5-羟基戊酸(5-hydroxyvaleric acid,5-HV)是一种重要的五碳化合物,在医药、香料、材料等领域具有广泛应用。目前生物法合成5-HV的研究较少,其大多是作为中间体被发现,且存在产量低、成本高等问题。该研究对实验室一株产5-HV的大肠杆菌进行改造,通过去除质粒中的乳糖操纵子的部分元件,构建了无需诱导即能合成5-HV的菌株,从而避免了使用昂贵的、有毒性的诱导剂IPTG。随后,通过过表达限速酶(醛还原酶)的转录激活子yqhC,提高了5-HV的产量。为了减少发酵过程中的碱用量,将Hfq-DsrA抗酸元件引入底盘细胞,提高了菌株的酸耐受能力。最终,在10 L发酵罐水平上,维持发酵液的pH为酸性环境,构建的代谢工程菌株的5-HV滴度达到47.5 g/L,糖酸的质量转化率为42%,碱液使用量减少了45%。该研究方法和结果对于生物法5-HV的规模化生产具有积极的指导意义。
5-Hydroxyvaleric acid (5-HV) is an important five-carbon compound with a wide range of applications in the fields of pharmaceuticals, fragrances, and materials.At present, there are few studies on the biological production of 5-HV, which is mostly discovered as an intermediate and suffers from low yield and high production cost.In this study, a 5-HV-producing E.coli strain from our laboratory was modified to synthesize 5-HV without induction by removing some elements of the lactose manipulator in the plasmid, thus avoiding the use of the costly and toxic inducer IPTG.The 5-HV titer was further improved by overexpressing the transcriptional activator of the rate-limiting enzyme aldehyde reductase, yqhC.To reduce the amount of base used during fermentation, the Hfq-DsrA antacid element was introduced into the chassis cells to improve the acid tolerance of the strain.Finally, in a 10 L fermenter, the pH of the fermentation broth was maintained in an acidic environment, and 47.5 g/L of 5-HV was achieved with a yield of 42% (glucose to 5-HV, mass fraction), while the amount of alkali added was reduced by 45%.The methodology and results of this study are instructive for the large-scale bioproduction of 5-HV.
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