Development of dissolved carbon dioxide‐driven‐and‐controlled repeated batch fermentation process for ethanol production

Abstract

We previously observed that as glucose is completely exhausted during ethanol fermentation, the dissolved carbon dioxide (DCO 2) level in the fermenter will suddenly decline. This observation was implemented to design and develop a DCO 2-driven-and-controlled repeated batch fermentation process for ethanol production. The process was tested at four different glucose concentrations (~150 g/L, 200 g/L,~250 g/L, and~300 g/L), and each glucose concentration was controlled under three respective DCO 2 control levels (without DCO 2 control, and DCO 2 controlled at either 1000 mg/L or 750 mg/L). The results show that reported process features complete glucose utilization and is self-driven. For glucose concentration less than 200 g/L,~41%-50% of fermentation time per batch was saved during the repeated batch operation. It took 12.1 ± 1.1 hours-14.9 ± 1.9 hours to complete a batch with glucose feed at~250 g/L and 21.7 ± 6 hours-31.5 ± 7 hours to complete a batch with glucose feed at~300 g/L. The reported process is time saving and stable, but the ethanol yield is~20% lower than the operation without DCO 2 control. Dissolved CO 2 control became essential for glucose concentrations greater than 250 g/L if zero glucose discharge in each batch during the operation is desired.