Australian Thraustochytrids: potential production of biofuels and long-chain omega-3 oils using industrial wastes

Cultivation of heterotrophic microalgae as a feedstock for biofuels production may provide a solution to the limited availability of biomass feedstock that is expected to restrict industry uptake of transportation biofuels.... [ view full abstract ]

Cultivation of heterotrophic microalgae as a feedstock for biofuels production may provide a solution to the limited availability of biomass feedstock that is expected to restrict industry uptake of transportation biofuels. Thraustochytrids are heterotrophic protists, which are characterised by their capacity to produce omega-3 long-chain (≥C20) polyunsaturated fatty acids (ω3 LC-PUFA), including 22:6ω3 (docosahexaenoic acid, DHA). Due to their fast growth rate and high lipid content, thraustochytrids have potential for producing a feedstock for high value long-chain ω3 oils and also the shorter chain (≤C18) fatty acids suitable for biodiesel. The formation of high-value lipids during biofuel production is desirable both from a diversified product perspective and to add greater value to the production process and to improve process economics. We demonstrated the potential green house gas impact of this cultivation system using these Australian thraustochytrids for production of biodiesel with a life-cycle assessment (LCA). In addition, we examined cultivation of thraustochytrids using industrial wastes such as crude glycerol, soy pulp and protein meals, as carbon and nitrogen sources. The crude glycerol was not pre-treated prior to addition to the culture medium, with an overall aim of avoiding or minimizing unnecessary processing costs. Our initial results showed that impurities in the crude glycerol hindered growth of thraustochytrids, with a maximum yield of 9 g/L dry cell weight and 48% DHA of total fatty acids achieved at 4-days under the shake-flask conditions used. Heterotrophic cultivation of thraustochytrids in industrial wastes offers considerable potential for commercial production of biofuels and other high-value lipids, with future efforts needing to enhance biomass yield.