Lipid production by Rhodosporidium toruloides Y2 in bioethanol wastewater and evaluation of biomass energetic yield

The oleaginous yeast Rhodosporidium toruloides Y2 was employed to remove waste nutrients from bioethanol wastewater while simultaneously producing biomass enriched in microbial lipids. Under optimal conditions, the COD degradation ratio, biomass and lipid content reached 72.3%, 3.8 g/l and 34.9%, respectively. For accelerating biomass and lipid accumulation, different feeding strategies of substrate were conducted. The biomass and lipid production increased by 39.5% and 53.8%, respectively, when glucose at 1.2 g/(l d) was added during the last three days of the cultivation. An equation was established to estimate biomass energetic yield. Under optimal conditions, the biomass energetic yield was 50.9% and an increase of 26.0% was obtained by feeding glucose at 1.2 g/(l d) during the last three days. The fatty acid composition of the lipids was similar to that from plant oils and other microbial lipids, and could thus be used as raw material for feed additives and biodiesel production.