氮源对德氏乳杆菌保加利亚亚种B61-3耐冻干能力的影响

本研究针对德氏乳杆菌保加利亚亚种B61-3，分别测定了其对16种氮源的利用情况，筛选出能够提高菌株冻干耐受的氮源种类及添加量，并进一步测定该氮源对菌株冻干粉发酵活力、菌体形态、发酵关键酶活力的影响。结果表明：氮源为30 g/L牛骨蛋白胨时可提高菌株冻干存活率及冻干粉发酵活力，冻干存活率由9.68%提高到18.90%，冻干粉平均发酵活力较对照组提高22.15%；电子显微镜显示，牛骨蛋白胨培养后菌体大小及形态有所改变，对照组发酵菌体表现出不规则、卷曲的形态且菌体较长，而牛骨蛋白胨为氮源时菌体形态呈表面光滑的短杆状，菌体长径比(l/d)和面积体积比(S/V)显著降低(P<0.05)，可能与菌株更高的存活率和发酵活力有关。发酵关键酶活力测定结果表明，冷冻干燥显著降低菌株酶活力(P<0.05)，牛骨蛋白胨培养菌株冻干后胞内酶活力均显著高于对照组(P<0.05)，乳酸脱氢酶、Na⁺K⁺-ATP酶及β-半乳糖苷酶分别较对照组提高1.30、1.52及2.75倍，且胞外β-半乳糖苷酶活性低于对照组。结果证实，牛骨蛋白胨培养B61-3菌体能够抵...

Effect of Nitrogen Source on Freeze-dried Resistance of Lactobacillus delbrueckii subsp. bulgaricus B61-3

In this study, the utilization of 16 nitrogen sources of Lactobacillus delbrueckii subsp. bulgaricus B61-3 were determined, and the types and amounts of nitrogen sources that can improve the freeze-drying tolerance of the strain were screened out. More importantly, the effects of nitrogen source modification on the fermentation performance, cell morphology and enzyme activities of freeze-dried powder of the strain were investigated. The results showed that 30 g/L of bovine bone peptone improved the freeze-drying survival rate from 9.68% to 18.90%, and increased fermentation activity by 22.15% compared with the control group. Changed cell size and morphology of the cultured cells of bovine bone peptone were also observed by electron microscope. Cell cultured in bovine bone peptone medium represented a short rod with smooth surface, and the ratio of length to diameter or area to volume decreased significantly (P<0.05). However, cells in the control group showed irregular, curly shape and longer cells. Freeze-drying significantly reduced the enzyme activity of the strain (P<0.05). Compared with control group, the intracellular activities of these enzymes in the cells cultured in bovine bone peptone significantly increased after freeze-drying (P<0.05), and the activities of lactate dehydrogenase, β-galactosidase and Na+K+-ATPase increased by 1.30 times, 1.52 times and 2.75 times respectively, while the extracellular activities of β-galactosidase decreased. Meanwhile, the results showed that B61-3 cells cultured with bovine bone peptone could resist the damage of cell membrane caused by freeze-drying process, reduce the leakage of enzymes, thus improving the freeze-drying survival rate and fermentation activity.