7 Microbial production of acetone and butanol

This chapter focuses on the microbial production of acetone and butanol. These sugars form an excellent substrate for acetone-butanol fermentation. In acetone-butanol fermentation, the bacterial strains mostly involved are different species of Clostridium. The genus is divided into five groups containing altogether 61 reference strains. Solvent producing clostridia can be found in any of the five groups. Being chemoorganotrophs, they metabolize sugars, polyalcohols, amino acids, organic acids, purines, and other organic compounds under strict anaerobic conditions. Anaerobic production of acetone-butanol was the first large scale microbial process in which the exclusion of other microbes from the culture vessel became a factor of major importance for the success of operation. To develop an economically viable acetone-butanol fermentation process, a number of points are required to be considered: (1) Any fermentation process will have to compete with the existing petroleum based process. (2) Utilization of a fully integrated plant using the most inexpensive raw materials, such as waste lignocellulosic materials. (3) Strains with improved product tolerance will be required. (4) At present, solvent production from pentoses is low as compared to glucose. Simultaneous efficient utilization of both sugars will have a major impact on process economy.