利用德氏乳杆菌全酶液水解牛乳酪蛋白

Hydrolysis of Milk Casein with Lactobacillus delbrueckii subsp. bulgaricus Holoenzyme

采用响应面法优化超声破碎工艺获取乳酸菌的全酶液,探讨超声破碎功率、超声破碎时间以及溶菌酶的添加量对超声破碎的影响,对获取的全酶液进行水解脱脂乳及酪蛋白的实验。结果表明:随着超声破碎功率的加大,超声破碎时间的增加,所得酶活力值均呈现先增长后下降的趋势,分析所得的回归方程确定最佳工艺修正参数为:超声破碎仪设定功率71%,超声破碎仪设定时间7.5 min,体系中溶菌酶的添加量290μL/30 mL菌液。在此条件下获取的全酶液水解脱脂乳及酪蛋白显示,超声破碎的过程对酶活力有较大损失,分开处理其胞内和胞外酶液,水解脱脂乳和酪蛋白所获得游离氨基氮的含量分别提高了223.86%和324.11%,高效液相色谱分析结果也证明全酶液水解所得多肽含量及肽段大小多样性均有所提高。

Response surface methodology （RSM） was employed to optimize ultrasonic power,irradiation time and lysozyme dose for the release of holoenzyme from Lactobacillus delbrueckii subsp.bulgaricus.Experiments were conducted to investigate the hydrolysis of skim milk and casein with the holoenzyme.Results indicated that the enzyme activity rose at first and then declined with increasing ultrasonic power and extended irradiation time.From the proposed regression model,the optimal conditions for holoenzyme release were determined as ultrasonication for 7.5 min at a power of 71％ and hydrolysis with lysozyme at a dose of 290 μL/30 mL of cell suspension.The whole fermentation broth of Lactobacillus delbrueckii subsp.bulgaricus was treated under these conditions to obtain holoenzyme 1 or centrifugally separated into cells and supematant.The cells were individually treated under the same conditions and combined with the supernatant to obtain holoenzyme 2.The content of free amino nitrogen in hydrolyates of skim milk and casein by holoenzyme 2 was increased by 223.86％ and 324.11％,respectively,when compared with holoenzyme 1.This may be attributed to losses of extracellular enzyme activities caused by ultasonication.HPLC analysis showed that polypeptides with diverse molecular weight distribution were generated in higher amounts by using the whole enzymes than extracellular enzymes alone.