Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; Science Center for Future Foods, Jiangnan University, Wuxi 214122, China.
Department of Bioengineering and Centre for Synthetic Biology, Imperial College London, London SW7 2AZ, UK.
Bioresour Technol. 2023 Feb;370:128580. doi: 10.1016/j.biortech.2023.128580. Epub 2023 Jan 3.
In industrial bioproduction of organic acids, numerous neutralizers are required which substantially increases production costs and burdens the environment. To address this challenge, a Saccharomyces cerevisiae mutant (named TAMC) with a low pH tolerance (pH 2.3) was isolated by adaptive laboratory evolution. Taking the synthesis of l-malic acid as an example, the malate dehydrogenase 3 without signal peptide (MDHΔSKL) and pyruvate carboxylase 2 (PYC2) were overexpressed in cytoplasmic synthesis pathway, and the l-malic acid titer increased 5.6-fold. Subsequently, the malic acid transporter SpMae1 was designed, and the extracellular l-malic acid titer was increased from 7.3 to 73.6 g/L. Furthermore, by optimizing the synthesis of the precursor pyruvate, the titer reached 81.8 g/L. Finally, without any neutralizer, the titer in the 3-L bioreactor reached 232.9 g/L, the highest l-malic acid titer reported to date. Herein, the engineered l-malic acid overproducer paves the way for the large-scale green production of l-malic acid.
在有机酸的工业生物生产中,需要使用大量的中和剂,这大大增加了生产成本,并对环境造成了负担。为了解决这一挑战,通过适应性实验室进化,分离到一株耐酸性低(pH2.3)的酿酒酵母突变株(命名为 TAMC)。以合成 L-苹果酸为例,在细胞质合成途径中过表达了没有信号肽的苹果酸脱氢酶 3(MDHΔSKL)和丙酮酸羧化酶 2(PYC2),L-苹果酸的产量提高了 5.6 倍。随后,设计了苹果酸转运蛋白 SpMae1,使胞外 L-苹果酸的产量从 7.3g/L 提高到 73.6g/L。此外,通过优化前体丙酮酸的合成,产量达到了 81.8g/L。最后,在没有任何中和剂的情况下,3L 生物反应器中的产量达到了 232.9g/L,这是迄今为止报道的最高 L-苹果酸产量。本研究中,工程化的 L-苹果酸高产菌为 L-苹果酸的大规模绿色生产铺平了道路。