Determination of the optimal conditions for the continuous culture of Candida utilis in sugarcane stillage

Summary Candida utilis was continuously cultured in sugarcane stillage without any supplementation, but the yeast utilized the stillage nitrogen only partially. As a result, the cell biomass production was low and the residual chemical oxygen demand (COD), as well as the total nitrogen content of the effluent were high. The addition of 2–4 g/l ammonium phosphate and small amounts of Fe²⁺, Cu²⁺, and Zn²⁺, markedly enhanced both the everall nitrogen uptake and cell biomass production, decreased COD, and a higher critical dilution rate was attained. No substantial differences were found when pH was kept at 5.0 or allowed to evolve freely. The optimal temperature range was between 30 and 35°C.