From molasses to purified α-ketoglutarate with engineered Corynebacterium glutamicum

Abstract

α-ketoglutarate (AKG) is a valuable dicarboxylic acid with multiple applications in the food, pharmaceutical, and chemical industries. Its chemical synthesis is associated with toxic by-products, low specificity, and high energy input. To create a more environmentally friendly and sustainable alternative, a microbial production process for AKG was developed. Four potential producer strains were generated by metabolic engineering of Corynebacteriumglutamicum and characterized on defined glucose/sucrose media as well as molasses, a side stream from sugar beet processing. While strain C.glutamicum P_O6-iolT1Δgdh ΔgltB mscCG' ΔodhA was not able to grow on defined media it outperformed all predecessor variants on molasses. Successful scale-up into a fed-batch bioreactor process with molasses yielded 96.2g AKG with a conversion yield of 0.64gg^-1. Finally, downstream processing by liquid-liquid extraction with ethyl acetate enabled product purification with an extraction efficiency of 87 % and an AKG purity of > 93 %.

Keywords: Bioeconomy; Bioplastics; Bioprocess development; Corynebacterium glutamicum; Metabolic engineering; Molasses; Waste stream; α-ketoglutarate.