德氏乳杆菌保加利亚亚种IMAU80319高密度发酵和真空冷冻干燥工艺的研究

发布时间：2018-04-19 09:57

  本文选题：德氏乳杆菌保加利亚亚种 + 培养基优化　； 参考：《内蒙古农业大学》2015年硕士论文

【摘要】：德氏乳杆菌保加利亚亚种是酸奶发酵剂中的重要菌种,但国内直投式发酵剂的活菌数和活力均相对较低。筛选优良发酵特性的保加利亚乳杆菌,并研究其高密度发酵和真空冷冻干燥工艺对提高具有自主知识产权的高品质直投式发酵剂并降低乳品企业生产成本有重要意义。本研究以优良菌株ND02为对照,对171株德氏乳杆菌保加利亚亚种的发酵特性极其发酵乳的品质进行研究,筛选出8株具有优良发酵特性及发酵乳感官得分较高的菌株。以ATCC11842为对照菌株,进一步筛选得到对噬菌体phiLdb有抗性的菌株IMAU80319和MAU20422。以MRS为基础培养基,对筛选出的IMAU80319依次进行碳源、氮源、缓冲盐以及无机盐的筛选,通过Box-Behnken Design试验设计得到最优培养基方案为：葡萄糖：1.67%,碳源B：1.67%,乳糖：1.12%,氮源B：1.69%,氮源C：1.69%,牛肉膏：1.13%,KH2PO4:1.33%,NaOH溶液：0.23%,MnSO4:0.05%, CaCl2:0.31%。通过对其静态培养的研究确定其最优工艺为6%的接种量,发酵温度为41℃的,初始的pH值为6.6。以最优培养基与静态培养条件为基础,得到IMAU80319的最佳高密度发酵工艺为：发酵温度41℃,中和剂为25%的氨水,恒pH值为5.0。对IMAU80319的真空冷冻干燥工艺以及保护剂进行优化,得到最佳真空冷冻干燥工艺为-40℃下预冻8h,菌泥与保护剂的最佳比例为1：6。对IMAU80319真空冷冻干燥保护剂配方中添加的糖类、醇类以及盐类进行筛选,得到保护剂最优配方。经过优化后,德氏乳杆菌保加利亚亚种IMAU80319发酵液的活菌数可达到57×108CFU/mL,发酵时间为6-6.5h,与静态培养相比较,发酵时间缩短了3h左右；真空冷冻干燥菌粉中活菌数为11×1010CFU/g,存活率达到83.9%,比优化前提高约30%。
[Abstract]:Lactobacillus de bulgaricus subspecies is an important strain in yoghurt starter, but the number and activity of live bacteria in domestic starter are relatively low.Screening Lactobacillus bulgaricus with good fermentation characteristics and studying its high-density fermentation and vacuum freeze-drying technology are of great significance to improve the high quality direct-cast starter with independent intellectual property rights and reduce the production cost of dairy enterprises.In this study, the fermentation characteristics and the quality of fermented milk of 171 Lactobacillus de bulgaricus subspecies were studied, and 8 strains with good fermentation characteristics and high sensory score of fermented milk were selected.The strains IMAU80319 and MAU20422 resistant to phage phiLdb were further screened using ATCC11842 as control strain.Based on MRS medium, the selected IMAU80319 was screened for carbon source, nitrogen source, buffer salt and inorganic salt in turn.The optimum medium was designed by Box-Behnken Design experiment: glucose: 1.67, carbon: 1.67, lactose: 1.12, nitrogen: 1.69, nitrogen: 1.69, N: 1.69, beef paste: 1.13, KH2PO4: 1.33, NaOH solution: 0.23MnSO40.05, CaCl2: 0.31.Through the study of its static culture, the optimum technology was determined as 6% inoculation, the fermentation temperature was 41 鈩，

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