产顺,顺-粘康酸细胞工厂的构建与优化

Construction and optimization of microbial cell factories for producing cis,cis-muconic acid

顺,顺-粘康酸是重要的平台化学品。目前,生物合成顺,顺-粘康酸还缺乏高性能菌株,已报道的主要工程菌株不仅需要诱导表达,遗传不稳定,而且发酵培养基组分复杂,不利于大规模工业化生产。构建能利用简单无机盐培养基、遗传稳定且不需要诱导表达的新型工程菌受到人们的关注。本研究在实验室前期构建的产三脱氢莽草酸工程菌株WJ060中,整合合成顺,顺-粘康酸的3个外源基因(aro Z、aro Y、cat A),并且利用3个不同强度的组成型启动子进行组合调控,成功构建了27株顺,顺-粘康酸工程菌,得到的最优工程菌MA30的产量达到1.7 g/L。为了进一步提高顺,顺-粘康酸工程菌的生产能力,利用基因组复制工程构建突变体库,结合高通量筛选方法,经过两轮筛选,成功筛选到了顺,顺-粘康酸产量提高超过8%的大肠杆菌MA30-G2。利用5 L发酵罐进行分批补料发酵,MA30-G2的顺,顺-粘康酸产量达到了11.5 g/L。本研究采用组合调控和高通量筛选相结合的策略不仅促进了顺,顺-粘康酸的生物合成,同时也为其他生物基化学品的生物制造提供了重要参考。

cis, cis-muconic acid（MA） is an important platform chemical. Now, majority of reported engineered strains are genetically instable, the exogenous genes are expressed under the control of expensive inducer and the components of their fermentation medium are complex, thus large-scale microbial production of MA is limited due to the lack of suitable strains. Hence, it is still necessary to construct novel high-performance strain that is genetically stable, no induction and grows in simple inorganic fermentation medium. In this study, after 3 exogenous genes（aro Z, aro Y, cat A） for biosynthesis of MA were integrated into previously constructed 3-hydroshikimate producing Escherichia coli WJ060 strain and combinatorially regulated with 3 constitutive promoters with different strengths, 27 engineered strains were constructed. The best engineered strain, E. coli MA30 could produce 1.7 g/L MA in the simple inorganic fermentation medium without induction. To further enhance the production capacity of MA, the mutant library of E. coli MA30 was constructed by genome replication engineering and screened via high-throughput assay. After two-round screening, the new strain, E. coli MA30-G2 with improved production of MA was obtained, and the titer of MA increased more than 8%. Under the condition of 5 L fed-batch fermentation, E. coli MA30-G2 could produce about 11.5 g/L MA. Combinatorial regulation and high-throughput screening provide important reference to microbial production of other bio-based chemicals.