Comparison of batch and fed-batch fermentations using corncob hydrolysate for bioethanol production

Abstract

The optimal conditions for the maximum production of ethanol from cellulosic hydrolysate in batch and fed-batch cultures were investigated and compared. The pretreated corncob could be converted into reducing sugar with maximal yields after the enzyme mixtures were fed. After 48h of hydrolytic reaction, overall reducing sugar and glucose concentrations reached 0.61 and 0.36g/g dried substrate, respectively. Further batch fermentation of cellulosic hydrolysate was performed using batch cultures of Saccharomyces cerevisiae BCRC 21812, 23.3–41.1g/l biomass and 6.9–23.0g/l ethanol was obtained. For the fed-batch fermentation, the effects of feeding glucose concentrations on ethanol fermentation were studied. The feeding glucose concentration of 30g/l resulted in a higher ethanol yield than that of 20g/l and 10g/ldid. The cell biomass, ethanol yields, and ethanol conversion rate for the fed-batch fermentation, feeding at 30g/l glucose concentration, were 44.5g/l, 32.3g/l and 0.64g ethanol/g glucose, respectively. The results indicate that the fed-batch fermentation had a higher ethanol yield than that of the batch fermentation.