Method for extracting oil from microbial biomass with a press

Abstract

The current invention relates to a method for extracting oil from a yeast biomass comprising the steps of: (i) drying the yeast biomass, wherein the drying is carried out in a contact dryer, wherein in the contact dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, (ii) feeding the dried yeast biomass to a press thereby obtaining a yeast oil containing fraction, wherein the contact dryer and the press are arranged in-line, such that the dried yeast biomass is directly fed to the press.

Description

[0001] METHOD FOR EXTRACTING OIL FROM MICROBIAL BIOMASS WITH A PRESS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for extracting oil from microbial biomass.

[0004] BACKGROUND

[0005] One of the methods to extract oil from microbial biomass is (screw) pressing, which requires dry, solid material as its feed.

[0006] Cell wall rupture is a significant challenge hindering microbial oil extraction, that affects process design of both solvent and mechanical extraction systems. It can impede the profitability of microbial oil production when additional unit operations must be incorporated in the process to allow oil yield. Such cell disruption technologies are capital and energy intensive, such as bead milling or high-pressure homogenization.

[0007] Seen from a different angle, mechanical oil extraction requires the following phenomena to happen: Biomass drying, cell disruption, oil transport to the outside of the cell, and oil recovery in a concentrated stream. The current state of the art for microbial oil extraction distributes these tasks between many unit operations, at least one per phenomenon, so the resulting process is not profitable to produce commodity-priced oil.

[0008] Another problem is that the morphology of the dry material must be amenable to pressing, i.e., cell disruption is not the only condition for yield during mechanical extraction, but also material density, porosity, hardness, and crystallization degree affect oil yield from pressing. Our solution produces an optimal morphology, in porosity and crystallization degree, to improve yield from mechanical extraction.

[0009] Finally, drying procedures exist that mistreat the biomass to a degree that diminishes both the oil and proteins market value. This restricts the drying procedure to have either low temperature or very low time exposure, which challenges its viability to achieve the right moisture content within reasonable processing times. W02019030072 discloses a process for extracting lipids produced by fermentation of microbial cells from a fermentation medium. W02024054110 describes a method for producing an oil composition from oleaginous yeasts.

[0010] The solutions deployed by the prior art include:

[0011] 1. Adding wet milling procedures before drying the biomass. High-pressure homogenization, bead beating, ball mills, etc. have been tried, at the expense of high capital and energy expenses.

[0012] 2. Adding sample preparation steps after drying, as is done with oil seeds: conditioning, flaking, extrusion, expansion, or combinations thereof are performed on low-moisture material to achieve cell disruption and morphology conditioning to allow either mechanical or solvent-driven oil extraction.

[0013] 3. Submitting the press cake to solvent extraction to mitigate the low yield of pressing. The facilities cost and the consumer perception and environmental disadvantages of using solvent technology are very high.

[0014] The present invention aims to resolve at least some of the problems and disadvantages mentioned above.

[0015] SUMMARY OF THE INVENTION

[0016] The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a method for extraction of oil according to claim 1.

[0017] Particularly, the invention provides a method for extracting oil from a microbial biomass comprising the steps of drying the microbial biomass, wherein the drying is carried out in a contact dryer, wherein in the contact dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, (ii) feeding the dried microbial biomass to a press thereby obtaining a microbial oil containing fraction, wherein the contact dryer and the press are arranged in-line, such that the dried microbial biomass is directly fed to the press.

[0018] This solution avoids the introduction of an excessive number of unit operations to prompt the phenomena listed above and achieves it with a clever combination of only two procedures: contact drying is enough for drying and a sufficient degree of cell rupturing and material porosity, that allows high enough oil yields from screw pressing alone. In other words, the procedure known as "contact drying", such as for example drum drying, when applied to cell-wall-endowed microbes, prepares the bulk biomass for mechanical extraction by puncturing the cells and producing a porous structure, besides effectuating the already needed drying.

[0019] It has been found that no heat-related preparation steps, such as heat conditioning, after drying are needed.

[0020] The method has been proven especially effective with yeast biomass.

[0021] DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention concerns a method for extracting oil from microbial biomass.

[0023] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0024] As used herein, the following terms have the following meanings:

[0025] The expression "oleaginous" as used herein refers to material, e.g., a microorganism, which contains a significant component of oils, or which is itself substantial composed of oil. An oleaginous microorganism can be one that is naturally occurring or synthetically engineered to generate a significant proportion of oil.

[0026] The expression "oleaginous yeast" as used herein refers to a collection of yeast species that can accumulate a high proportion of their biomass as lipids (namely greater than 20% of dry cell mass). An oleaginous yeast can be one that is naturally occurring or synthetically engineered to generate a significant proportion of oil.

[0027] For the purposes of this disclosure "microbial oil" and "microbial fat" refer to microbial lipids produced by the microbial biomass, preferably the oleaginous microbial biomass.

[0028] The term "drying" as used herein refers to the removal of moisture from the microbial biomass, typically by applying heat, thereby lowering the moisture content. The term "moisture content" as used herein refers to the percentage of water content present in the yeast biomass, measured by weight (wt.%).

[0029] The term "contact dryer" as used herein refers to a device or apparatus in which heat is transferred to the microbial biomass primarily through direct contact with a heated surface.

