Production of α-ketoisovalerate with whey powder by systemic metabolic engineering of Klebsiella oxytoca.

Weikang Sun, Shuo Wang, Xiaoxu Tan, Leilei Guo, Wei Liu, Wenjia Tian, Hui Zhang, Tianyi Jiang, Wensi Meng, Yidong Liu, Zhaoqi Kang, Chuanjuan Lü, Chao Gao, Ping Xu, Cuiqing Ma

Microbial cell factories 2024 Oct 05

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Whey, which has high biochemical oxygen demand and chemical oxygen demand, is mass-produced as a major by-product of the dairying industry. Microbial fermentation using whey as the carbon source may convert this potential pollutant into value-added products. This study investigated the potential of using whey powder to produce α-ketoisovalerate, an important platform chemical. Klebsiella oxytoca VKO-9, an efficient L-valine producing strain belonging to Risk Group 1 organism, was selected for the production of α-ketoisovalerate. The leucine dehydrogenase and branched-chain α-keto acid dehydrogenase, which catalyzed the reductive amination and oxidative decarboxylation of α-ketoisovalerate, respectively, were inactivated to enhance the accumulation of α-ketoisovalerate. The production of α-ketoisovalerate was also improved through overexpressing α-acetolactate synthase responsible for pyruvate polymerization and mutant acetohydroxyacid isomeroreductase related to α-acetolactate reduction. The obtained strain K. oxytoca KIV-7 produced 37.3 g/L of α-ketoisovalerate from lactose, the major utilizable carbohydrate in whey. In addition, K. oxytoca KIV-7 also produced α-ketoisovalerate from whey powder with a concentration of 40.7 g/L and a yield of 0.418 g/g. The process introduced in this study enabled efficient α-ketoisovalerate production from low-cost substrate whey powder. Since the key genes for α-ketoisovalerate generation were integrated in genome of K. oxytoca KIV-7 and constitutively expressed, this strain is promising in stable α-ketoisovalerate fermentation and can be used as a chassis strain for α-ketoisovalerate derivatives production. © 2024. The Author(s).

Citation

Weikang Sun, Shuo Wang, Xiaoxu Tan, Leilei Guo, Wei Liu, Wenjia Tian, Hui Zhang, Tianyi Jiang, Wensi Meng, Yidong Liu, Zhaoqi Kang, Chuanjuan Lü, Chao Gao, Ping Xu, Cuiqing Ma. Production of α-ketoisovalerate with whey powder by systemic metabolic engineering of Klebsiella oxytoca. Microbial cell factories. 2024 Oct 05;23(1):264