Clostridium species for alcohol production: insights into genetic, metabolic and bioprocess engineering approaches

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Numerous anaerobic bacteria that metabolize various substrates are members of the Clostridium genus. Their unique biphasic fermentative metabolism is vital to the required anaerobic fermentation process. Clostridium sp. vegetative cells produce acetic and butyric acids during the exponential growth phase, also known as the acidogenesis phase. The solventogenic transition in the fermentation of acetone, butanol, and ethanol (ABE) happens when the cells’ metabolism changes to solvent synthesis, also known as solventogenesis. Clostridium has the potential to utilize a wide variety of substrates to make different types of alcohols. Still, researchers have encountered certain drawbacks in large-scale fermentative production in the past few decades. There are numerous species in the Clostridium genus. Still, only a few are industrially applicable due to challenges such as inhibitory effects from lignocellulosic biomass, product inhibition, and difficulty in genetic manipulation. Also, much research still needs to be done on changing metabolic pathways and the processes that come after. Clostridium can be a beneficial alternative host to other bacterial and yeast-derived alcohol productions by addressing the abovementioned drawbacks. This review has depicted some genetic, metabolic, and bioprocess engineering strategies to decipher certain obstacles and develop Clostridium as one of the best choices for industrial alcohol production.