[0030] The term "press" as used herein refers to a mechanical device designed to apply pressure to the dried microbial biomass to extract oil, thereby yielding an oilcontaining fraction.

[0031] The term "in-line" as used herein refers to the arrangement of equipment, positioned such that a continuous sequence of operations or machines is achieved with a direct transfer from one to the other.

[0032] The expression "solid fat content" (SFC) refers to the proportion of fat that remains solid at a specific temperature. It is preferably measured using Nuclear Magnetic Resonance (NMR) spectroscopy, a technique outlined in the ISO 8292:2008 standard, which provides a rapid and non-destructive means of quantifying the solid and liquid phases of fats.

[0033] "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

[0034] "About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

[0035] "Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

[0036] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0037] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

[0038] The expression "% by weight", "weight percent", "%wt" or "wt%", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation.

[0039] Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

[0040] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

[0041] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0042] In a first aspect, the invention relates to a method for extracting oil from a microbial biomass. In an embodiment, the microbial biomass is a yeast biomass.

[0043] In a preferred embodiment, the method comprises the steps of: i. drying the microbial biomass, wherein the drying is carried out in a contact dryer, wherein in the contact dryer heat is transferred to the microbial biomass primarily through direct contact with a heated surface, and ii. feeding the dried microbial biomass to a press thereby obtaining a microbial oil containing fraction.

[0044] In an embodiment, the dried microbial biomass is fed to the press, preferably directly fed. In a further embodiment, the dried yeast biomass is, preferably directly, fed to the press, without additional heating steps.

[0045] Preferably the contact dryer and the press are arranged in-line, such that the dried microbial biomass is directly fed to the press. This avoids the introduction of an excessive number of unit operations to prompt the phenomena listed above and achieves it with a combination of contact drying and pressing. Contact drying is enough for drying and a sufficient degree of cell rupturing and material porosity, that allows high enough oil yields from screw pressing alone. In other words, contact drying, when applied to cell-wall-endowed microbial biomass, prepares the bulk biomass for mechanical extraction by puncturing the cells and producing a porous structure, besides effectuating the already needed drying.

[0046] The contact dryer and the press are preferably arranged in-line, such that the dried yeast biomass is directly fed to the press, without any intermediate processing steps, such as heating steps.

[0047] In an embodiment, the contact dryer is positioned above the inlet of the press to aid the transfer of product significantly. The use of a contact dryer makes that the energy for evaporation is provided by conduction, not by convection. This means that water does not first transport to the surface of the film and there finds energy to evaporate, as it happens during e.g. ventilation drying, but it directly receives the energy to evaporate while it remains inside the cells.

[0048] Furthermore, no additional movement or shear is present, that could smear the oil into the proteins and other cellular debris; therefore, oil bodies, that are devoid of volatile compounds, do not diminish their particle size. This is an advantage because the entire oil droplet can be pressed out of the cells through the created pore.

[0049] In an embodiment, the drying time may range from 1 to 30 seconds, preferably from 1 to 25 seconds, more preferably from 1 to 20 seconds, and even more preferably between 1 and 15 seconds. In another or further embodiment, the drying process is carried out for a period between 5 and 15 seconds. In a more specific embodiment, the drying period may range from 5 to 10 seconds, or even from 5 to 7 seconds, which has been found to provide an optimal balance between effective moisture removal and maintaining biomass quality.

[0050] It was found that this fast drying process in the contact dryer produces a porous material, which improves pressability. In contrast, slower drying methods, such as oven drying or contact drying for longer periods, result in a denser and more compact microbial biomass, which is less suitable for efficient processing.

[0051] In a preferred embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying a yeast biomass, wherein the drying is carried out in a contact dryer, wherein in the contact dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying process is carried out for a period between 1 and 20 seconds, preferably between 5 and 15 seconds, and ii. feeding the dried yeast biomass to a press thereby obtaining a yeast oil containing fraction, wherein the dried yeast biomass is, preferably directly, fed to the press, without additional heating steps. In an embodiment, the contact dryer is selected from the group consisting of a drum dryer, a paddle dryer, a disc dryer, a conical screw dryer, a rotary vacuum dryer, a plate dryer, a double cone vacuum dryer, and a rotary kiln dryer.

[0052] In a preferred embodiment, the contact dryer is a drum dryer. The microbial biomass is spread over the surface of a rotating drum that is internally heated by steam or another thermal fluid. The water or solvent in the material evaporates by direct contact with the heated surface.

[0053] The drum dryer offers several benefits, especially when used for microbial biomass drying. The drum dryer is efficient at reducing the moisture content to a specific level without needing to achieve complete drying, which can be advantageous for biomass applications where only partial drying is needed to prepare the material for subsequent processing, resulting in a higher moisture content than typically needed in known techniques. This partial drying reduces energy consumption and helps preserve the quality of the biomass, avoiding degradation of sensitive components. The drum dryer also allows for high throughput and continuous operation, making it an economical and practical choice for handling large volumes of biomass with varying moisture content. The drum dryer is also beneficial as the microbial biomass is preheated to boiling temperature before significant evaporation onsets. Furthermore, the contact dryers, and especially the drum dryer, allows short drying periods, which has been found advantageous to the pressability of the biomass.

