galU基因在乳酸乳球菌中的克隆及其对胞外多糖产生的影响

从EcoliBL21克隆到UDP-葡萄糖焦磷酸化酶（UGPase）基因galU，与pNZ8048载体连接构建重组表达质粒pNZ8048-galU，进而导入乳酸乳球菌L.lactisL18中，得到重组菌L.lactisL18／pNZS048-galU，研究galU插入对该菌产生胞外多糖的影响。结果显示，在含葡萄糖和乳糖（20：20g／L）的MRS培养基中，重组菌L.lactisL18／pNZ8048-galU在30℃，pH6．5的条件下培养26h，EPS产量最高，为1489．54mg／L；而相同条件下，L．lactisL18培养28h产量最高，为848．93mg／L。二者相比，EPS产量增加了1．75倍。

Cloning of galU Gene in Lactococcus lactis and Its Impact on Exopolysaccharide Production

In the present study, the galU gene from E. coli was ligated to pNZ8008 and introduced into Lactococcus lactis L18, and the effect on the exopolysaccharide production was inspected. The EPS production of L. lactis L18 and recombi-nant L. lactis L18/pNZ8008-galU were compared to test the effect of the inserted gene,which may reflect the activity ofUGPase. Different carbon sources, pH, temperature and cultivation time were tested for EPS production. Under the condi-tions of pH 6.5,30 ℃ and MRS medium adding glucose and lactose(20:20 g/L) ,1489.65 mg/L EPS was produced by L.lactis L18/pNZ8048-galU after 26 h, while 848.93 mg/L EPS was produced by L.lactis L18 after 28 h, the EPS yield from the recombinant was 1.75 times to L. hwtis L18.