Gelatin enhances 2-keto-L-gulonic acid production based on Ketogulonigenium vulgare genome annotation

In the two-step fermentative production of vitamin C, its precursor 2-keto-l-gulonic acid (2-KLG) was synthesized by Ketogulonicigenium vulgare through co-culture with Bacillus megaterium. The reconstruction of the amino acid metabolic pathway through completed genome sequence annotation demonstrated that K. vulgare was deficient in one or more key enzymes in the de novo biosynthesis pathways of eight different amino acids (l-histidine, l-glycine, l-lysine, l-proline, l-threonine, l-methionine, l-leucine, and l-isoleucine). Among them, l-glycine, l-proline, l-threonine, and l-isoleucine play vital roles in K. vulgare growth and 2-KLG production. The addition of those amino acids increased the 2-KLG productivity by 20.4%, 17.2%, 17.2%, and 11.8%, respectively. Furthermore, food grade gelatin was developed as a substitute for the amino acids to increase the cell concentration, 2-KLG productivity, and l-sorbose consumption rate by 10.2%, 23.4%, and 20.9%, respectively. As a result, the fermentation period decreased to 43 h in a 7-L fermentor.