[0054] In another embodiment, the contact dryer is a paddle dryer. This dryer comprises two parallel shafts with intermeshing paddles that agitate the microbial biomass. The hollow paddles are internally heated, and the material is dried through heat transfer from the paddles and the walls.

[0055] In another embodiment, the contact dryer is a disc dryer. Similar to the paddle dryer, but with rotating discs instead of paddles. The discs are heated internally, and the microbial biomass is dried via contact with these heated surfaces.

[0056] In another embodiment, the contact dryer is a conical screw dryer (also called a Nauta Dryer). This dryer is a vertical, conical vessel with an internally heated screw agitator that moves microbial biomass gently upwards. The conical walls are heated, and the screw continually mixes the product to promote even drying. In another embodiment, the contact dryer is a rotary vacuum dryer. This is a cylindrical dryer that rotates under vacuum, which reduces the boiling point of the moisture. The jacket of the drum is heated by steam or hot water, and the microbial biomass is indirectly heated, promoting solvent evaporation at lower temperatures.

[0057] In another embodiment, the contact dryer is a plate dryer. The microbial biomass is spread on heated plates that are stacked vertically, with a scrapper or conveyor system that moves the product across the plates.

[0058] In another embodiment, the contact dryer is a double cone vacuum dryer. This type of dryer has a double cone shape and rotates under a vacuum to reduce drying temperature. The walls are heated, and the microbial biomass tumbles gently, which results in effective contact with the heated surface.

[0059] In another embodiment, the contact dryer is a rotary kiln dryer. While rotary kilns are often thought of as direct dryers, they can also be used for contact drying when the microbial biomass is exposed to the heated shell rather than directly to the hot gas.

[0060] In an embodiment, the heated surface of the contact dryer has a temperature of at least 100°C, preferably at least 120°C, or even at least 130°C or at least 135 °C. In another or further embodiment, the heated surface of the contact dryer has a temperature of between 100 and 200°C, preferably between 120 and 180°C, or even between 130 and 160°C or between 135 and 155°C.

[0061] In another or further embodiment, the microbial biomass reaches a temperature of at least 75°C, preferably at least 80°C, or even at least 85°C or even more preferably at least 90°C, even more preferably at least 95°C, even more preferably at least 100°C. In another or further embodiment, the microbial biomass reaches a temperature of between 75 and 175°C, preferably between 85 and 150°C, or even between 95 and 140°C or between 100 and 135°C.

[0062] In an embodiment, the dried microbial biomass is cooled prior to feeding to the press. Preferably, the dried microbial biomass is cooled with a dry air flow. In an embodiment, the dry air has a temperature of at most 40°C, more preferably at most 30°C, even more preferably at most 20°C, or even at most 10°C. Residual moisture can also be removed by convection. The dried microbial biomass can be cooled while it is transferred to the press. The dried microbial biomass preferably has a temperature of between 20 and 60°C prior to feeding to the press. In a further embodiment, the dried microbial biomass preferably has a temperature of between 25 and 50°C, more preferably between 30 and 50°C, or even between 35 and 45°C.

[0063] In another or further embodiment, the heated surface is heated with steam or another thermal fluid including hot oil, molten salts, or pressurized water, preferably the heated surface is heated with steam. The steam preferably has a pressure of at least 1.5 bar, preferably at least 1.6 bar, more preferably at least 1.7 bar, even more preferably at least 1.8 bar, even more preferably at least 1.9 bar, or even at least 2.0 bar.

[0064] In another or further embodiment, the steam has a pressure of at most 5 bar, preferably at most 4.9 bar, more preferably at most 4.8 bar, even more preferably at most 4.7 bar, even more preferably at most 4.6 bar, or even at most 4.5 bar. In another or further embodiment, the steam has a pressure of between 1.5 and 10 bar, preferably between 1.5 and 7.5 bar, or even between 1.5 and 5 bar or 2.0 and 4.5 bar.

[0065] In an embodiment, the contact dryer is operated in such a way that the microbial biomass forms a film on the heated surfaces of the contact dryer, wherein the film thickness is at most 2 mm, preferably at most 1.5 mm, and even more preferably at most 1 mm. This thin film allows for efficient heat transfer and rapid moisture evaporation, ensuring that the biomass is evenly dried without overheating or damaging the material. The use of a film with a maximum thickness of 1 mm has been found to improve drying uniformity and reduce energy consumption. This thin film allows for efficient heat transfer and rapid moisture evaporation, ensuring that the biomass is evenly dried without overheating or damaging the material.

[0066] In an embodiment, the rotating drum acts on the microbial biomass with a centrifugal force of between 0.01 and 1 N / kg microbial biomass, preferably between 0.01 and 0.5 N / kg, preferably between 0.05 and 0.3 N / kg.

[0067] In another or further embodiment, the contact dryer is a drum dryer comprising a rotating drum, wherein the rotating drum as a diameter at least 0.5 m, and has a rotation speed of at most 10 RPM. In another or further embodiment, the rotating drum as a diameter between 0.5 and 5 m, preferably between 0.5 and 2 m, and has a rotation speed of between 1 and 10 RPM, preferably between 2.5 and 10 RPM.

