The group of Akihiro KONDO at RIKEN has used synthetic biology to produce maleic acid from glucose in recombinant E. coli by a novel pathway. The research team combined 3-hydroxybenzoic acid synthetase (Hyg5) derived from Streptomyces hygroscopicus, 3-hydroxybenzoic acid 6-hydroxylase (3HB6H) derived from Rhodococcus jostii RHA, and maleyl pyruvate synthase (MPS) from Rhodococcus sp. NCIMB 12038. By co-expression of these enzymes with maleyl pyruvate hydrolase (HbzF) derived from Pseudomonas alcaligenes NCIMB 9867 in Escherichia coli, maleic acid was produced at a level of 27 mg/L. Using metabolic engineering to enhance the supply of precursors such as phosphoenol pyruvate, and after optimizing fermentation conditions in a 1 L jar fermenter, yields of 7.1 g/L of maleic acid from glucose were obtained (60 % molar yield). Maleic anhydride, a dehydrated compound of maleic acid, can be converted to various unsaturated polyester resins and pharmaceutical intermediates, and its global market size exceeds 1.8 million tons annually.

RIKEN news release, October 27, 2017