Development of a minimal chemically defined medium for Ketogulonicigenium vulgare WSH001 based on its genome-scale metabolic model

• Predictions in GSMM were confirmed by fermentation experiments in CDM.
• Eight essential nutrients for Ketogulonicigenium vulgare were identified.
• MCDM for K. vulgare and co-culture was developed.

Commercial production of 2-keto-l-gulonic acid (2-KLG), the immediate precursor of l-ascorbic acid, is by Ketogulonicigenium vulgare in co-culture with Bacillus megaterium. We used flux balance analysis (FBA) to study a genome-scale metabolic model (GSMM) of K. vulgare, iWZ663, and found that K. vulgare is deficient in nutrient biosynthetic pathways. Individually omitting l-glycine, l-cysteine, l-methionine, l-tryptophan, adenine, thymine, thiamine and pantothenate from complete chemically defined medium (CDM), caused biomass formation of K. vulgare to decrease to 1%, 21%, 16%, 1%, 26%, 57%, 73% and 24%, respectively. Based on these results and FBA, a minimal chemically defined medium (MCDM) was developed that supported monoculture of K. vulgare (0.28 OD600) and 2-KLG production (3.59 g/L), which were similar to those in complete CDM or corn steep liquor powder (CSLP) medium. This study demonstrated the potential of using GSMM and FBA to characterize nutrient requirements, optimize CDM, and study interactions in co-culture.