[0068] In an embodiment, the dried microbial biomass has a moisture content of at least 1.5 wt.%, preferably at least 2 wt.%, more preferably at least 2.5 wt.%, even more preferably at least 3 wt.%, at least 3.5 wt.%, or even at least 4 wt.% or at least 4.5 wt.%, even more preferably at least 5 wt.%.

[0069] It was found that a higher moisture content than used in known techniques give good results. No extra heat-conditioning step was necessary to extract the microbial oil efficiently.

[0070] In another or further embodiment, the dried microbial biomass has a moisture content of between 1.5 and 10 wt.%, preferably between 2 and 10 wt.%, more preferably between 2.5 and 10 wt.%, even more preferably between 3 and 10 wt.%, even more preferably between 3.5 and 10 wt.%, even more preferably between 4 and 10 wt.%, more preferably between 4.5 and 10 wt.%, more preferably between

[0071] 5 and 10 wt.%, more preferably between 5.5 and 10 wt.%, more preferably between

[0072] 6 and 10 wt.%.

[0073] In an embodiment, the microbial biomass is dewatered prior to the drying step. The dewatering can be carried out by any mechanical separation technique that reduces the free water content of the microbial biomass, without affecting the microstructure that is formed during the subsequent contact drying. Suitable techniques include centrifugation, decanting, sedimentation or filtration methods. The purpose of the dewatering step is to remove bulk liquid and to obtain a biomass with a consistency that can be continuously applied onto the heated surface of the contact dryer.

[0074] In an embodiment, the microbial biomass is dewatered by centrifugation prior to the drying step. Centrifugation provides a robust and energy efficient means of removing bulk water without imposing shear or membrane related stresses on the biomass. It produces a uniform and homogeneous retentate that can be applied as a thin and continuous film onto the heated surface of the contact dryer. This uniformity has been found to improve heat transfer during the short drying period and to promote the formation of the porous dried structure that characterizes the present method. Centrifugation does not alter the intracellular lipid distribution and does not induce cell rupture. In an embodiment, the dewatered microbial biomass has a moisture content between 80 and 60 wt.%, preferably between 75 and 65 wt.%.

[0075] In an embodiment, the press is selected from the group consisting of a screw press, a piston press, and a hydraulic press. Among these options, a screw press is particularly preferred.

[0076] The screw press or "expeller press" utilizes a rotating screw to convey the biomass through a cylindrical chamber. The biomass is fed into a press head, optionally via a hopper, where it encounters the screw, which gradually compresses the material as it moves along the length of the chamber. A nozzle choke is positioned at the discharge end of the press, providing resistance to create backpressure, which enhances the extraction process. As the biomass moves through the press, the screw applies increasing pressure, forcing the oil out through perforations in the chamber. The screw press can manage the higher moisture content, minimizing clogging, and effectively separates oil while compacting the residual solids into a press cake.

[0077] In an embodiment the screw press is a twin-screw press, which involves the use of two interlocking screws rotating either in the same direction or counter-rotating. In an embodiment, the screw press is a conical screw press, wherein the press is provided with a tapered shaft, producing axial pressure as the screw's groove volume decreases towards the press head.

[0078] In some embodiments, a piston press may be used. The piston press operates by using a reciprocating piston to apply pressure on the biomass in a confined chamber. Although the process is not continuous like a screw press, it can be advantageous for small-scale operations where precise control over the pressure is needed.

[0079] In some embodiments, a hydraulic press may be used. The hydraulic press applies force using hydraulic cylinders, allowing for precise control over the pressure applied. This method is advantageous for delicate biomass that could be damaged by excessive shearing or heat. Hydraulic presses are also well-suited for smaller operations where the quality of the extracted oil is of high importance, as they allow for a more gentle extraction process compared to mechanical screw presses.

[0080] The pressing step involves subjecting pressure sufficient to extract oil from the dried microbial biomass. In some embodiments, the pressing step will involve subjecting the conditioned feedstock to at least 689 bar (10,000 psi) of pressure. In some embodiments, the pressing step involves the application of pressure for a first period of time and then application of a higher pressure for a second period of time. This process may be repeated one or more times ("oscillating pressure"). In some embodiments, more than 5 cycles of oscillating pressure are applied. In some embodiments, one or more of the subsequent cycles may exert an average pressure that is higher than the average pressure exerted in one or more earlier cycles.

[0081] In an embodiment, the press head temperature is between 50 and 200°C, more preferably between 75 and 160°C, or even between 80 and 150°C. In another or a further embodiment, the screw press rotates at a speed of between 1 and 100 RPM, or even between 5 and 50 RPM.

[0082] The press is preferably not actively heated. In an embodiment, the press is heated by due to the mechanical energy that is converted into heat. The temperature along the screw and barrel increases considerably from the inlet (hopper) to the outlet (head). I stated press head temperatures in the first point's comment, while these temperatures on point 9 cover the full press' barrel.

[0083] In an embodiment, the press reaches temperatures of between 30°C and 150°C

[0084] In an embodiment, a press aid is added to the microbial biomass or the dried microbial biomass. In some cases, the press aid can be added to the microbial biomass after it has been dried, but not yet conditioned. In such cases, it may advantageous to mix the dry microbial biomass with the desired amount of the press aid and then condition the microbial biomass and the press aid together before feeding to a press. In other cases, the press aid can be added to a microbial biomass before the microbial biomass has been subjected to drying.

