摘要
乳酸菌自身不能直接利用外源蛋白质,必须通过蛋白水解体系水解外源蛋白质,生成供菌体正常生长需要的短肽和游离氨基酸。该研究选择6株保加利亚乳杆菌(KLDS1.0207、1.0501、1.1007、1.9201、1.9203、1.0208)进行脱脂乳发酵,在mRNA转录水平上,应用实时荧光定量PCR技术,探讨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)在菌体不同生长阶段表达的动态变化。结果表明,所有菌株生长曲线均呈S型。随着菌体在脱脂乳中的不断生长,蛋白水解活力极显著增强(P<0.01),7个目的基因相对表达量呈现总体上调。6株菌的prtB和oppD基因在对数期的相对表达量极显著高于对照组(4h)(P<0.01)。对数期的胞内肽酶基因(pepC、pepF、pepQ、pepX、pepT)的表达量与对照组(4 h)相比,呈极显著上调(P<0.01),但菌株KLDS 1.0207的pepQ基因在对数期下调,而稳定期上调。由此可见,蛋白水解活力较高的菌株,其生长和产酸特性也较高;发现在脱脂乳中培养保加利亚乳杆菌,其关键蛋白酶基因的表达量呈时间依赖性,且菌株间各蛋白酶基因表达量有较大差异。
Lactic acid bacteria （LAB） obtain all the necessary small peptides and free amino acids through their complex proteolytic system because LAB itself can not directly use the exogenous proteins. In this study, six Lactobacillus delbrueckii subsp, bulgaricu strains （KLDS 1. 0207,1. 0501,1. 1007,1. 9201,1. 9203,1. 0208 ） were incubated in skim milk to analyze the dynamic changes of the genes expressions of the key proteinase （prtB, oppD, pepC, pepF, pepQ,pepX and pepT） at the mRNA transcription level using the real-time quantitative PCR technique. The growth curves of all incubated strains were the S-shaped growth. The proteolytic activities of the six strains incubated in skim milk were significant increase （P 〈0.01 ） , and the genes expressions of seven target genes were unregulated with the continuous growth. The prtB and oppD gene expressions of the six strains were significantly higher in logarithmic phase than those in the control group （4h） （P 〈 0.01 ）. The genes expressions of intracellular peptidase （pepC, pepF, pepQ, pepX, and pepT） showed significant increase at the logarithmic phase compared with the control group （P 〈0.01 ） , however the pepQ gene expression of the KLDS 1. 0207 strain was downregulated at the logarithmic phase, and unregulated in the stable phase. The results indicated that the strains with higher proteolytic activity had better growth and acidification. The key protease genes expressions of Lactobacillus debreuckii ssp. bulgaricus incubated in the skim milk were time-dependent, wherein significant differences were also observed.
出处
《食品与发酵工业》
CAS
CSCD
北大核心
2014年第3期13-19,共7页
Food and Fermentation Industries
基金
黑龙江省新世纪人才项目(1253-NCEF-006)资助
