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Engineering Clostridium saccharoperbutylacetonicum for High Level Isopropanol-Butanol-Ethanol (IBE) Production from Acetic Acid Pretreated Switchgrass Using the CRISPR-Cas9 System
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2019-10-11 , DOI: 10.1021/acssuschemeng.9b05336
Pixiang Wang 1 , Jun Feng 1 , Liang Guo 2 , Oladiran Fasina 1, 3 , Yi Wang 1, 3
Affiliation  

We previously established a biomass pretreatment approach using acetic acid (which can be used as a carbon source for acetone-butanol-ethanol (ABE) fermentation) as the chemical catalyst, leading to comprehensive biomass utilization and enhanced solvent production (especially acetone production due to reassimilation of elevated fatty acids) using Clostridium saccharoperbutylacetonicum. However, acetone is corrosive to engine parts and cannot be used as a fuel. Thus, acetone produced during ABE fermentation is considered as an undesirable byproduct. In this study, we metabolically engineer C. saccharoperbutylacetonicum for isopropanol-butanol-ethanol (IBE) production by introducing secondary alcohol dehydrogenase gene to convert acetone into isopropanol. With either plasmid-based or CRISPR-Cas9-mediated chromosomal-integration-based overexpression, efficient IBE production was achieved. To further enhance solvent production, we additionally overexpressed sol operon (ald-ctfA-ctfB-adc), expression cassette EC (thl-hbd-crt-bcd) or sol in combination with EC. All resultant mutants generated elevated solvents, with one mutant produced 34.2 g/L IBE with a yield of 0.48 g/g. Finally, simultaneous saccharification and fermentation was carried out with the mutant using acetic-acid-pretreated switchgrass, and 16.2 g/L IBE was produced. Our engineered strain produced the highest IBE that has ever been reported in a batch fermentation. Our results indicated that acetic-acid-pretreated biomass can be efficiently converted into biofuel using metabolically engineered Clostridium.

中文翻译:

使用CRISPR-Cas9系统对糖化梭菌梭状芽胞杆菌进行工程化,以从醋酸预处理的柳枝Switch中高水平生产异丙醇-丁醇-乙醇(IBE)

我们之前建立了一种生物质预处理方法,该方法使用乙酸(可将其用作丙酮-丁醇-乙醇(ABE)发酵的碳源)作为化学催化剂,从而导致生物质的综合利用和溶剂产量的提高(特别是由于丙酮的产生)。糖化丁酸梭状芽孢杆菌重新同化脂肪酸)。但是,丙酮会腐蚀发动机部件,因此不能用作燃料。因此,在ABE发酵过程中产生的丙酮被认为是不希望的副产物。在这项研究中,我们通过代谢工程改造了糖蔗丁酸丙酮酸梭菌。通过引入仲醇脱氢酶基因将丙酮转化为异丙醇来生产异丙醇-丁醇-乙醇(IBE)。通过基于质粒或CRISPR-Cas9介导的染色体整合的过表达,可以实现高效的IBE生产。为了进一步提高溶剂生产,我们另外过表达的溶胶操纵子(ALD - CTFA - ctfB - ADC),表达盒EC(THL - HBD - CRT - BCD)或溶胶与EC结合使用。所有所得突变体均产生升高的溶剂,其中一个突变体产生34.2 g / L IBE,产率为0.48 g / g。最后,用乙酸预处理的柳枝with与该突变体同时进行糖化和发酵,并产生了16.2g / L IBE。我们的工程菌株产生了最高的IBE,这在分批发酵中已有报道。我们的结果表明,使用代谢工程梭菌可以将乙酸预处理的生物质有效地转化为生物燃料。
更新日期:2019-10-12
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