Zhang Zheng, He Penghui, Hu Shiying, Yu Yanqing, Wang Xiaoting, Ishaq Ali Raza, Chen Shouwen
State Key Laboratory of Biocatalysis and Enzyme Engineering, Environmental Microbial Technology Center of Hubei Province, College of Life Sciences, Hubei University, 430062, Wuhan, China.
, 368 Youyi Avenue, Wuchang District, 430062, Wuhan, Hubei, PR China.
World J Microbiol Biotechnol. 2023 Mar 15;39(5):115. doi: 10.1007/s11274-023-03560-0.
Metabolic engineering is a substantial approach for escalating the production of biochemical products. Cell biomass is lowered by system constraints and toxication carried on by the aggregation of metabolites that serve as inhibitors of product synthesis. In order to increase the production of biochemical products, it is important to trace the relationship between alanine metabolism and biomass. According to our investigation, the appropriate concentration of additional L/D-alanine (0.1 g/L) raised the cell biomass (OD) in Bacillus licheniformis in contrast to the control strain. Remarkably, it was also determined that high levels of intracellular L/D-alanine and D-alanyl-D-alanine were induced by the overexpression of the ald, dal, and ddl genes to accelerate cell proliferation. Our findings clearly revealed that 0.2 g/L of L-alanine and D-alanine substantially elevated the titer of poly-γ-glutamic acid (γ-PGA) by 14.89% and 6.19%, correspondingly. And the levels of γ-PGA titer were hastened by the overexpression of the ald, dal, and ddl genes by 19.72%, 15.91%, and 16.64%, respectively. Furthermore, overexpression of ald, dal, and ddl genes decreased the by-products (acetoin, 2,3-butanediol, acetic acid and lactic acid) formation by about 14.10%, 8.77%, and 8.84% for augmenting the γ-PGA production. Our results also demonstrated that overexpression of ald gene amplified the production of lichenysin, pulcherrimin and nattokinase by about 18.71%, 19.82% and 21.49%, respectively. This work delineated the importance of the L/D-alanine and D-alanyl-D-alanine synthesis to the cell growth and the high production of bio-products, and provided an effective strategy for producing bio-products.
代谢工程是提高生化产品产量的重要方法。细胞生物质会因系统限制以及作为产物合成抑制剂的代谢物聚集所导致的中毒现象而减少。为了提高生化产品的产量，追踪丙氨酸代谢与生物质之间的关系很重要。根据我们的研究，与对照菌株相比，添加适量的L/D-丙氨酸（0.1 g/L）可提高地衣芽孢杆菌的细胞生物质（OD值）。值得注意的是，还确定了通过ald、dal和ddl基因的过表达诱导高水平的细胞内L/D-丙氨酸和D-丙氨酰-D-丙氨酸，以加速细胞增殖。我们的研究结果清楚地表明，0.2 g/L的L-丙氨酸和D-丙氨酸分别使聚-γ-谷氨酸（γ-PGA）的产量显著提高了14.89%和6.19%。并且ald、dal和ddl基因的过表达分别使γ-PGA产量提高了19.72%、15.91%和16.64%。此外，为了提高γ-PGA的产量，ald、dal和ddl基因的过表达分别使副产物（乙偶姻、2,3-丁二醇、乙酸和乳酸）的形成减少了约14.10%、8.77%和8.84%。我们的结果还表明，ald基因的过表达分别使地衣素、嗜铁素和纳豆激酶的产量提高了约18.71%、19.82%和21.49%。这项工作阐明了L/D-丙氨酸和D-丙氨酰-D-丙氨酸合成对细胞生长和生物产品高产的重要性，并为生产生物产品提供了一种有效策略。
