食品与发酵工业2024，Vol.50Issue(1)：14-21,8.DOI:10.13995/j.cnki.11-1802/ts.035126
基于低pH适应性进化策略提高小白链霉菌ε-聚赖氨酸合成能力
Improvement of ε-poly-L-lysine production by Streptomyces albulus based on low-pH adaptive evolution strategy
摘要
Abstract
Streptomyces albulus is an industrial strain for ε-poly-L-lysine(ε-PL)production.ε-PL is a homopoly(amino acids)pro-duced by S.albulus,which is currently used as an excellent natural food preservative in many countries due to its eminent antibacterial ac-tivity.It often suffers low-pH stress during fermentation,which easily cause a decrease in the capacity of ε-PL biosynthesis.As a result,the adaptive evolution strategy with increasing the selection pressure step by step was introduced to improve the low-pH tolerance of S.al-bulus GS114 in this study.We first determine the initial transfer pH(pH 4.0)and transfer time(36 h)in adaptive evolution strategy.After 93 days of adaptive evolution,the tolerance pH value of S.albulus GS114 is reduced from 4.0 to 3.6.After a lot of strain screening in each selection pH(i.e.pH 4.0,3.8,3.6)in acid tolerance and ε-PL yield,we obtained S.albulus ALE4.0,S.albulus ALE3.8 and S.albulus ALE3.6.We chose spore plate coating and ε-PL shake flask fermentation to evaluate the characteristics of the strains after adaptive evolution.Combined with low pH tolerance and shaker fermentation experiments,it was determined that the optimal adaptive evo-lutionary strain is S.albulus ALE3.6.Further study investigated the influence of pH on the production of ε-PL by S.albulus ALE3.6.Results showed that S.albulus ALE3.6 had significant fermentation advantages under different pH values compared with parent strain S.albulus GS114.In terms of ε-PL production,dry cell weight,ε-PL yield,and ε-PL productivity,S.albulus ALE3.6 had different de-grees of advantages.The ε-PL production of S.albulus ALE3.6 in batch fermentation at pH 4.0,3.8,and 3.6 were reached 4.63,6.14,and 7.2 g/L,respectively,which were enhanced by 13.5％,8.9％and decreased by 7.7％,compared with the original strain S.albulus GS114.Meanwhile,the dry cell weight of S.albulus ALE3.6 was achieved by 16.8,11.8,and 14.7 g/L,respectively,which were decreased to varying degrees compared to the original strain.After comparing the fermentation processes of different pH,we chose pH 4.0 for follow-up study from the point of view of the average specific synthesis rate of the product.Finally,the ε-PL production of S.albulus ALE3.6 in fed-batch fermentation at pH 4.0 were investigated.In a 5 L scale fermentor,ε-PL production of S.albulus ALE3.6 was reached by 43.7 g/L in 192 h,which is 63％higher than the original strain S.albulus GS114.The dry cell weight was at-tained by 39.8 g/L,which was 30％lower than the original strain.S.albulus ALE3.6 had higher ability of cell synthesis per unit and average specific synthesis rate of products in this fermentation process than the original strain.The acquisition of the S.albulus ALE3.6 provided an object for the analysis of the mechanism of acid tolerance.Furthermore,this result showed that the low-pH tolerance of S.al-bulus can be significantly improved through the adaptive evolution method,and enhancing the low-pH tolerance of S.albulus is an effec-tive way to improve its ε-PL production.关键词
小白链霉菌/酸耐受/适应性进化/ε-聚赖氨酸/-聚赖氨酸合成能力Key words
Streptomyces albulus/acid tolerance/adaptive evolution/ε-poly-L-lysine/synthesis ability of ε-poly-L-lysine引用本文复制引用
柳天一,张越,王靓,张宏建,张建华,陈旭升..基于低pH适应性进化策略提高小白链霉菌ε-聚赖氨酸合成能力[J].食品与发酵工业,2024,50(1):14-21,8.基金项目
国家自然科学基金面上项目(31671846) （31671846）
江苏省重点研发计划项目(BE2022703) （BE2022703）
