Biosynthesis of NPs CuS/Cu2S and self-assembly with C. beijerinckii for improving lignocellulosic butanol production in staged butyrate-butanol fermentation process

A staged butyrate-butanol fermentation process (SBBFP) has been developed to efficiently produce biobutanol from renewable lignocellulose. The SBBFP combines the fermentation of bioaugmented degradation consortium for butyrate (BDCB) and butanol production of Clostridium beijerinckii, but is still challenged by the lower specific butanol yield (SBY). In this study, a novel technology for synthesizing semiconductor nanoparticles (NPs) and their self-assembly with Clostridium beijerinckii was proposed to enhance the SBY. Results showed that supplement of 0.1 g/L CuSO4 or 0.2 g/L ZnSO4 were more favorable for the formation of butyrate and NPs (CuS/Cu2S or ZnS) in the acidogenic fermentation process of BDCB. Butyrate production achieved 19–21 g/L in the fed-batch fermentation mode from NaOH-pretreated rice straw. Only CuS/Cu2S can be assembled with NPs@C. beijerinckii hybrid system, and a butanol production of 14.6 g/L was obtained using acidogenic fermentation broth and saccharide liquid from rice straw as the co-substrates, with the SBY of 0.17 g/g initial pretreated rice straw. The enhanced butanol synthesis was likely attributed to the upgraded intracellular NADH/NAD+ and specific activity of enzyme CoA-transferase (ctfAB) in C. beijerinckii. The research work provides an efficient approach for biofuels and biochemical production from lignocellulose, along with the extended application of biological nanotechnology.