Yeast single cell oil (SCO) is a non-crop-based, renewable oil source that can be used for the production of bio-based oleochemicals. Stand-alone production of SCO for oleochemicals is currently not cost-competitive because lower-cost alternatives from petroleum and crop-based resources are available. Utilizing low-valued nutrient sources, implementing cost-efficient downstream processes and adopting biotechnological advancements such as systems biology and metabolic engineering could prove valuable in making an SCO platform a reality in the emerging bio-based economy. This review aims to consider key biochemical pathways for storage lipid synthesis, possible pathways for SCO yield improvement, previously used bioprocessing techniques for SCO production, challenges in SCO commercialization and advantages of adopting a renewable SCO platform.
Enzymatic reactions in non-aqueous media have been shown to be effective in carrying out chemical transformation where the reactants are insoluble in water or water is a byproduct limiting conversion. Ionic liquids, liquid organic salts with infinitesimal vapor pressure, are potentially useful alternatives to organic solvents. It is known that the thermodynamic water activity is an important variable affecting the activity of enzymes in non-aqueous solvents. This study investigated the influence of water activity on the esterification of geraniol with acetic acid in ionic liquid [bmim]PF6 catalyzed by immobilized Candida antarctica lipase B. The conversion of geraniol in [bmim]PF6 was significant although the reaction rate was slower than in organic solvents. The profile of initial reaction rate-water activity was determined experimentally, and differed from the data reported for other non-aqueous solvents. A maximum in the initial reaction rate was found at aw = 0.6. The pseudo reaction equilibrium constant, Kx, was measured experimentally for the reaction. The average value of Kx in [bmim]PF6 was 12, 20-fold lower than the value reported for the same system in hexane.
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