[0085] In an embodiment, the bulking agent has an average particle size of less than 1.5 mm. In some embodiments, the bulking agent or press aid has a particle size of between 50 microns and 1.5mm. In other embodiments, the press aid has a particle size of between 150 microns and 350 microns. In some embodiments, the bulking agent is a filter aid. In some embodiments, the bulking agent is selected from the group consisting of cellulose, corn stover, dried rosemary, soybean hulls, spent biomass (biomass of reduced lipid content relative to the biomass from which it was prepared), including spent microbial biomass, sugar cane bagasse, and switchgrass. The method preferably does not comprise a heat conditioning step between step (i) and step (ii). It has been found that lowering the moisture content further after drying is not necessary and only generates excess costs and lower efficiency.

[0086] The microbial biomass is preferably a fermented microbial biomass. During the fermentation stage, the cell density and the microbial oil in the cell suspension will increase due to microbial growth. At a certain point, the microbial cell will have exhausted one or more nutrients required for further microbial growth and oil production. At such point, the oil may not further increase in the cell suspension and the oil may be extracted according to an embodiment of the method described herein. Hence, in some embodiments, the microbial biomass has a cell density selected from the range of 107 - 1011 cells / ml, such as from the range of 108 - 1010 cells / ml.

[0087] The use of oleaginous microorganisms for oil production has many advantages over traditional oil harvesting methods, e.g., palm oil harvesting from palm plants. For example, microbial fermentation (1) does not compete with food production in terms of land utilization; (2) can be carried out in conventional microbial bioreactors; (3) has rapid growth rates; (4) is unaffected or minimally affected by space, light, or climate variations; (5) can utilize waste products as feedstock; (6) is readily scalable; and (7) is amenable to bioengineering for the enrichment of desired fatty acids or oil compositions.

[0088] In an embodiment the microbial biomass comprises between 20 and 80 wt.% oil on a dry matter basis, preferably between 20 and 70 wt.%, more preferably between 30 and 70 wt.%, even more preferably between 40 and 70 wt.%, or even more preferably between 50 and 70 wt.%

[0089] In an embodiment, the biomass is prepared by fermentation of a microorganism selected from the group consisting of microalgae, oleaginous bacteria, oleaginous yeast, and fungi.

[0090] Oleaginous yeast in particular are robust, viable over multiple generations, and versatile in nutrient utilization. They also have the potential to accumulate intracellular lipid content up to greater than 70% of their dry biomass. The microbial biomass comprises preferably an oleaginous yeast. In some embodiments, the yeast may be in haploid or diploid forms. The yeasts may be capable of undergoing fermentation under anaerobic conditions, aerobic conditions, or both anaerobic and aerobic conditions. A variety of species of oleaginous yeast that produce suitable oils and / or lipids can be used to extract oil in accordance with the present disclosure. In some embodiments, the oleaginous yeast in the microbial biomass naturally produces high (20%, 25%, 50% or 75% of dry cell weight or higher) levels of suitable oils and / or lipids. In some embodiments, the oleaginous yeast comprises cells that are capable of producing at least 20%, 25%, 50% or 75% or more oil by dry weight.

[0091] Suitable species of oleaginous yeast for extracting microbial oil according to the of the present disclosure include, but are not limited to Candida apicola, Candida sp., Cryptococcus albidus, Cryptococcus curvatus, Cryptococcus terricolus, Cutaneotrichosporon oleaginosus, Debaromyces hansenii, Endomycopsis vernalis, Geotrichum carabidarum, Geotrichum cucujoidarum, Geotrichum histeridarum, Geotrichum silvicola, Geotrichum vulgare, Hyphopichia burtonii, Lipomyces lipofer, Lypomyces orentalis, Lipomyces starkeyi, Lipomyces tetrasporous, Pichia mexicana, Rodosporidium sphaerocarpum, Rhodosporidium toruloides Rhodotorula aurantiaca, Rhodotorula dairenensis, Rhodotorula diffluens, Rhodotorula glutinus, Rhodotorula glutinis var. glutinis, Rhodotorula gracilis, Rhodotorula graminis, Rhodotorula minuta, Rhodotorula mucilaginosa, Rhodotorula mucilaginosa, Rhodotorula terpenoidalis, Rhodotorula toruloides, Sporobolomyces alborubescens, Starmerella bombicola, Torulaspora delbruekii, Torulaspora pretoriensis, Trichosporon behrend, Trichosporon brassicas, Trichosporon domesticum, Trichosporon laibachii, Trichosporon loubieri, Trichosporon loubieri, Trichosporon montevideense, Trichosporon pullulans, Trichosporon Sp., Wickerhamomyces, Yarrowia lipolytica, and Zygoascus meyerae.

