Engineering Corynebacterium glutamicum for the Efficient Production of 3-Hydroxypropionic Acid from a Mixture of Glucose and Acetate via the Malonyl-CoA Pathway

Abstract

3-Hydroxypropionic acid (3-HP) has been recognized as one of the top value-added building block chemicals, due to its numerous potential applications. Over the past decade, biosynthesis of 3-HP via the malonyl-CoA pathway has been increasingly favored because it is balanced in terms of ATP and reducing equivalents, does not require the addition of costly coenzymes, and can utilize renewable lignocellulosic biomass. In this study, gene mcr encoding malonyl-CoA reductase from Chloroflexus aurantiacus was introduced into Corynebacterium glutamicum ATCC13032 to construct the strain Cgz1, which accumulated 0.30 g/L 3-HP. Gene ldhA encoding lactate dehydrogenase was subsequently deleted to eliminate lactate accumulation, but this decreased 3-HP production and greatly increased acetate accumulation. Then, different acetate utilization genes were overexpressed to reuse the acetate, and the best candidate Cgz5 expressing endogenous gene pta could effectively reduce the acetate accumulation and produced 0.68 g/L 3-HP. To enhance the supply of the precursor acetyl-CoA, acetate was used as an ancillary carbon source to improve the 3-HP production, and 1.33 g/L 3-HP could be produced from a mixture of glucose and acetate, with a 2.06-fold higher yield than from glucose alone. Finally, to inhibit the major 3-HP competing pathway-fatty acid synthesis, 10 μM cerulenin was added and strain Cgz5 produced 3.77 g/L 3-HP from 15.47 g/L glucose and 4.68 g/L acetate with a yield of 187 mg/g substrate in 48 h, which was 12.57-fold higher than that of Cgz1. To our best knowledge, this is the first report on engineering C. glutamicum to produce 3-HP via the malonyl-CoA pathway. The results indicate that the innocuous biosafety level I microorganism C. glutamicum is a potential industrial 3-HP producer.