Towards sequential bioethanol and L-lactic acid co-generation: Improving xylose conversion to L-lactic acid in presence of lignocellulosic ethanol with an evolved Bacillus coagulans

摘要

A wide range of biofuels and bio-based products can be produced from lignocellulose considering its high compositional diversity. Ethanol production by yeasts from cellulosic glucose is well-known, while hemicellulosic xylose utilization is still challenging. This work proposes the use the xylose for L-lactic acid fermentation. In this context, a sequential cultivation of Saccharomyces cerevisiae and the C5-utilizing Bacillus coagulans is studied. High ethanol yields, around 0.44 g g(-1), were obtained from a cellulosic-gardening hydrolysate. The high ethanol concentrations did not affect the evolved B. coagulans A20-EXA obtained by adaptive evolution to ethanol. As a result, 2.6-fold increase in lactic acid yield was achieved when compared with parental B. coagulans strain in presence of 5% (v v(-1)) ethanol. These results demonstrated the suitability of B. coagulans A20-EXA to be used together with S. cerevisiae for the sequential co-generation of ethanol and lactic acid from lignocellulosic biomass in a biorefinery approach. (C) 2020 Elsevier Ltd. All rights reserved.