Enhancement Of ε-poLy-L-lysine Production Through Feeding Strategy Optimization And Enlarge Trial From5L To30L

ε-poly-lysine (ε-poly-L-lysine, ε-PL) is a natural homotype polymer of L-lysine, and hada wide range of application. As a safe natural preservative, its applications were receivedextensive attention in food industry. After many years of research in the laboratory, we hadbeen initially established several viable strategies to improve the production of ε-PLfermentation. These strategies, in some details were not yet perfect, need to be optimized. Thearticle used the bacterium Streptomyces sp. M-Z18, a producer of ε-PL, as the research object.Start from the optimization of carbon and nitrogen sources’s fed ways, then, we addedglutamic acid and organic nitrogen sources, to increase production and solve cell growthstagnant. At the same time, the fermentation optimization of enlarged from5L fermenter to asmall trial of30L fermenter’s process had been study. Amajor research results are as follows.(1) We examined the effect of different initial glycerol concentration on ε-PL fed-batchfermentation first. The results showed that the best optimal addition concentration of glycerolwas60g/L for Streptomyces sp. M-Z18. On this basis, three kinds of carbon sources feedingstrategy of DO-stat, variable speed feeding strategy and glycerol feedback feeding strategyhad been consulted comparative analysis. The DO-stat feeding strategy was selected to furtheroptimize pulse concentration. When pulse concentration was0-10g/L, the Streptomyces sp.M-Z18synthesized24.16g/L ε-PL at168h. The data was increased about14%comparedwith the glycerol feedback feeding strategy’s21.22g/L.(2) The results of comparative analysis of adding ammonium sulfate in the fed-batchfermentation showed that the variable speed feeding was the best feeding strategy ofammonium sulfate. Feeding glutamic acid fermentation strategy and feeding yeast extractfermentation strategy were established on this basis. Feeding glutamic acid during thefermentation process made the ε-PL production reached31.65g/L at174h. It was49.2%higher than the control production (21.22g/L) of ε-PL. Feeding yeast extract in thefermentation process, binding to the DO-stat feeding under pH two-stage regulation strategy,the ε-PL production reached to38.77g/L at192h, nearly increased by30%compared withthe control (30.11g/L).(3) By compared different pH control strategies, the pH two-stage fermentation strategywas proved more suitable for Streptomyces sp. M-Z18in30L fermenter. By compared flathinges agitator and flat leaf turbine agitator, the agitator type of30L fermenter had lessinfluence of the fermentation of Streptomyces sp. M-Z18. By optimized the inoculum doseand the loaded liquid volume, the highest cell amount of the30L fermenter reached to44.08g/L, and the production to35.2g/L. The production increased by17%compared with the5Lfermenter production’s30.11g/L. The results provided the basis and reference for ε-PLfermentation’s further enlarge.