Abstract

Clostridium acetobutylicum DSM 792 has been characterized as a native acetone-butanol-ethanol (ABE) fermenting bacterium. C. acetobutylicm is used as a model organism to improve solvent production by metabolic engineering strategies. In this study, the ABE pathway in C. acetobutylicum was modified by overexpressing the pyruvate decarboxylase gene from Zymomonas mobilis under the control of 2 promoters, namely Pferr and Ppta (promoters of genes encoding pyruvate ferredoxin oxidoreductase and phosphotransacetylase) and the recombinant strains were designated as DSM 792(pPDC1) and DSM 792(pPDC2). The specific activity of the alcohol dehydrogenases in the pdc-expressing strains was higher than that in the wild-type strain. In batch fermentation experiments, the total ABE production from the recombinant strains DSM 792 (pPDC1) and DSM 792 (pPDC2) was 1.57 and 7.9 g/L, respectively, which was higher when compared to the wild type ABE production (0.64 g/L) under uncontrolled pH. The alcohol to acetone ratio (BE/A) was found to be 2.28, 2.77, and 5.26 in wild type, DSM 792 (pPDC1), and DSM 792 (pPDC2), respectively. This suggests that the re-routing of pyruvate by overexpression of the pdc could play a role in the generation of more reducing equivalents towards ethanol and butanol production.

中文翻译：

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工程化丙酮丁醇梭菌通过过度表达运动发酵单胞菌的丙酮酸脱羧酶来增强溶剂生产

摘要

丙酮丁醇梭菌DSM 792 已被表征为天然丙酮-丁醇-乙醇 (ABE) 发酵细菌。丙酮丁醇梭菌被用作模型生物以通过代谢工程策略提高溶剂产量。在这项研究中，通过在 2 个启动子 Pferr 和 Ppta（编码丙酮酸铁氧还蛋白氧化还原酶和磷酸转乙酰酶的基因的启动子）控制下过表达来自运动发酵单胞菌的丙酮酸脱羧酶基因来修饰丙酮丁醇梭菌中的 ABE 途径，并指定重组菌株如 DSM 792(pPDC1) 和 DSM 792(pPDC2)。pdc-中醇脱氢酶的比活性表达菌株高于野生型菌株。在分批发酵实验中，重组菌株 DSM 792 (pPDC1) 和 DSM 792 (pPDC2) 的 ABE 总产量分别为 1.57 和 7.9 g/L，与野生型 ABE 产量 (0.64 g/L) 相比更高) 在不受控制的 pH 值下。发现野生型、DSM 792 (pPDC1) 和 DSM 792 (pPDC2) 中的醇与丙酮比 (BE/A) 分别为 2.28、2.77 和 5.26。这表明通过pdc过表达对丙酮酸的重新路由可以在产生更多还原当量的乙醇和丁醇生产中发挥作用。