Problems with the microbial production of butanol

Abstract

With the incessant fluctuations in oil prices and increasing stress from environmental pollution, renewed attention is being paid to the microbial production of biofuels from renewable sources. As a gasoline substitute, butanol has advantages over traditional fuel ethanol in terms of energy density and hygroscopicity. A variety of cheap substrates have been successfully applied in the production of biobutanol, highlighting the commercial potential of biobutanol development. In this review, in order to better understand the process of acetone-butanol-ethanol production, traditional clostridia fermentation is discussed. Sporulation is probably induced by solvent formation, and the molecular mechanism leading to the initiation of sporulation and solventogenesis is also investigated. Different strategies are employed in the metabolic engineering of clostridia that aim to enhancing solvent production, improve selectivity for butanol production, and increase the tolerance of clostridia to solvents. However, it will be hard to make breakthroughs in the metabolic engineering of clostridia for butanol production without gaining a deeper understanding of the genetic background of clostridia and developing more efficient genetic tools for clostridia. Therefore, increasing attention has been paid to the metabolic engineering of E. coli for butanol production. The importation and expression of a non-clostridial butanol-producing pathway in E. coli is probably the most promising strategy for butanol biosynthesis. Due to the lower butanol titers in the fermentation broth, simultaneous fermentation and product removal techniques have been developed to reduce the cost of butanol recovery. Gas stripping is the best technique for butanol recovery found so far.

Production of Biofuels from Cellulose of Woody Biomass

“…In the literature, the simultaneous production and the removal of butanol was carried out in order to maintain a low butanol concentration in the fermentation medium (broth) using liquid-liquid extraction, adsorption, perstraction, reverse osmosis, pre-evaporation and gas stripping [89], among which gas stripping has received great attentions. Gas stripping offers several advantages including feasibility and simplicity of the process, reduction in butanol concentration without affecting culture, concentration of nutrients and reaction intermediates [86].…”

Can Microbially Derived Advanced Biofuels Ever Compete with Conventional Bioethanol? A Critical Review

“…Finally, the status of commercialization of some of the advanced biofuels compared to bioethanol, potential research avenues, and the future perspectives for their commercial success are discussed. In ABE/IBE fermentation, after glycolysis, pyruvate is converted to acetyl-CoA by the enzyme pyruvate ferredoxin oxidoreductases (Ezeji et al 2007;Fischer et al 2008;Zheng et al 2009;Jang et al 2012). Subsequently, two acetyl-CoA molecules undergo Claisen condensation to form acetoacetyl-CoA, which is reduced to 3-hydroxybutyryl-CoA, then dehydrated to form crotonyl-CoA and further reduced to butyryl-CoA, butyraldehyde, and finally butanol ( Fig.…”

Fermentable sugars and microbial inhibitors formation from two-stage pretreatment of corn stalk with variation in particle size and severity factor

“…Over the years, several pretreatment processes such as the physical (milling and grinding), the chemical (hydrothermal, high pressure steam explosion, acid, alkali, oxidizing agents, and organic solvents, ammonia fiber explosion), the biological (fungi, actinomycetes, and bacteria) as well as a combination of those pretreatment approaches have been investigated on variety of feedstocks (Taherzadeh and Karimi 2007;Zheng et al, 2009a;Kumar et al, 2009;Zheng et al, 2009b;Yang et al, 2013). Among them, chemical pretreatment process is popular, while most researchers did not emphasize physical pretreatment due to the high cost and low sugar yield and biological pretreatment due to time intensive.…”