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目的从云南豆豉样品中筛选产β-半乳糖苷酶的乳酸菌,并对其产酶条件进行研究。方法从云南省元阳、红河、建水、石屏等地采集豆豉样品,并从中分离得到355株微生物。结果经明胶诱导、脱脂乳平板实验,复筛得到87株蛋白酶产生菌,从中筛选产β-半乳糖苷酶的乳酸菌。通过X-Gal平板实验,共获得34株产β-半乳糖苷酶菌株,通过酶活测定,最终筛选得到1株高产β-半乳糖苷酶菌株GJ-1-3L,经16S rDNA序列分析鉴定为短乳杆菌;GJ-1-3L在以葡萄糖为碳源、多聚蛋白胨为氮源、起始pH 6.5的MRS培养基中,接种量为4%,35℃发酵培养12 h,其β-半乳糖苷酶活性高达6.73 U/mL,Cu2+、Ba2+对酶活有抑制作用,而K2HPO4、MgSO4则能促进酶活。结论 GJ-1-3L菌株来源于豆豉,能够产生β-半乳糖苷酶发酵乳糖,同时产生乳酸,其在食品与乳品加工等方面具有很好的应用前景。
Objective To screen β-galactosidase-producing lactic acid bacteria from samples of Yunnan bean curd and study the conditions of its production. Methods Thunbergii samples were collected from Yuanyang, Honghe, Jianshui and Shijing in Yunnan Province, and 355 microorganisms were isolated from them. Results 87 strains of protease-producing bacteria were obtained by gelatin-induced, skim milk and flat-screen screening, and lactic acid bacteria producing β-galactosidase were screened out. A total of 34 β-galactosidase-producing strains were obtained by X-Gal plate assay. One strain of GJ-1-3L with high yield of β-galactosidase was finally screened by enzymatic activity and identified by 16S rDNA sequence analysis Lactobacillus brevis; GJ-1-3L in glucose as a carbon source, polypeptone as a nitrogen source, the initial pH 6.5 MRS medium, inoculum size of 4%, 35 ℃ fermentation 12 h, β- The activity of galactosidase was up to 6.73 U / mL, while Cu2 + and Ba2 + inhibited the enzyme activity, while K2HPO4 and MgSO4 promoted the enzyme activity. Conclusion The strain GJ-1-3L is derived from the kidney bean, which can produce β-galactosidase to ferment lactose and produce lactic acid, which has good application prospect in the processing of food and dairy products.