Recent advances in metabolic engineering of Corynebacterium glutamicum as a potential platform microorganism for biorefinery

The fermentative production of platform chemicals in biorefineries is a sustainable alternative to current petroleum-refining processes. Industrial microorganisms, such as Escherichia coli, Saccharomyces cerevisiae, and Corynebacterium glutamicum, have been engineered as microbial cell factories that are able to utilize biomass for the production of value-added platform chemicals and polymers. Compared to E. coli and S. cerevisiae, C. glutamicum displays weak carbon catabolite repression and can co-utilize mixed sugars as carbon sources, without any significant growth retardation. Pathways for the utilization of alternative carbon sources, such as d-xylose and l-arabinose from lignocellulosic biomass, lactose and galactose from whey, glycerol from biodiesel, and methanol from natural gas refineries, have been evaluated for chemical production. However, the application of C. glutamicum in biorefineries is limited because it does not secrete hydrolases for the efficient utilization of cellulose, xylan, and starch from lignocellulosic and starch biomass. To solve the limitation, C. glutamicum has been engineered for the consolidated bioprocessing of biomass by the heterologous expression of amylolytic and cellulolytic enzymes. Recently, C. glutamicum has been extensively engineered for polyamide monomer production owing to its ability to produce l-lysine and l-glutamate. This review summarizes recent advances in the development of C. glutamicum strains that can utilize renewable biomass resources for the production of industrially important chemicals. It highlights recent progress in metabolic engineering for the production of polyamide monomers.