Two-helper-strain co-culture system: a novel method for enhancement of 2-keto-L-gulonic acid production.

A novel two-helper-strain co-culture system (TSCS) was developed to enhance 2-keto-L-gulonic acid (2-KLG) productivity for vitamin C production. Bacillus megaterium and B. cereus (with a seeding culture ratio of 1:3, v/v), used as helper strains, increased the 2-KLG yield using Ketogulonigenium vulgare compared to the conventional one-helper-strain (either B. cereus or B. megaterium) co-culture system (OSCS). After 45 h cultivation, 2-KLG concentration in the TSCS (69 g l(-1)) increased by 8.9 and 7 % over that of the OSCS (B. cereus: 63.4 g l(-1); B. megaterium: 64.5 g l(-1)). The fermentation period of TSCS was 4 h shorter than that of OSCS (B. cereus). The increased cell numbers of K. vulgare stimulated by the two helper strains possibly explain the enhanced 2-KLG yield. The results imply that TSCS is a viable method for enhancing industrial production of 2-KLG.