From molasses to purified α-ketoglutarate with engineered Corynebacterium glutamicum

• Production of α-ketoglutarate using engineered Corynebacterium glutamicum. • Utilization of molasses, a side stream from sugar beet processing. • Fed-batch bioreactor process on molasses with a conversion yield of 0.64 g g - 1 . • Downstream processing by liquid–liquid extraction with ethyl acetate. • Extraction efficiency of 87 % and product purity of > 93 %. 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 Corynebacterium glutamicum and characterized on defined glucose/sucrose media as well as molasses, a side stream from sugar beet processing. While strain C. glutamicum P O6 -iolT 1 Δ gdh Δ gltB mscCG ’ Δ odhA 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 96.2 g AKG with a conversion yield of 0.64 g g −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 %.