt% and 60 wt% microbial cells. In another embodiment, the composition comprises between at least 30 wt% vegetable oil and the remainder wt% microbial cells. In another embodiment, the composition comprises between at least 35 wt% vegetable oil and the remainder wt% microbial cells. In another embodiment, the composition comprises between at least 40 wt% vegetable oil and the remainder wt% microbial cells. In some specific embodiments, the composition comprises between 40 wt% vegetable oil and the 60 wt% microbial cells, or comprises between 35 wt% vegetable oil and the 65 wt% microbial cells, or comprises between 45 wt% vegetable oil and the 55 wt% microbial cells, or comprises between 45 wt% vegetable oil and the 55 wt% microbial cells, or comprises between 50 wt% vegetable oil and the 50 wt% microbial cells, or comprises between 60 wt% vegetable oil and the 40 wt% microbial cells, or comprises between 70 wt% vegetable oil and the 30 wt% microbial cells, or comprises between 80 wt% vegetable oil and the 20 wt% microbial cells, or comprises between 90 wt% vegetable oil and the 10 wt% microbial cells.

[0033] In one embodiment, the microbial cells are ruptured. In another embodiment, the microbial cells are unruptured. In another embodiment, the microbial cells biomass. The microbial cells may be of the genus Mortierella , Schizochytrium , Thraustochytrium , Aurantiochytrium , or Crypthecodinium .

[0034] In one embodiment, the above described PUFAs is one or more type of long chain

PUFAs. In another embodiment, the above described PUFAs is an w-3 or an w-6 PUFA. In another embodiment, the above described PUFAs is one or more PUFA selected from selected from dihomo-y-linolenic acid (DGLA, 20:3 w-6), arachidonic acid (ARA, 20:4 w-6), eicosapentaenoic acid (EPA, 20:5 w-3), docosahexaenoic acid (DHA: 22:6 w-3), docosapentaenoic acid (DPA 22:5 w-3, or DPA 22:5, w-6).

[0035] LC-PUFAs described in this application are fatty acids that contain at least 3 double bonds and have a chain length of 20 or more carbons. Polyunsaturated fatty acids (PUFAs) are classified based on the position of the first double bond from the methyl end of the fatty acid; omega-3 (n-3) fatty acids contain a first double bond at the third carbon, while omega-6 (n-6) fatty acids contain a first double bond at the sixth carbon. For example, docosahexaenoic acid (DHA) is an omega-3 long chain polyunsaturated fatty acid (LC-PUFA) with a chain length of 22 carbons and 6 double bonds, often designated as "22:6n-3." In one embodiment, the PUFA is selected from an omega-3 fatty acid, an omega-6 fatty acid, and mixtures thereof. In another embodiment, the PUFA is selected from LC-PUFAs. In a still further embodiment, the PUFA is selected from docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DP A), arachidonic acid (ARA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA), stearidonic acid (SDA), and mixtures thereof. In another embodiment, the PUFA is selected from DHA, ARA, and mixtures thereof. In a further embodiment, the PUFA is DHA. In yet a further embodiment, the PUFA is ARA.

[0036] As used herein, a "cell" refers to an oil-containing biomaterial, such as biomaterial derived from oleaginous microorganisms. Oil produced by a microorganism or obtained from a microbial cell is referred to as "microbial oil". In one embodiment, microbial oil refers to a crude oil extracted from the biomass of the microorganism with or without further processing. Oil produced by algae and/or fungi is also referred to as algal and/or fungal oil, respectively.

[0037] As used herein, a "microorganism" refers to organisms such as algae, bacteria, fungi, yeast, protist, and combinations thereof, e.g., unicellular organisms. In some embodiments, a microbial cell is a eukaryotic cell. A microbial cell includes, but is not limited to, golden algae (e.g., microorganisms of the kingdom Stramenopiles ); green algae; diatoms; dinoflagellates (e.g., microorganisms of the order Dinophyceae including members of the genus Crypthecodinium such as, for example, Crypthecodinium cohnii or C. cohnii), microalgae of the order Thraustochytriales; yeast ( Ascomycetes or Basidiomycetes); and fungi of the genera Mucor, Mortierella, including but not limited to Mortierella alpina and Mortierella sect , schmuckeri , and Pythium , including but not limited to Pythium insidiosum.

[0038] In one embodiment, the microorganisms are from the genus Mortierella , genus

Crypthecodinium , or order Thraustochytriales. In a still further embodiment, the microbial cells are from Crypthecodinium cohnii. In yet an even further embodiment, the microbial cells are selected from Crypthecodinium cohnii , Mortierella alpina , genus Thraustochytrium , genus Schizochytrium , and mixtures thereof.

