Using a combined oxygen-supply and substrate-feeding strategy to improve 2,3-butanediol production by metabolically engineered Klebsiella oxytoca KMS005
Résumé
Abstract BACKGROUND There is much demand for and extensive application for 2,3-butanediol (2,3-BD) in various fields, and micro-aerobic and substrate-feeding conditions greatly affect microbial growth and production. The theoretical maximum of 2,3-BD fermentative yield has rarely been reported. Therefore, our study aimed to develop an efficient combined oxygen-supply and substrate-feeding strategy to improve 2,3-BD production yield in metabolically engineered Klebsiella oxytoca KMS005. RESULTS The optimized oxygen consumption for 2,3-BD production by strain KMS005 was demonstrated at 9.2 g for 1 L working volume corresponding to KLa of 25.2 h−1. During fed-batch, a glucose feeding rate of 2 g h−1 starting at the end of the growth phase for 48 h followed by a final batch phase of 40 h was found likely to be satisfactory for 2,3-BD production by the strain KMS005. A final 2,3-BD concentration was obtained at 74.7 g L−1 with few by-products formation. A theoretical maximum of 2,3-BD production yield of 0.5 g g−1 substrate used was also approached. CONCLUSION Our oxygen-supply strategy with the specific feeding pattern developed in this study allowed the highest fermentative production yield of 2,3-BD ever reported. The KMS005 strain may be used as a biocatalyst for cost-effective 2,3-BD production from renewable substrates. In addition, the outcome might bring a message for further developments of simple fed-batch fermentation under micro-aeration conditions into larger scales for 2,3-BD production by K. oxytoca KMS005 or even other microorganisms.
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