Lipid production with Trichosporon oleaginosus in a membrane bioreactor using microalgae hydrolysate

Lipid production by Trichosporon oleaginosus was first studied in fed-batch operated stirred-tank bioreactors on a milliliter- and liter-scale making use of typical sugar monomers and a sugar mixture that may be derived from microalgae biomass hydrolysis after the extraction of lipids. 20.3 g L⁻¹ lipids (58% of dry cell mass) were produced with T. oleaginosus in a defined medium at nitrogen starvation in the fed-batch process with a typical microalgae derived carbohydrate mixture (60% glucose, 20% mannose, 20% galactose). Real microalgae hydrolysate resulted in superior growth of T. oleaginosus but no enhanced lipid formation was possible due to nitrogen and phosphorus excess in the hydrolysate. Phosphate precipitation and the application of a continuously operated membrane bioreactor with total cell retention due to the low sugar concentrations (∼40 g L⁻¹) in the microalgae hydrolysate resulted in the production of 30 g L⁻¹ lipids (53% of dry cell mass) with T. oleaginosus at high space-time-yields of 0.33 g lipids L⁻¹ h⁻¹. A high apparent lipid yield of 0.43 g lipids g⁻¹ sugars consumed (130% of the theoretical maximum) was achieved with the microalgae hydrolysate most likely due to the additional conversion of other carbon sources (e.g. uronic acids, peptides) in the hydrolysate.