Optimization of metabolic pathways for bioconversion of lignocellulose to ethanol through genetic engineering
Optimization of metabolic pathways has seen intense research interest, and is still of fundamental significance among strategies to improve economics and increase yield of lignocellulose -to-ethanol processes. Generally, no microorganisms are known to possess native pathways to ferment both hexoses (such as glucose) and pentoses (such as xylose) in an efficient manner. Although Escherichia coli is capable of actively metabolizing a wide variety of substrates, including hexoses, pentoses, lactose, etc., its hexose metabolism is inferior to that of Zymomonas mobilis, an obligately ethanologenic bacterium. The genes encoding essential enzymes of the fermentative pathway for ethanol production in Z. Mobilis were inserted into E. Coli TOP10. Alcohol dehydrogenase Ⅱ (adh Ⅱ) and pyruvate decarboxylase (pdc) from Z. Mobilis were expressed at high levels in E. Coli TOP 10 under the control of a lac promoter of pUC18 vector, resulting in increased cell growth and ethanol production. Ethanol concentrations of more than 30g/liter were obtained on 10％ glucose. Variations of the E. Coli strains constructed in this research have proved to be useful both for the production of ethanol from underutilized sources of biomass, such as hemicellulose (xylose, arabinose, etc.), which represents a major portion of wood and inedible plant parts, and whey (lactose), as well as from other biomass sources. Furthermore, since pyruvate is mainly assimilated through pyruvate formate lyase (PFL) and forms formic acid and acetyl coenzyme A (AcCoA), attempts have been made through metabolic redirection employing gene knockout strategy to decrease the byproducts of pyruvate metabolism. The effect of gene knockout by Red recombinantion on metabolism in the pflA-(pyruvate formate lyase A), pflB-(pyruvate formate lyase B) mutants of E. Coli TOP10 was investigated. It was found that pflA-and pflB-mutants produced more ethanol from glucose under the microaerobic condition, the yield being 163％ and 207％ as compared with that of the parent strain using glucose as a carbon source.
lignocellulose ethanol gene engineering knockout mutant
CHEN Jienan ZHANGWeitao TAN Li WANG Yiqiang HE Gang
Central South University of Forestry and Technology,Changsha 410004,China
国际会议
广州
英文
27-36
2008-12-03（万方平台首次上网日期，不代表论文的发表时间）