Enhanced biobutanol production using novel clostridial fusants in simultaneous saccharification and fermentation of green renewable agriculture residues

Abstract

AbstractThermostable Clostridia species were developed in the present study through protoplast fusion between mesophilic and thermophilic clostridial species. Two parental strains of Clostridia species, Clostridium acetobutylicum (ATCC 4259) and Clostridium beijerinckii (ATCC BA101), along with three fused strains, Clostridium acetobutylicum Clostridium thermocellum (CaCt), Clostridium beijerinckii Clostridium thermocellum (CbCt) and Clostridium acetobutylicum Clostridium beijerinckii (CaCb), were examined for biobutanol production using wheat straw (WS) as a feedstock in a batch process of simultaneous saccharification and fermentation (SSF). The objective of the study was to use the thermotolerant fused strains to enhance enzymatic activity during the SSF by raising the incubation temperature and thereby eventually increasing biobutanol production. Results from the current study indicated that the fused strains were able to produce the required enzymes at higher temperature essential for the saccharification of WS (i.e., endoglucanase, exoglucanase, and β‐glucosidase). This will have a major impact on eliminating costs associated with adding enzymes to the saccharification process. Fused strain CbCt achieved the highest biobutanol production of up to 14.13 g/L (i.e., a yield of 0.29) at 45 °C with total sugar consumption of 82%. Enzymatic activity of CbCt was found to be 61.67 FPU (filter paper unit) which was the highest in comparison with other fused strains evaluated in this study. These results indicate a breakthrough for the technological and economical obstacles associated with industrialization of the SSF process. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd