氮源对保加利亚乳杆菌关键蛋白酶基因表达的影响

Effect of Nitrogen Sources on Gene Expression of Key Proteolytic Enzyme in Lactobacillus bulgaricus

选择6株保加利亚乳杆菌(KLDS 1.0207,1.0501,1.1007,1.9201,1.9203,1.0208)进行脱脂乳发酵。应用RT-PCR技术,在mRNA转录水平上,探讨不同氮源对保加利亚乳杆菌的蛋白水解体系中关键蛋白酶基因(prtB,oppD,pepC,pepF,pepQ,pepX,pepT)表达的影响。结果表明:在12%脱脂乳中培养12 h,6株保加利亚乳杆菌菌株间的蛋白水解活力存在显著差异(P<0.05);在脱脂乳体系中,添加大豆蛋白胨可以显著下调prt B基因表达(P<0.05),添加酪蛋白胨显著下调6株菌pepC,pepF,pepQ,pepX,pepT基因表达(P<0.05);opp D在不同菌株中的基因表达量趋势不完全相同。添加酵母浸提物,基因的表达量整体呈上调趋势,只有菌株KLDS 1.0208的各目的基因表达量显著下调(P<0.05)。6株菌的蛋白酶基因表达量受培养基质中氮源影响,各基因表达依赖肽供给。

In the study, six Lactobacillus bulgaricus strains（KLDS 1.0207, 1.0501, 1.1007, 1.9201, 1.9203,1.0208） incubated in skim milk were to determine the effects of different nitrogen resource on key proteolytic enzyme genes expressions（prtB, oppD, pepC, pepF, pepQ, pepX, pepT） at the m RNA transcription level using real-time polymerase chain reaction（RT-PCR）. The results showed that there was significant difference in proteolytic activity among strains at 12 h in 12% skim milk（P0.05）. In skim system, adding soy petone significantly down regulated Prt B gene expression（P0.05）, however adding casein peptone sigificantly decreased the gene expressions of pepC, pepF, pepQ,pepX and pepT of 6 strains in skim milk（P0.05）. oppD gene expression trend was not extractly the same among strains. The addition of yeast extract, the amount of gene expression showed an overall upward trend, only the target gene of strain KLDS 1.0208 expression was significantly reduced（P 0.05）. The gene expression of key proteolytic enzyme of the 6 strains was influenced by the nitrogen source in the skim medium, and the expression of each gene was dependent on the peptide supply.