pH-DO组合调控策略提高小白链霉菌ε-PL的生物合成

ε-Poly-L-lysine (ε-PL) is a kind of food preservatives mainly produced by Streptomyces albulus, which possesses excellent antimicrobial activity and has broad industrial applications. In this study, the pH and dissolved oxygen (DO) levels in the fed-batch fermentation by an ?-PL high-producing strain S. albulus WG-608 ε-Poly-L-lysine (ε-PL) is a kind of food preservatives mainly produced by Streptomyces albulus, which possesses excellent antimicrobial activity and has broad industrial applications. In this study, the pH and dissolved oxygen (DO) levels in the fed-batch fermentation by an ε-PL high-producing strain S. albulus WG-608 were systemically optimized, and a novel pH-DO regulation strategy was subsequently established. Specifically, the fermentation process was divided into two stages: stage I, DO concentration and pH level were respectively kept at 40% and 4.0, for the accumulation of biomass and ε-PL; stage II, DO and pH levels were maintained at 20% and 4.3, to improve the specific formation rate and ε-PL production. After 240 h of fed-batch fermentation, the ε-PL production and average specific formation rate of WG-608 reached 68.77 ± 2.53 g/L and 2.33 ± 0.08 d-1, which were 28.23% and 12.02% higher than those of the control strategy. Changes in key enzyme activities, respiratory chain activity, and intracellular nucleotide levels were detected and analyzed to further investigate the metabolic differences caused by pH-DO regulation strategy. The result showed that the enhanced glucose consumption rate, central carbon metabolism, respiratory chain activity, L-lysine biosynthesis pathway are responsible for the improved ε-PL production by pH-DO regulation strategy. Overall, the novel pH-DO regulation strategy is a convenient and effective approach for promoting ε-PL biosynthesis by strengthening carbon and energy metabolism. This developed method have shed new light on the ε-PL production by other Streptomyces.608 were systemically optimized, and a novel pH-DO regulation strategy was subsequently established. Specifically, the fermentation process was divided into two stages: stage I, DO concentration and pH level were respectively kept at 40% and 4.0, for the accumulation of biomass and ε-PL; stage II, DO and pH levels were maintained at 20% and 4.3, to improve the specific formation rate and ε-PL production. After 240 h of fed-batch fermentation, the ε-PL production and average specific formation rate of WG-608 reached 68.77 ± 2.53 g/L and 2.33 ± 0.08 d-1, which were 28.23% and 12.02% higher than those of the control strategy. Changes in key enzyme activities, respiratory chain activity, and intracellular nucleotide levels were detected and analyzed to further investigate the metabolic differences caused by pH-DO regulation strategy. The result showed that the enhanced glucose consumption rate, central carbon metabolism, respiratory chain activity, L-lysine biosynthesis pathway are responsible for the improved ε-PL production by pH-DO regulation strategy. Overall, the novel pH-DO regulation strategy is a convenient and effective approach for promoting ε-PL biosynthesis by strengthening carbon and energy metabolism. This developed method have shed new light on the ε-PL production by other Streptomyces.