[0092] In an embodiment, said yeast is from selected from: Cutaneotrichosporon genus, Lipomyces genus, Rhodotorula genus and Metschnikowia genus. In an embodiment, said yeast is from selected from : Cutaneotrichosporon genus, Lipomyces starkeyi, Rhodotorula toruloides and Metschnikowia pulcherrima. In an embodiment, said yeast is from selected from : Cutaneotrichosporon oleaginosus, Lipomyces starkeyi, Rhodotorula toruloides and Metschnikowia pulcherrima.

[0093] In an embodiment, said yeast is from the Cutaneotrichosporon genus. Said Cutaneotrichosporon yeast is preferably Cutaneotrichosporon oleaginosus. Cutaneotrichosporon oleaginosus may be capable of growing and producing yeast oil at (relatively) low temperatures. Further, Cutaneotrichosporon oleaginosus may provide particularly high yeast oil yields and / or yeast oil titers compared to other species of yeast. Hence, Cutaneotrichosporon oleaginosus is particularly appropriate to provide a microbial oil.

[0094] The use of Cutaneotrichosporon provides an additional advantage in that this yeast forms a biomass that is particularly well suited for mechanical oil recovery after drying. In practice, dried biomass originating from Cutaneotrichosporon oleaginosus has been observed to exhibit excellent pressability and to deliver high oil yields when subjected to the pressing step described herein.

[0095] In a particularly preferred embodiment said microbial biomass comprises an oleaginous yeast, wherein said oleaginous yeast is Cutaneotrichosporon oleaginosus.

[0096] The extracted oil containing fraction can be used for producing derivatives, such as triglycerides, diglycerides, monoglycerides, free fatty acids, fatty acid salts, glycerin, fatty esters, fatty alcohols, fatty amines, fatty acid methyl esters, amide carboxylates, FOH ethoxylates, FOH sulfates, amine oxides, betaines, quats, sophorolipids, ether sulfates, or a combination thereof. These derivatives can for example subsequently be used in food products, feed products, pet feed, personal care products, home care products, fuels, pharmaceuticals, or a combination thereof.

[0097] In an embodiment, the extracted oil containing fraction is used in food products, feed products, pet feed, personal care products, home care products, fuels, pharmaceuticals, or a combination thereof. More specifically, the extracted oil containing fraction can be used in bakery products; confectionery items; dairy alternatives; frying oils; spreads and margarines; salad dressings; nutraceuticals; animal feed; pet food; personal care products; pharmaceuticals; biofuels; industrial lubricants; surfactants; soaps and detergents.

[0098] The extracted oil containing fraction may serve as palm oil alternatives and may be processed and / or derivatized by any number of means known in the art. The extracted oil containing fraction and / or derivatives thereof may be used in a variety of downstream products of interest, such as food products, feed products, pet feed, personal care products, home care products, fuels, pharmaceuticals, or a combination thereof.

[0099] The obtained oil containing fraction preferably has a solid fat content at 20°C of between 5 and 80% by weight, preferably between 10 and 80% by weight, more preferably between 15 and 80% by weight, more preferably between 20 and 80% by weight, even more preferably between 25 and 80% by weight, even more preferably between 30 and 80% by weight.

[0100] In an embodiment, said oil containing fraction has a solid fat content at 20°C of between 5 and 80% by weight, preferably between 5 and 70% by weight, more preferably between 5 and 60% by weight, even more preferably between 5 and 50% by weight, even more preferably between 5 and 40% by weight, even more preferably between 5 and 30% by weight.

[0101] In an embodiment, said oil containing fraction has a solid fat content at 20°C of between 5 and 30% by weight, preferably between 5 and 25% by weight, more preferably between 5 and 20% by weight, even more preferably between 10 and 20% by weight.

[0102] In an embodiment, said oil containing fraction has a solid fat content at 20°C of between 5 and 80% by weight, preferably between 10 and 70% by weight, more preferably between 15 and 60% by weight, even more preferably between 20 and 50% by weight, even more preferably between 25 and 40% by weight.

[0103] In another or further embodiment, said oil containing fraction has a solid fat content at 20°C of at least 5% by weight, preferably at least 10% by weight, more preferably at least 15% by weight.

[0104] In an embodiment, said oil containing fraction has a solid fat content at 10°C of at least 25% by weight, preferably at least 30% by weight, more preferably at least 35% by weight.

[0105] In an embodiment, said oil containing fraction has a solid fat content at 10°C of between 25 and 90% by weight, preferably between 30 and 85% by weight, preferably between 35 and 85% by weight.

[0106] In an embodiment, said oil containing fraction has a solid fat content at 10°C of between 25 and 60% by weight, preferably between 25 and 50% by weight, preferably between 30 and 50% by weight, preferably between 30 and 45% by weight, more preferably between 35 and 45% by weight. In an embodiment, said oil containing fraction has a solid fat content at 25°C of at most 5% by weight, preferably at most 1% by weight, preferably at most 0.5% by weight, preferably at most 0.1% by weight.

[0107] In an embodiment, said oil containing fraction has a solid fat content at 30°C of at most 5% by weight, preferably at most 1% by weight, preferably at most 0.5% by weight, preferably at most 0.1% by weight, more preferably at most 0.01% by weight.

