海藻糖合成酶产生菌筛选、鉴定及其产酶特性

以麦芽糖为唯一碳源高盐培养基，经高温培养，从温泉水样及其附近土壤中筛选得到一株菌株T2，经过生物合成途径初步验证，该菌株产海藻糖合酶，能够通过海藻糖合成酶（TreS）途径将麦芽糖转化为海藻糖。菌株T2为革兰氏阳性菌，杆状，有芽孢，经过生物学鉴定，将其初步鉴定为芽孢杆菌属（Bacillus sp.）。对其产海藻糖合酶的酶学性质进行了研究：酶反应最适作用温度为60 ℃，在60 ℃条件下保温100 min仍能保持酶活性80.7%；最适作用pH值为7.0，在pH 6.0～7.5范围内稳定。采用正交试验对其发酵培养基配方进行了优化研究，确定了最佳的培养基组成为牛肉膏3.0 g/L，麦芽糖20.0 g/L，蛋白胨7.5 g/L，无机盐（K2HPO4＋NaH2PO4＋MgSO4·7H2O）3.0 g/L。在此条件下，菌株T2产海藻糖合酶酶活力达到310.6 U/L。

Screening and identification of a trehalose-producing strain and its enzyme-producing characteristics

Through the method of high NaCl concentration cultivation with maltose as single carbon source, a strain T2 producing trehalose synthase was screened from hot springs water and nearby soil. By primarily biosynthetic validation, the results showed that strain T2 produced trehalose synthase, and it could convert maltose into trehalose by trehalose synthase (TreS) path. The cells were gram-positive, rods, endospores, and strain T2 was primary identified as Bacillus sp. by biological identification. The enzymatic characteristics of trehalose synthase were studied, it showed that the optimum reaction temperature and pH were 60 ℃ and 7.0, respectively. After incubation at 60 ℃ for 100 min, it remained 80.7% of its activity. The enzyme was stable in the range of pH 6.0-7.5. Compositions of medium was optimized by L9(34) orthogonal experiments, and the optimum medium compositions were beef extract 3.0 g/L, maltose 20.0 g/L, peptone 7.5 g/L, inorganic salt (K2HPO4＋NaH2PO4＋MgSO4·7H2O) 3.0 g/L. The trehalose synthase activity of the strain T2 was up to 310.6 U/L under the optimized conditions.