Metabolic Engineering of Lactobacillus plantarum for Fumaric Acid Production Through Activation of the Reductive Branch of the Tricarboxylic Acid Cycle

Abstract

　We report the metabolic engineering of Lactobacillus plantarum, a lactic acid bacterium, for biosynthesis of fumaric acid. A disruptant of the fumarate reductase gene was derived from an L. plantarum lactate dehydrogenase (LDH) -deficient mutant strain, VL103, which accumulated fumaric acid. However, increasing the flux of pyruvate to the TCA cycle did not enhance fumaric acid production; instead, it resulted in the production of lactate. We believe that the fumarate was converted to malate and finally to lactate via the malolactic fermentation pathway. We also observed a marked reduction in cell growth of this mutant strain. Therefore, due to the inefficiency of the fumaric acid transport system in strain VL103, lactic acid accumulation was observed in the cells. We concluded that blocking the malolactic fermentation system and enhancing transporter influx are necessary for application of L. plantarum VL103 in fumaric acid production.