[0108] In a preferred embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying a yeast biomass, wherein the drying is carried out in a contact dryer, preferably a drum dryer, wherein in the contact dryer, preferably the drum dryer, heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying process is carried out for a period between 1 and 20 seconds, preferably between 5 and 15 seconds, and ii. feeding the dried yeast biomass to a press, preferably a screw press, thereby obtaining a yeast oil containing fraction, wherein the dried yeast biomass is, preferably directly, fed to the press, without additional heating steps.

[0109] In an embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a contact dryer, preferably a drum dryer, wherein in the contact dryer, preferably the drum dryer, heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying process is carried out for a period between 1 and 20 seconds, preferably between 5 and 15 seconds, ii. optionally, cooling the dried yeast biomass in a cooling apparatus; iii. feeding the dried yeast biomass to a press, preferably a screw press, thereby obtaining a yeast oil containing fraction, wherein the, optionally cooled, dried yeast biomass is, preferably directly, fed to the press, without additional heating steps, optionally via the cooling apparatus.

[0110] In an embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a contact dryer, preferably a drum dryer, wherein in the contact dryer, preferably the drum dryer, heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying process is carried out for a period between 1 and 20 seconds, preferably between 5 and 15 seconds, ii. optionally, cooling the dried yeast biomass in a cooling apparatus; iii. feeding the dried yeast biomass to a press, preferably a screw press, thereby obtaining a yeast oil containing fraction, wherein the contact dryer, preferably the drum dryer, optionally the cooling apparatus, and the press, preferably the screw press, are arranged in-line, such that the dried yeast biomass is directly fed to the screw press, optionally via the cooling apparatus.

[0111] In an embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying a yeast biomass, wherein the drying is carried out in a drum dryer, wherein in the drum dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, ii. feeding the dried yeast biomass to a screw press thereby obtaining a yeast oil containing fraction, wherein the drum dryer and the press are arranged in-line, such that the dried yeast biomass is directly fed to the press.

[0112] In an embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a drum dryer, wherein in the drum dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the dried yeast biomass has a moisture content of at least 1.5 wt.%, more preferably of at least 4 wt.%, ii. feeding the dried yeast biomass to a screw press thereby obtaining a yeast oil containing fraction, wherein the drum dryer and the press are arranged in-line, such that the dried yeast biomass is directly fed to the press.

[0113] In an embodiment, the method is a method for extracting oil from a yeast biomass comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a drum dryer, wherein in the drum dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying is carried out for a period between 5 and 15 seconds, ii. optionally, cooling the dried yeast biomass in a cooling apparatus, and iii. feeding the dried yeast biomass to a screw press thereby obtaining a yeast oil containing fraction, wherein the drum dryer, optionally the cooling apparatus, and the screw press are arranged in-line, such that the dried yeast biomass is directly fed to the screw press, optionally via the cooling apparatus.

[0114] In an embodiment, the method is conducted in a continuous flow mode. In another embodiment, it is possible that the dried biomass needs to be transported from the dryer to the press, if the dryer and press are not in the same location.

[0115] Optionally, the dried and / or cooled biomass is grinded before feeding to the press. In this way the dried biomass sheets can be chopped up into particles.

[0116] The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended to, nor should they be interpreted to, limit the scope of the invention.

[0117] EXAMPLES

[0118] Example 1

[0119] A cultured Cutaneotrichosporon oleaginosus yeast biomass slurry was dried in a contact drum dryer for a duration of 7 seconds. The resulting dried yeast material was porous and exhibited excellent pressability, as determined by a compression test, which showed a significant reduction in applied force required to achieve a uniform compressed shape. Microscopic analysis revealed a porous vascular-like structure, contributing to its enhanced mechanical handling properties.

[0120] Comparative Example 2

[0121] The same Cutaneotrichosporon oleaginosus yeast biomass slurry was dried in an oven at 80°C for a duration of 4 hours to achieve a comparable final moisture content. The dried material was compact and dense, with limited porosity. Compression testing showed significantly higher force requirements to achieve a uniform compressed shape, indicating poor pressability. Microscopic analysis revealed a closed-cell structure, resulting from the slow drying process.

[0122] Comparative Example 3 The Cutaneotrichosporon oleaginosus yeast biomass slurry was dried in the same conditions as example 1, but for 1 minute. The extended drying time resulted in a denser material with reduced porosity. Compression testing showed moderate pressability, with higher applied force required compared to the 7-second dried sample. Microscopic analysis revealed partial collapse of the porous structure due to prolonged exposure to heat and pressure.

[0123] Similar results were observed for the oleaginous yeasts Lipomyces starkeyi, Rhodotorula toruloides and Metschnikowia pulcherrima, but lesser results were achieved for Yarrowia lipolytica.

[0124] The invention may thus be described according to the following embodiments:

[0125] 1. A method for extracting oil from a yeast biomass comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a contact dryer, wherein in the contact dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, ii. feeding the dried yeast biomass to a press thereby obtaining a yeast oil containing fraction, wherein the dried yeast biomass is fed to the press without additional heating steps.

[0126] 2. Method according to embodiment 1, wherein the press is a screw press.

[0127] 3. Method according to any of the previous embodiments, wherein the contact dryer is a drum dryer.

[0128] 4. Method according to any of the previous embodiments, wherein the drying is carried out for a period between 5 and 15 seconds.

