The microbial production of 1-butanol utilizes various species of Clostridium, p

Question

The microbial production of 1-butanol utilizes various species of Clostridium, particularly acetobutylicum. Clostridium acetobutylicum is a Gram-positive anaerobe which also produces byproducts such as butyrate, acetone, and ethanol. As a result, its 1-butanol yield is difficult to control. Its relatively slow growth rate and spore-forming life cycle create additional problems for industrial fermentation. Furthermore, the relatively unknown genetic system and complex physiology of the microorganism present difficulties in engineering its metabolism for optimal production of 1-butanol. Therefore, there is strong incentive to produce 1-butanol from a user-friendly organism. In this regard, Escherichia coli is a well-characterized microorganism with a set of readily available tools for genetic manipulation and its physiological regulation is well-studied. E. coli has previously been shown to be a suitable host for the production of valuable metabolites.

Propose your strategies (at least more than three) to improve 1-butanol production in Escherichia coli and explain the reason.

Explanation / Answer

1. There was a pta deletion which caused undesirable accumulation of pyruvate,butanoate etc.The reduction of butanoyl CoA to butnal can be catalyzed by alcohol dehydrogenase Adh E2. This is a rate limiting step.AdhE2 can be enhanced .This can direct more 1 butanol production and reduce the production of undesirable products like pyruvate and butanoate.Thus by resolving CoA imbalance this problem can be solved.

2.Membrane targeted tilapia metallothionenin and the clostridial metabolic pathway in E.coli can be used together for their coexpression for n butanol production.

3.The Ompc-TMT in E.Coli engineered strain improved n butanal productivity to significant amount . Thus Ompc- TMT can increase n butanol production by scavenging ROS.

4.1 Butanol productivity was directly correlated with Fdh activity switching cells to oxygen limiting conditions prior to significant accumulation of biomass appeared to be important for the induction of enzyme synthesis and the efficiency of 1 butanol can be possible anaerobically under high density fermentation.

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