研究了短乳杆菌NCL912在酸性环境下的生长及在pH2.0极端酸性环境中的耐酸性能。比较了在含L-谷氨酸钠与不含L-谷氨酸钠的培养基中该菌的生长、耐酸性、γ-氨基丁酸产量及谷氨酸脱羧酶活力,并对其耐酸机理进行了分析。结果表明,短乳杆菌NCL912在pH>3.0的酸性环境中可以生长,在pH5.0的培养基中生长较好,在pH 2.0的培养基中可以存活4～6 h。含L-谷氨酸钠培养基中细菌生长较好,在pH 4.0时,L-谷氨酸钠全部转化为γ-氨基丁酸,产量达11.44 g/L;在2种培养基中细菌的存活率存在显著性差异(P<0.05),谷氨酸脱羧酶活力也存在显著性差异(P<0.05),含L-谷氨酸钠培养基中细菌耐酸性强,酶活力高。由此可见,短乳杆菌NCL912能够耐受低pH的原因可能与γ-氨基丁酸的生成有关,即其耐酸机制可能是谷氨酸-γ-氨基丁酸对向运输机制。

The growth of Lactobaillus brevis NCL912,a γ-aminobutyric acid high-yielding strain,in acid environment and its acid tolerance in extreme acid environment(pH 2.0) were investigated in this paper.Meanwhile,the comparision of the growth,acid resistance,the yield of γ-aminobutyric acid and glutamate decarboxylase activity were determined in the media with and without the addition of L-glutamate sodium(L-MSG).The results showed that Lactobaillus brevis NCL912 could grow at pH>3.0,grow well at pH 5.0,and could survive for more than four hours at pH 2.0.The addition of L-MSG can enhance the growth of the strain.L-MSG was converted completely to γ-aminobutyric acid at pH4.0.In addition,the survival percentage(%) and the glutamate decarboxylase activity in the media with and without L-MSG were significantly different(P<0.05).The survival percentage(%) and the glutamate decarboxylase activity were better in the media with L-MSG.It was implied that the acid resistance of Lactobaillus brevis NCL912 was related to glutamate-γ-aminobutyric acid antiporter system.