Using cell recycling batch fermentations to validate a setup for cellulosic ethanol production.

BACKGROUND Although cells recycling has been recognized as an important technology in obtaining first generation ethanol, there are few studies using this technology to obtain second generation ethanol, limited only to the fermentation of lignocellulosic hydrolysate and molasses mixture. The present work evaluated the use of cell recycle batch fermentation to validate a setup for cellulosic ethanol production. Setup considered a diluted phosphoric acid pretreatment followed by alkaline delignification, enzymatic hydrolysis, hexoses concentration, and finally, cell recycle batch fermentations. After the concentration step of cellulosic hydrolysate, performance of Saccharomyces cerevisiae recycling was evaluated from parameters related to the alcoholic fermentation, such as productivity and ethanol yield. RESULTS Global productivity values of 1.94, 4.19, 5.62, 5.68 and 5.81 g L−1 h−1 were obtained for all batch fermentations, respectively. Fermentation reaction was performed for 8 h in the 3rd, 4th and 5th batches. The medium yield of 87.4% and ethanol titer of 47.0 g L−1 were obtained in nearly all batches. CONCLUSIONS The results showed good performance of the yeast with consumption of almost all glucose present in cellulosic hydrolysate without sterilization and supplied with molasses. In this context, the setup proposed can be a possible design for second generation ethanol production. © 2015 Society of Chemical Industry