[0129] 5. Method according to any of the previous embodiments, wherein the dried yeast biomass has a moisture content of at least 4 wt.%, preferably at least 5 wt.%.

[0130] 6. Method according to any of the previous embodiments 1-4, wherein the dried yeast biomass has a moisture content of between 1.5 and 10 wt.%.

[0131] 7. Method according to any of the previous embodiments, wherein the dried yeast biomass has a moisture content of between 4 and 10 wt.%.

[0132] 8. Method according to any of the previous embodiments, wherein the dried yeast biomass is cooled prior to feeding to the press.

[0133] 9. Method according to any of the previous embodiments, wherein the method does not comprise a heat conditioning step between drying and pressing. 10. Method according to any of the previous embodiments, wherein the temperature during drying is between 100°C and 135°.

[0134] 11. Method according to any of the previous embodiments, wherein the press is operated at a temperature of between 30°C and 150°C

[0135] 12. Method according to any of the previous embodiments, wherein the contact dryer and the press are arranged in-line, such that the dried yeast biomass is directly fed to the press, without any additional heating steps.

[0136] 13. Method according to any of the previous embodiments, wherein the yeast biomass comprises between 20 and 70 wt.% oil on a dry matter basis.

[0137] 14. Method according to any of the previous embodiments, wherein said yeast oil containing fraction has a solid fat content at 20°C of between 5 and 80 wt.%.

[0138] 15. Method according to embodiment 14, wherein said yeast oil containing fraction has a solid fat content at 20°C of between 5 and 30 wt.%.

[0139] 16. Method according to any of the previous embodiments, wherein the yeast biomass comprises an oleaginous yeast.

[0140] 17. Method according to embodiment 16, wherein said oleaginous yeast is Cutaneotrichosporon oleaginosus .

[0141] 18. Method according to any of the previous embodiments, the method comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a drum dryer, wherein in the drum dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying is carried out for a period between 5 and 15 seconds, ii. optionally, cooling the dried yeast biomass in a cooling apparatus, and iii. feeding the dried yeast biomass to a screw press thereby obtaining a yeast oil containing fraction, wherein the drum dryer, optionally the cooling apparatus, and the screw press are arranged in-line, such that the dried yeast biomass is directly fed to the screw press, optionally via the cooling apparatus.

Claims

CLAIMS1. A method for extracting oil from a yeast biomass comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a contact dryer, wherein in the contact dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, ii. feeding the dried yeast biomass to a press thereby obtaining a yeast oil containing fraction, wherein the dried yeast biomass is fed to the press without additional heating steps.

2. Method according to claim 1, wherein the press is a screw press.

3. Method according to any of the previous claims, wherein the contact dryer is a drum dryer.

4. Method according to any of the previous claims, wherein the drying is carried out for a period between 5 and 15 seconds.

5. Method according to any of the previous claims, wherein the dried yeast biomass has a moisture content of at least 4 wt.%, preferably at least 5 wt.%.

6. Method according to any of the previous claims 1-4, wherein the dried yeast biomass has a moisture content of between 1.5 and 10 wt.%.

7. Method according to any of the previous claims, wherein the dried yeast biomass has a moisture content of between 4 and 10 wt.%.

8. Method according to any of the previous claims, wherein the dried yeast biomass is cooled prior to feeding to the press.

9. Method according to any of the previous claims, wherein the method does not comprise a heat conditioning step between drying and pressing.

10. Method according to any of the previous claims, wherein the temperature during drying is between 100°C and 135°.

11. Method according to any of the previous claims, wherein the press is operated at a temperature of between 30°C and 150°C12. Method according to any of the previous claims, wherein the contact dryer and the press are arranged in-line, such that the dried yeast biomass is directly fed to the press, without any additional heating steps.

13. Method according to any of the previous claims, wherein the yeast biomass comprises between 20 and 70 wt.% oil on a dry matter basis.

14. Method according to any of the previous claims, wherein said yeast oil containing fraction has a solid fat content at 20°C of between 5 and 80 wt.%.

15. Method according to claim 14, wherein said yeast oil containing fraction has a solid fat content at 20°C of between 5 and 30 wt.%.

16. Method according to any of the previous claims, wherein the yeast biomass comprises an oleaginous yeast.

17. Method according to claim 16, wherein said oleaginous yeast is Cutaneotrichosporon oleaginosus .

18. Method according to any of the previous claims, the method comprising the steps of: i. drying the yeast biomass, wherein the drying is carried out in a drum dryer, wherein in the drum dryer heat is transferred to the yeast biomass primarily through direct contact with a heated surface, wherein the drying is carried out for a period between 5 and 15 seconds, ii. optionally, cooling the dried yeast biomass in a cooling apparatus, and iii. feeding the dried yeast biomass to a screw press thereby obtaining a yeast oil containing fraction, wherein the drum dryer, optionally the cooling apparatus, and the screw press are arranged in-line, such that the dried yeast biomass is directly fed to the screw press, optionally via the cooling apparatus.

19. Method of any of the previous claims, wherein the microbial biomass is dewatered by centrifugation prior to the drying step.

20. Method according to claim 19, wherein the dewatered biomass has a moisture content between 80 and 60 wt.%, preferably between 75 and 65 wt.%.