外源信号分子AI-2对发酵乳杆菌TG4-1-1和乳酸片球菌11-3产胞外多糖的影响

Effects of Exogenous AI-2 on Extracellular Polysaccharide Productedby Lactobacillus fermentum TG4-1-1 and Pediococcus acidilactici 11-3

研究群体感应信号分子AI-2对发酵乳杆菌TG4-1-1和乳酸片球菌11-3胞外多糖产量的影响,探讨信号分子AI-2对乳酸菌分泌胞外多糖的调控机制。采用苯酚-硫酸法和哈维氏弧菌BB170生物发光法测定菌株不同培养时间胞外多糖产量和AI-2活性,筛选添加最佳浓度的外源信号分子AI-2,测定菌株的生长量、胞外多糖产量、AI-2活性,扫描电镜观察菌体形态及冷冻干燥后多糖形态。结果表明:发酵乳杆菌TG4-1-1和乳酸片球菌11-3均在10 h时AI-2活性最强,22 h时胞外多糖产量最高,分别达到(195.863±1.643)mg/L和(125.179±1.458)mg/L。100μmol/L外源AI-2为菌株TG4-1-1和11-3的最佳添加浓度,而该浓度对两株菌各阶段生长量均无显著影响(P>0.05),对菌株TG4-1-1在16~22 h和菌株11-3在13~22 h的胞外多糖产量有显著促进作用(P<0.05)。同时,显著增强试验菌株在10 h时AI-2的活性(P<0.05)。添加100μmol/L外源AI-2培养13 h后菌体表面光滑,形状规则,形态饱满,其对胞外多糖形态无明显影响。以上结果说明一定浓度的外源AI-2可促进菌株TG4-1-1和11-3胞外多糖的产生,为Lux S/AI-2 QS系统调控胞外多糖研究提供参考。

In this study,the effect of quorum sensing signal molecule AI-2 on EPS production of L.fermentum TG4-1 and P.acidilactici 11-3 was investigated to explore the regulation mechanism of LuxS/AI-2 QS system on EPS secretion of lactic acid bacteria.EPS production and AI-2 activity of strains TG4-1-1 and 11-3 were measured by phenol-sulfuric acid method and V.harveyi BB170 bioluminescence method.The optimal concentration of exogenous AI-2 was selected and the growth,EPS production and AI-2 activity of the strain were measured.The morphology of the strain and polysaccharide after freeze-drying were observed by scanning electron microscopy.The results showed that both strains TG4-1-1 and 11-3 had the strongest AI-2 activity at 10 h,and the highest EPS yield at 22 h,reaching(195.863±1.643)mg/L and(125.179±1.458)mg/L,respectively.After screening,100μmol/L exogenous AI-2 was determined as the optimal supplemental concentration of strains TG4-1-1 and 11-3,which had no significant effect on the growth of the two strains at each stage(P>0.05).EPS production of strain TG4-1-1 at 16~22 h and strain 11-3 at 13~22 h were significantly promoted(P<0.05);meanwhile,the activity of AI-2 was significantly increased at 10 h(P<0.05).After 100μmol/L exogenous AI-2 was added for 13 h,the cells had smooth surface,regular shape and full shape.However,it had no obvious effect on the surface structure and morphology of exopolysaccharides.These results indicated that exogenous AI-2 at a certain concentration could promote the production of EPS in strains TG4-1-1 and 11-3,providing a certain reference for the mechanism of LuxS/AI-2 QS system regulating EPS.