2株鱼源乳酸菌的生物学特性研究

Biological characteristics of two lactic acid bacteria from orange-spotted grouper(Epinephelus coioides)larvae

【目的】研究2株鱼源乳酸菌的生物学特性,为石斑鱼高效益生菌株的筛选提供试验依据。【方法】体外检测乳酸菌EA-1和Y4-2产乳酸及超氧化物歧化酶（SOD）的能力,以及2菌株对不同pH值、胆盐、胃蛋白酶和高温的耐受能力。【结果】菌株EA-1和Y4-2均具有较强的产乳酸能力,培养液中的乳酸含量在96 h内随培养时间延长呈上升趋势,EA-1产乳酸速度相对较快。菌株EA-1和Y4-2均能在培养24 h后产生活性稳定的SOD,培养48h后EA-1产生的SOD活性显著高于Y4-2（P〈0.05）。菌株EA-1和Y4-2经pH 2.5-4.5处理4 h后存活数维持在10^6mL^-1以上,菌株Y4-2对pH 1.5低酸环境的耐受能力强于EA-1。2菌株在1 g/L胆盐质量浓度下存活数均较高;胆盐质量浓度达到2 g/L时,EA-1和Y4-2的存活数可维持在10^5mL^-1以上,提示2菌株对≤2 g/L的胆盐具有一定的耐受性。经4-10 g/L的蛋白酶处理30 min后,EA-1和Y4-2的存活数均维持在10^6mL^-1以上。经60℃处理30min后EA-1和Y4-2的存活数均维持在10^6mL^-1以上,Y4-2对80℃高温的耐受能力较EA-1强,说明EA-1和Y4-2有一定的热耐受性。【结论】EA-1和Y4-2产乳酸和SOD能力均较强,且对低pH值、高胆盐、胃蛋白酶和高温具有一定的耐受能力。

[Objective] Biological characters of 2 strains of lactic acid bacteria were studied to provide theoretic support in good probiotics strain selection for grouper. [Method] Lactic acid and SOD production by lactic acid bacteria strains EA-1 and Y4-2 from Orange-spotted Grouper（Epinephelus coioides）larvae, and the tolerance of the two strains to low pH, bile salt, protease and heat were studied. [Result] EA-1 and Y4-2 exhibited good lactic acid and SOD producing capability. Lactic acid concentration in two cultures increased as incubation proceeded,EA-1 produced lactic acid more rapidly. EA-1 and Y4-2 produced stable amount of SOD after 24 h of incubation,and the amount of SOD produced by EA-1 was significantly higher than Y4-2 after 48 h of incubation （P〈0.05）. The survival counts of Y4-2 and EA-1 were above 10^6 mL^-1 after 4 h of treatment at pH 2.5-4.5. Y4-2 was more tolerant to low pH compared with EA-1. EA-1 and Y4-2 were able to survive well within 1 h incubating with 1 g/L bile salt. The survival counts of Y4-2 and EA-1 were above 10^5 mL^-1 incubating with 2 g/L bile salt,which indicated that Y4-2 and EA-1 could tolerate bile salt concentration under 2 g/L. Pepsin had negative effect on the survival of EA-1 and Y4-2 strains, the survival counts of Y4-2 and EA-1 were above 10^6 mL ^-1 after 30 rain of treatment with 4--10 g/L Pepsin. The survival counts of Y4-2 and EA-1 were above 10^6 mL^-1 after 30 min of treatment at 60 ℃,Y4-2 was relatively more tolerant to high temperature than that of EA-1. [Conclusion] EA-1 and Y4-2 exhibited good lactic acid and SOD producing capability and showed good tolerance to low pH, bile salt, protease and heat.