One-Pot Synthesis of beta-Alanine from Maleic Acid via Three-Enzyme Cascade Biotransformation

A novel and efficient one-pot three-enzyme cascade method for the synthesis of beta-alanine from maleic acid was developed. Two recombinant E. coli strains were constructed. The E. coli (MaiA-AspA) co-expressing maleic cis-trans isomerase (MaiA) and L-aspartase (AspA) catalyzed the biotransformation of maleic acid to L-aspartate via fumaric acid, and E. coli (ADC) expressing L-aspartate-alpha-decarboxylase (ADC) catalyzed the bioconversion of L-aspartate to beta-alanine. After systematic optimization of reaction conditions for each strain, the whole cells of two strains were combined for one-pot synthesis of beta-alanine. It was found that the ratio of the two kinds of cells as well as the cell amount play critical roles in the reaction rate and yield of beta-alanine. Adding two kinds of cells in one-pot at the beginning of the reaction was better than adding step by step. Under optimal conditions, the concentration of beta-alanine reached 751 mM after a 9 h reaction, corresponding to a 93.9% yield and 178 g/L/d space-time yield. The developed new route showed application potential for green and efficient biosynthesis of beta-alanine from a cheap substrate by tandem biocatalysts.