Succinate is one of the most important bio-based building block chemical because of its numerous potential applications. However, efficient production of succinate from lignocellulosic feedstock is rarely reported. A study conducted by Yufeng Mao, Guiying Li, and Zhishuai Chang of Tianjin University in China aimed to engineer Corynebacterium glutamicum to efficiently produce succinate from lignocellulosic hydrolysate.

The team first expressed xylA and xylB genes from Xanthomonas campestris in C. glutamicum strain SAZ3 to accelerate xylose consumption and cell growth. Several other genes were also expressed in SAZ3 to achieve succinate production from xylose.

Xylose utilization and succinate production of SAZ3 were further improved by overexpressing SAZ3's tkt and tal genes as well as introducing the araE gene from Bacillus subtilis. The resulting strain, termed C. glutamicum CGS5, showed an excellent ability to produce succinate by consuming a glucose–xylose mixture under anaerobic conditions.

This work introduces an efficient process for the bioconversion of biomass into succinate using a thoroughly engineered strain of C. glutamicum. This microorganism could be a promising platform for succinate production from lignocellulosic feedstock.

For more information, read the article in Biotechnology for Biofuels.

Figure: Succinate biosynthesis pathway of C. glutamicum. The bold black arrows indicate metabolic fluxes increased by overexpression or introduction of the corresponding genes. The gray arrows indicate the reactions leading to a byproduct or presumably irrelevant reactions. Deleted genes are indicated with crosses. Metabolites: G6P glucose-6-phosphate, 6PGL 6-phosphoglucono-1,5-lactone, 6PG 6-phosphogluconate, Ru5P ribulose-5-phosphate, Xu5P xylulose-5-phosphate, R5P ribose-5-phosphate, G3P glyceraldehyde-3-phosphate, S7P sedoheptulose-7-phosphate, F6P fructose-6-phosphate, FBP fructose-1,6-bisphosphate, E4P erythrose-4-phosphate, DHAP dihydroxyacetone, DPG glycerate-1,3-diphosphate, 3PG glycerate-3-phosphate, 2PG glycerate-2-phosphate, PEP phosphoenolpyruvate, PYR pyruvate, AcP acetyl phosphate, AcCoA acetyl-CoA. Genes and their encoded enzymes: iolT encoding myo-inositol permease, glk encoding glucokinase, ptsG encoding glucose-EII of phosphoenolpyruvate phosphotransferase system (PTS), pgi encoding glucose-6-phosphate isomerase, araE encoding a H⁺ symporter protein, xylA encoding xylose isomerase, xylB encoding xylulokinase, zwf and opcA encoding glucose-6-phosphate dehydrogenase, devB encoding 6-phosphogluconolactonase, gnd encoding 6-phosphogluconate dehydrogenase, tkt encoding transketolase, tal encoding transaldolase, pqo encoding pyruvate: quinone oxidoreductase, pta encoding phosphotransacetylase, ackA encoding acetate kinase, cat encoding acetyl-CoA:CoA transferase, aceE encoding pyruvate complex dehydrogenase E1 component, ppc encoding phosphoenolpyruvate carboxylase, pyc encoding pyruvate carboxylase, mdh encoding malate dehydrogenase, gltA encoding citrate synthase, sucE encoding succinate exporter.