Abstract
Microorganisms are known to be natural oil producers in their cellular compartments. Microorganisms that accumulate more than 20% w/w of lipids on a cell dry weight basis are considered as oleaginous microorganisms. These are capable of synthesizing vast majority of fatty acids from short hydrocarbonated chain (C6) to long hydrocarbonated chain (C36), which may be saturated (SFA), monounsaturated (MUFA), or polyunsaturated fatty acids (PUFA), depending on the presence and number of double bonds in hydrocarbonated chains. Depending on the fatty acid profile, the oils obtained from oleaginous microorganisms are utilized as feedstock for either biodiesel production or as nutraceuticals. Mainly microalgae, bacteria, and yeasts are involved in the production of biodiesel, whereas thraustochytrids, fungi, and some of the microalgae are well known to be producers of very long-chain PUFA (omega-3 fatty acids). In this review article, the type of oleaginous microorganisms and their expertise in the field of biodiesel or omega-3 fatty acids, advances in metabolic engineering tools for enhanced lipid accumulation, upstream and downstream processing of lipids, including purification of biodiesel and concentration of omega-3 fatty acids are reviewed.
Highlights
The world’s energy threats have already appeared as a consequence of rapid population growth, extremely unbalanced supplies of food, diminished stockpiles of petroleum resources, and reduced natural resources [1]
It contains a high amount of free fatty acids (FFA), which severely affect the age of oils in terms of oxidative stability [12]
Microbial oils have several advantages such as productivity is usually higher than the plants or vegetable oils, easier upstream and downstream processing, easy genetic modifications for the specific products, and they can grow in a controlled environment without being dependent on the climate [14,15]
Summary
The world’s energy threats have already appeared as a consequence of rapid population growth, extremely unbalanced supplies of food, diminished stockpiles of petroleum resources, and reduced natural resources [1]. Vegetable oils can be considered as an alternative source of only linoleic (C18:2 n−6, LA), ALA and arachidonic acid (C20:4 n-6, AA) but the large chain PUFA such as DHA and EPA are unable to be synthesize by plants due to lack of elongases and desaturases [32]. Some engineered plants such as Brassica juncea, Arabidopsis thaMliiacnroao,rgaannidsmCs a2m02e0l,i8n,ax sFaOtRivPaEaErReRgEoVoIEdWsources for LC-PUFA; utilization of these transgen iocf 39 crops is under consideration of regulatory authorities and social rivalry [33]. Oleaginous microorganisms involved in the production of biofuels and nutraceuticals aMreicrdoiosrgcaunsissmesd2.02A0,n8,ixllFuOsRtrPaEtiEvReRdEViaIgEWram is presented to show the advantage of using biodiesel4aonfd omega-3 fatty acids from microbial oil to combat the problem associated with the utilization of cboinovdeinestieolnaanlddioesmelegfuae-3l afnadttyomaceigdas-3frfoamttymacicidrosbfriaolmofiilsthoocilosm(Fbiagtutrhee2)p. roblem associated with the utilization of conventional diesel fuel and omega-3 fatty acids from fish oils (Figure 2)
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