Biofuels and Bioenergy

Abstract

Acetone–butanol (AB) fermentation was initiated from the beginning of the twentieth century. The acetone or butanol produced from AB fermentation has played an important role for the artificial synthesis of rubber, the production of lacquer for mobile industry, and the manufacture of cordite during World Wars I and II. In the latter half of the twentieth century, AB fermentation declined because of its weak economic competitiveness compared with the products obtained from the developing petroleum industry. However, the unsustainability and crisis of petroleum still motivate scientists to maintain an interest on the AB fermentation for producing alternative products from biomass. Butanol, with the advantages over ethanol, such as higher energy content, lower water absorption, better blending ability, and direct use in conventional combustion engines, has been recognized as an attractive biofuel for the bioenergy system of the future, which results in the rebloom of the AB fermentation in current times. However, the butanol toxicity and cost of substrates are still the main obstacles to making AB fermentation economically feasible. Now, the genome sequences of two typical solventogenic bacteria, Clostridium acetobutylicum ATCC 824 and C. beijerinckii NCIMB 8052, have been released. The systematic analyses of solventogenic bacteria using omic technologies make it possible to obtain an insight into the physiology and metabolism, which, in conjunction with the efficient genetic tools for modification, would make the AB fermentation feasible for supplying biobutanol in bulk as fuel. This article introduces the basic knowledge about the AB fermentation and summarizes the current progress.