Research Institute, Kagome Co., Ltd., 17 Nishitomiyama, Nasushiobara 329-2762, Japan.
Curr Microbiol. 2012 Dec;65(6):679-85. doi: 10.1007/s00284-012-0216-2. Epub 2012 Aug 31.
Unlike dairy lactic acid bacteria, Lactobacillus brevis cannot ferment milk. We characterized the lactose utilization by L. brevis KB290. In a carbohydrate fermentation assay using API 50 CHL, we showed during 7 days L. brevis did not ferment lactose. L. brevis grew to the stationary phase in 2 weeks in MRS broth containing lactose as the carbon source. L. brevis slowly consumed the lactose in the medium. L. brevis hydrolyzed lactose and a lactose analog, o-nitrophenyl-β-D-galactopyranoside (ONPGal). This β-galactosidase activity for ONPGal was not repressed by glucose, galactose, fructose, xylose, or maltose showing the microorganism may not have carbon catabolite repression. We purified the L. brevis β-galactosidase using ammonium sulfate precipitation and several chromatographies. The enzyme's molecular weight is estimated at 72 and 37 kDa using SDS-PAGE analysis. The N-terminal amino acid sequence of the larger protein was 90 % similar to the sequence of the putative β-galactosidase (YP_796339) and the smaller protein was identical to the sequence of the putative β-galactosidase (YP_796338) in L. brevis ATCC367. This suggests the enzyme is a heterodimeric β-galactosidase. The specific activity of the purified enzyme for lactose is 55 U/mg. We speculate inhibition of lactose transport delays the lactose utilization in L. brevis KB290.
与乳杆菌不同，短乳杆菌不能发酵牛奶。我们对短乳杆菌 KB290 的乳糖利用进行了表征。在使用 API 50 CHL 的碳水化合物发酵测定中，我们发现短乳杆菌在 7 天内不能发酵乳糖。在含有乳糖作为碳源的 MRS 肉汤中，短乳杆菌在 2 周内生长到稳定期。短乳杆菌缓慢消耗培养基中的乳糖。短乳杆菌水解乳糖和乳糖类似物邻硝基苯-β-D-半乳糖吡喃糖苷（ONPGal）。这种对 ONPGal 的β-半乳糖苷酶活性不受葡萄糖、半乳糖、果糖、木糖或麦芽糖的抑制，表明该微生物可能没有碳分解代谢物抑制。我们使用硫酸铵沉淀和几种色谱法从短乳杆菌中纯化了β-半乳糖苷酶。使用 SDS-PAGE 分析，该酶的分子量估计为 72 和 37 kDa。较大蛋白质的 N 末端氨基酸序列与短乳杆菌 ATCC367 中假定的β-半乳糖苷酶（YP_796339）的序列有 90%的相似性，而较小的蛋白质与假定的β-半乳糖苷酶（YP_796338）的序列完全相同。这表明该酶是一种异源二聚体β-半乳糖苷酶。纯化酶对乳糖的比活性为 55 U/mg。我们推测乳糖转运的抑制会延迟短乳杆菌 KB290 中乳糖的利用。
