Production of citramalate in Escherichia coli by mediating colonic acid metabolism and fermentation optimization. (October 2022)

• Record Type: Journal Article
• Authors: Chen, Ai; Xie, Yukang; Xie, Shiqiu; Liu, Yufei; Liu, Min; Shi, Jiping; Sun, Junsong
• Is Part Of: Process biochemistry. Volume 121(2022)
• Page Start: 1
• Page End: 9
• Publication Date: 2022-10
• Subjects: Escherichia coli -- Citramalate -- Rcs system -- Colanic acid; Biochemical engineering -- Periodicals; Biotechnology -- Periodicals; Biochemistry -- periodicals; Biotechnology -- periodicals; Chemical Engineering -- periodicals; Génie biochimique -- Périodiques; Biotechnologie -- Périodiques; Biochemical engineering; Biotechnology; Periodicals; 660.63
• DOI: 10.1016/j.procbio.2022.06.018
• Languages: English
• ISSNs: 1359-5113

Abstract

Abstract: Citramalic acid (citramalate) is important for the chemical synthesis of methylmethacrylate, a bulk monomer used for manufacturing biodegradable polymers. Escherichia coli strains have been engineered for the biological production of citramalate since a rare mutant of citramalate synthase was invented as a mesophilic catalyzer to form the chemical. However, acidic byproducts are routinely excreted by E. coli host cells during fermentation, which could significantly reduce the carbon conversion efficiency of biosynthetic chemicals, including citramalate. Herein, an unusual mutant called S17–3 was reported, and this mutant demonstrated superb recovery efficacy from glucose to citramalate and secreted a very low level of fermentation byproducts during the fermentative production of citramalate. However, S17–3 tends to produce a large amount of colonic acid (CA). Genetically manipulating the regulators involved in CA synthesis revealed that the deletion of rcsD could significantly improve the citramalate titer. Fed-batch fermentation under optimized conditions led to a maximum titer of 46.2 g/L citramalate accumulated in the broth, with a conversion efficiency of 0.80 g citramalate per gram glucose and a close-to-the-theoretical mole transversion efficiency (mol/mol) of 0.97. This study facilitates the development of a practical bioproduction of citramalate using E. coli strains. Graphical Abstract: ga1 Highlights: BL21 (DE3) and S17-3 were engineered and compared for the production of citramalate. rcsD deletion enhanced the citramalate yield in recombinant E. coli S17-3. The highest carbon conversion ratio ever reported was obtained for the production of citramalate from glucose.