为了探究德式乳杆菌保加利亚亚种对乳清蛋白的利用能力,研究了8株德式乳杆菌保加利亚亚种菌株在乳清蛋白培养体系中的生长和产酸情况,发酵过程中氨肽酶PepN、PepC和PepX活力变化及乳清蛋白主要组分β-乳球蛋白、α-乳白蛋白和牛血清白蛋白的利用情况,探讨了不同菌株氨肽酶活力变化与乳清蛋白水解能力之间的相关性。结果表明,在乳清蛋白培养体系中,最适宜菌株生长的初始pH是5.5,该条件下菌株在3 h内快速生长到达稳定期。在发酵过程(12 h)中,3种氨肽酶活力均表现出先升高后降低的变化趋势,但不同菌株的酶活力之间存在显著差异性。8株菌株均表现出对α-乳白蛋白较强的水解能力(26.93%~31.33%),但对于β-乳球蛋白的水解能力存在菌株差异性,β-乳球蛋白的变异体A和B的水解率分别是10.56%~22.82%和9.04%~23.83%。菌株的氨肽酶活力与β-乳球蛋白的水解能力之间存在一定相关性,DQHXNS8L6和DQHXNS15M2在3 h内即能达到最高的氨肽酶活力并有效水解β-乳球蛋白,具有发酵乳清蛋白饮料的应用潜力。
In order to investigate the whey protein hydrolytic ability of Lactobacillus delbrueckii subsp. bulgaricus, the growth and acid production of 8 strains of Lactobacillus delbrueckii subsp. bulgaricus in whey protein culture medium were studied, and the aminopeptidase activity of PepN, PepC and PepX and the utilization of β-lactoglobulin, α-lactalbumin and bovine serum albumin were determined during fermentation. The correlation between the activity of aminopeptidase and the ability to hydrolyze whey protein in different strains was also discussed. The results showed that the optimal initial pH for growth was 5.5, and the strain quickly grew to a stable phase within 3 h. The activity of three aminopeptidase was revealed first to rise and then fall during 12-hour fermentation, but significant differences of the aminopeptidase activity were observed between different strains. All 8 strains have strong hydrolytic ability to α-lactalbumin, with a hydrolysis rate ranging from 26.93% to 31.33%. However, there were differences in the hydrolysis ability of β-lactoglobulin, and the hydrolysis rate varied from 10.56% to 22.82% and from 9.04% to 23.83% for β-lactoglobulin variants A and B, respectively. Correlation was found between the activity of three aminopeptidase and the hydrolytic ability of β-lactoglobulin. Strain DQHXNS8L6 and DQHXNS15M2 achieved their highest aminopeptidase activity in 3 h and could effectively degrade β-lactoglobulin, thus had potential application in whey protein beverage production.
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