Growth kinetics ofSaccharomyces cerevisiae in batch and fedbatch cultivation using sugarcane molasses and glucose syrup from cassava starch

Abstract

Growth kinetics ofSaccharomyces cerevisiae in glucose syrup from cassava starch and sugarcane molasses were studied using batch and fed-batch cultivation. The optimum temperature and pH required for growth were 30°C and pH 5.5, respectively. In batch culture the productivity and overall cell yield were 0.31 g L⁻¹ h⁻¹ and 0.23 g cells g⁻¹ sugar, respectively, on glucose syrup and 0.22 g L⁻¹ h⁻¹ and 0.18 g cells g⁻¹ sugar, respectively, on molasses. In fed-batch cultivation, a productivity of 3.12 g L⁻¹ h⁻¹ and an overall cell yield of 0.52 g cells g⁻¹ sugar in glucose syrup cultivation and a productivity of 2.33 g L⁻¹ h⁻¹ and an overall cell yield of 0.46 g cells g⁻¹ sugar were achieved in molasses cultivation by controlling the reducing sugar concentration at its optimum level obtained from the fermentation model. By using an on-line ethanol sensor combined with a porous Teflon^® tubing method in automating the feeding of substrate in the fed-batch culture, a productivity of 2.15 g L⁻¹ h⁻¹ with a yield of 0.47 g cells g⁻¹ sugar was achieved using glucose syrup as substrate when ethanol concentration was kept at a constant level by automatic control.