Auxotrophic Selection Strategy for Improved Production of Coenzyme B(12) in Escherichia coli

The production of coenzyme B(12) using well-characterized microorganisms, such as Escherichia coli, has recently attracted considerable attention to meet growing demands of coenzyme B(12) in various applications. In the present study, we designed an auxotrophic selection strategy and demonstrated the enhanced production of coenzyme B(12) using a previously engineered coenzyme B(12)-producing E. coli strain. To select a high producer, the coenzyme B(12)-independent methionine synthase (metE) gene was deleted in E. coli, thus limiting its methionine synthesis to only that via coenzyme B(12)-dependent synthase (encoded by metH). Following the deletion of metE, significantly enhanced production of the specific coenzyme B(12) validated the coenzyme B(12)-dependent auxotrophic growth. Further precise tuning of the auxotrophic system by varying the expression of metH substantially increased the cell biomass and coenzyme B(12) production, suggesting that our strategy could be effectively applied to E. coli and other coenzyme B(12)-producing strains.