Lipid Production by Rhodotorula glutinis in Continuous Cultivation with a Gravity Sedimentation System

Lipid accumulation is generally believed to be a partially growth-coupled biochemical process that results in differences in lipid content between different cells. To separate lipid-rich cells and increase the cellular biomass in bioreactors during the cultivation of the oleaginous yeasts, a gravity sedimentation system (GSS) is coupled to a bioreactor. The dilution rate (D) and the ratio of the outflow rate from the outlet of the GSS to the inflow rate into the bioreactor (B) were evaluated. The biomass in the bioreactor with GSS increased by 16.3% and 30.6% at D values of 0.05 h^-1 (B = 0.25) and 0.02 h^-1 (B = 0.5), respectively. Interestingly, cells containing 39.3% lipids were obtained from the outlet of the GSS (D = 0.02 h^-1, B = 0.5), and the lipid content increased by 7.8% compared to that of the bioreactor. The results indicated that use of a GSS is a very effective method for increasing the cell concentration and separation of lipid-rich cells.