[0039] In a still further embodiment, the microorganisms include, but are not limited to, microorganisms belonging to the genus Mortierella , genus Conidioholus , genus Pythium , genus Phytophthora , genus Penicillium , genus Cladosporium , genus Mucor, genus Fusarium , genus Aspergillus , genus Rhodotorula , genus Entomophthora , genus Echinosporangium, and genus Saprolegnia. In another embodiment, ARA is obtained from microbial cells from the genus Mortierella , which includes, but is not limited to, Mortierella elongata, Mortierella exigua, Mortierella hygrophila , Mortierella alpina , Mortierella schmuckeri , and Mortierella minutissima. In a still further embodiment, the microbial cells are from Mortierella alpina.

[0040] In an even further embodiment, the microbial cells are from microalgae of the order

Thraustochytriales, which includes, but is not limited to, the genera Thraustochytrium (species include arudimentale , aureum , benthicola , globosum, kinnei , motivum , multirudimentale , pachydermum , proliferum , roseum, striatum ); the genera Schizochytrium (species include aggregation, limnaceum , mangrovei, minutum , octosporum ); the genera Ulkenia (species include amoeboidea , kerguelensis , minuta , profunda , radiate , sailens , sarkariana, schizochytrops , visurgensis, yorkensis ); the genera Aurantiacochytrium the genera ()blongichytrium the genera Sicyoidochytiunr, the genera Parientichytrium ; the genera Botryochytrium ; and combinations thereof. In another embodiment, the microbial cells are from the order Thraustochytriales. In yet another embodiment, the microbial cells are from Thraustochytrium. In still a further embodiment, the microbial cells are from Schizochytrium. In a still further embodiment, the microbial cells are chosen from genus Mortierella , Schizochytrium , Thraustochytrium , Aurantiochytrium , Crypthecodinium , or mixtures thereof.

[0041] The vegetable oil used in the present invention can be any vegetable oil or a blend of different vegetable oils. In one embodiment, the vegetable oil is canola oil. In other embodiments, the vegetable oil is selected from a group consisting of canola oil, soybean oil, sunflower seed oil, peanut oil, flaxseed oil, sesame seed oil, corn oil, or a combination of the above.

EXAMPLES

[0042] Example 1

[0043] In this example, sample mixtures A through G containing different weight ratio of microbial biomass and vegetable oil were made. See Table 1. The microbial biomass used in this experiment was Schizochytrium strain No. ATCC-20888. It was purchased from DSM Nutritional Products LLC. The biomass is also called DHAgold ^® . The total amount of long chain polyunsaturated fatty acids (PUFA) which have at least 20 carbon atoms and at least three double bonds in the microbial biomass is about 32 wt% of the biomass. The vegetable oil is a food grade Kroger brand pure canola oil purchased from a supermarket. Table 1

[0044] Next, the above mixtures of microbial biomass and vegetable oil were homogenized by grinding in a mortar to disrupt the cells and release the algal oil from the cells. After 10 minutes of grinding, a homogeneous mixture in some of the samples was achieved. Images of the mixtures at different weight ratio are shown in Figure 1. Good flowability was observed in the mixtures which has a biomass/vegetable oil weight ratio of 30%:70% (Fig, 1 A), 40%:60% (Fig. IB), and 50%:50% (Fig. 1C). At a biomass/vegetable oil weight ratio of 60%:40%, the mixture was flowable but is paste-like. At a biomass/vegetable oil weight ratio of 70%:30% (Fig. ID), the mixture has a dough-like texture and thus was not flowable.

[0045] Example 2

[0046] In this example, the self-heating propensity of the mixtures listed in Table 1 in

Example 1 was measured and compared. Specifically, the onset temperature of self-heating for the different mixtures were measured.

[0047] The onset temperature of self-heating was measured using a Gewer Oven test. In this test, the sample mixtures which were prepared in Example 1 were filled into a 6cm ³ test tube. The oven was heated at a rate such that the oven temperature increased linearly at a rate of lK/min The airflow of the oven was set to 2L/min. The test protocol described in VDI-Guideline 2263 was followed.

[0048] The onset temperature of self-heating is the first temperature at which the sample heats up faster inside the test vessel than the pre-heated air in the oven. Such “spike”, like the one shown Fig. 2 at the time point of a little over 2 hours, indicated the first occurrence of spontaneous self-heating of the material in the test tube. The onset temperature of the first self-heating event of mixtures A, B, D, E, F, and G was measured and is shown in Table 2. Table 2

[0049] It was observed, as shown in Figs. 2-7, that when a composition contains between

100 wt% and 70 wt% DHAgold ^® microbial biomass and the remainder wt% of canola oil, the onset temperature of self-heating was maintained at about 150 °C. When the DHAgold ^® microbial biomass was lowered to 70% and the canola oil was increased to more than 30%, the onset temperature of self-heating increased about 150 °C to about 300 °C. Further increasing the wt% of canola oil and decreasing the wt% of DHAgold ^® microbial biomass did not significantly change the onset temperature.