A multi-coproduct model to capture value from yeast cellular biomass: A case study from an oleaginous yeast, Rhodosporidium babjevae

Microbial bioproducts are sustainable, renewable alternatives to traditional products derived from plant, animal or petroleum sources. Production of a single high-value product from a microbial culture may be economically feasible, but this model is not realistic for commodity products such as biodiesel. We envision a microbial production model analogous to current production of multiple co-products from plant oilseeds such as soy. A portfolio of products from a single microbial culture such as oleaginous (high lipid) yeasts could improve the economics of the production process. Furthermore, several carbon sources and types of waste streams may be useful as a source of nutrients. To test these concepts, we used Rhodosporidium babjevae UCDFST 04-877, a pink, oleaginous Basidiomycete yeast from the Phaff Yeast Culture Collection, to obtain multiple products at bench scale. The yeast was cultured on lignocellulosic hydrolysate and different carbon sources. Production of intracellular lipids (triacylglycerols, TAGs), carotenoids, protein, vitamins, and extracellular glycolipids was examined. The TAGs constituted 50% of the cell biomass by dry weight, and are rich in monounsaturated fatty acids, about 60% oleic acid, which have ideal properties for biodiesel or cooking oil. Two bands associated with carotenoids were detected by TLC. In addition, up to 4g/L secreted glycolipids were obtained.  Yeast protein is a nutritious alternative to traditional plant or animal protein, for use in food or feed.  Overall, this work presents a new strategy towards a framework consisting of multiple high value products from yeast, which may lead to an economically favorable and sustainable technological platform.