Development of chemically defined media supporting high cell density growth of Ketogulonicigenium vulgare and Bacillus megaterium

The immediate precursor of L-ascorbic acid, or vitamin C, is 2-keto-l-gulonic acid (2-KLG). This is commonly produced commercially by Ketogulonicigenium vulgare and Bacillus megaterium, using corn steep liquor powder (CSLP) as an organic nitrogen source. In this study, the effects of the individual CSLP components (amino acids, vitamins, and metal elements) on 2-KLG production were evaluated, with the aim of developing a complete, chemically defined medium for 2-KLG production. Forty components of CSLP were analyzed, and key components were correlated to biomass, 2-KLG productivity, and consumption rate of L-sorbose. Glycine had the greatest effect, followed by serine, biotin, proline, nicotinic acid, and threonine. The combination of 0.28 g L−1 serine, 0.36 g L−1glycine, 0.18 g L−1 threonine, 0.28 g L−1proline, 0.19 g L−1nicotinic acid, and 0.62 mg L−1biotin in a chemically defined medium produced the highest maximum biomass concentration (4.2 × 109 cfu mL−1), 2-KLG concentration (58 g L−1), and yield (0.76 g g−1) after culturing for 28 h.