Oils from Microorganisms

Abstract

All microorganisms, bacteria, yeasts, fungi, and algae, produce lipids. The range of fatty acids that can be sourced from the lipids produced by the microbial world is vast. Some microbial species (described as oleaginous species) produce large amounts – sometimes up to 70% of the cell mass – of triacylglycerol oils, which can be produced in large volumes, be extracted and processed using techniques similar to those used for conventional and commercially produced plant seed oils. These microbial products are known as the single cell oils (SCO). They have, on occasion, been considered as alternative sources to plant‐based oils. However, because of the high costs of fermentation technology needed to cultivate these microorganisms at a large scale, replacing commodity plant oils with SCO is uneconomical in the foreseeable future and only the highest valued microbial oils can be considered commercially viable. This article gives a brief background to microbial technology and gives examples of how SCOs were pioneered, as sources of gamma‐linolenic acid, as alternatives to evening primrose oil and borage oil, and for the production of cocoa butter equivalent oils for use in chocolate confectionery. Current commercial productions of arachidonic acid (20:4, n −6) using the filamentous fungus, Mortierella alpina , and of docosahexaenoic acid (DHA; 22:6, n −3) by the marine dinoflagellate, Crypthecodinium cohnii , and by various chytrids, for example Schizochytrium spp., are described. The potential future microbial lipid production of oil rich in eicosapentaenoic acid (EPA; 20:5, n −3) using a photosynthetic microalga, Nannochloropsis spp., is also described. The article also covers the current developments for the production of EPA + DHA as facsimile fish oils and also for the production of SCO or oil‐rich microbial biomass to support the continued expansion of the aquaculture industry. The article also gives a brief discussion of the economic impossibility of using microorganisms, whether phototrophs or heterotrophs, for the production of biodiesel.

The utility of algae as sources of high value nutritional ingredients, particularly for alternative/complementary proteins to improve human health

“…Besides saccharides, lipids serve as energy stores as well as structural components in algae. Macroalgae typically contain less than 5% lipids, while some microalgae species contain 20 to 50% lipids ( 94 , 95 ). The long-chain polyunsaturated fatty acids (PUFAs) found in algae hold particularly promising applications in nutraceuticals and pharmaceuticals as supplements, but their bioaccessibility might be limited by algal cell walls ( 96 ).…”

Rhodococcus as Biofactories for Microbial Oil Production

“…Unlike eukaryotic oil-producers, rhodococci are not able to produce TAG containing long chain-length or polyunsaturated (PUFA) fatty acids, which can be used mainly for nutritional and pharmaceutical applications. Long polyunsaturated fatty acids, i.e., docosahexaenoic acid (22:6, ω-3) and arachidonic acid (20:4, ω-6), are produced by oleaginous fungi such as Mortierella alpine or Mucor circinelloides and different oleaginous microalgae ( Table 1 ) [ 1 ]. However, different engineering strategies have been suggested for rhodococci to modify the composition of the accumulated TAG to expand their field of application.…”

“…Some eukaryotic microorganisms, such as fungi, microalgae, and yeasts, can be considered oleaginous species because they are able to produce more than 20% (of cellular dry weight, CDW) of triacylglycerols (TAG) [ 1 ]. They exhibit some differential metabolic features compared to non-oleaginous related species, such as a high flux of acetyl-CoA and NADPH to fatty acid and TAG biosynthetic pathways during the cultivation of cells under nitrogen-limiting conditions in the presence of an excess of the carbon source [ 2 ].…”

Energy-Efficient Production of Microchloropsis salina Biomass with High CO2 Fixation Yield in Open Thin-Layer Cascade Photobioreactors

“…Still, microalgae processes remain uncompetitive for the production of low-value-added products due to the high production costs associated with their low lipid space-time yield [1]. Hence, the current application areas of microalgae remain limited to mainly wastewater treatment [2,3]; aquaculture supplying foodstuffs [4,5]; and the production of specific polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid, eicosapentaenoic acid, or arachidonic acid, for use as nutraceuticals [6].…”

“…One of the main challenges of microalgae cultivation in open PBRs is, alongside productivity issues, the heightened risk of contamination [6]. Thus, to reduce this risk, it is essential to cultivate microalgae strains that thrive in extreme conditions, which are unfavorable for potential contaminants.…”