Submitted to: Elsevier
Publication Type: Book / Chapter
Publication Acceptance Date: 3/26/2014
Publication Date: 8/13/2014
Citation: Ezeji, T.C., Liu, S., Qureshi, N. 2014. Mixed sugar fermentation by Clostridia and metabolic engineering for butanol production. In: Qureshi, N., Hodge, D., Vertes, A., editors. Biorefineries: Integrated Biochemical Processes for Liquid Biofuels. Amsterdam, The Netherlands: Elsevier. p. 191-204.
Technical Abstract: Owing to increased awareness of fast depletion of global oil deposits and greenhouse gas emissions, concerted efforts are being made to produce alternative renewable liquid biofuels whose physical and chemical characteristics are close to that of gasoline. One such biofuel is butanol as it is less corrosive; miscible with gasoline and diesel, and its energy content is comparable to that of gasoline. Because of the solubility characteristics of butanol, it can be transported in existing fuel pipelines and tanks. One overarching factor influencing the economic viability of butanol fermentation is sustainable availability of substrates for butanol production at competitive price. In this respect, inexpensive substrate such as lignocellulosic biomass has been proposed as a viable alternative to classical substrates such as corn, starch, sucrose, and glucose. While lignocellulosic biomass represents the most abundant renewable energy resource on the planet and can be obtained on sustainable basis for the production of butanol, the material presents challenges that need to be addressed before it can be used effectively for economical fermentative production of butanol. These challenges include: a) the heterogeneous nature of lignocellulosic biomass in terms of sugar components, and b) generation of microbial inhibitory compounds during deconstruction of lignocellulosic biomass to monomeric sugars for microbial utilization. This chapter, therefore, details: (1) mixed sugar fermentations by solventogenic clostridia; (2) metabolic engineering of solventogenic clostridia to increase butanol’s titer and butanol to acetone ratio; (3) effect of microbial inhibitory compounds, derived during pretreatment process, on cell growth and butanol fermentation; and (4) future perspectives on challenges and potential strategies for overcoming bottlenecks that impede commercialization of fermentative production of butanol.