本文選題：德氏乳桿菌保加利亞亞種 + 培養(yǎng)基優(yōu)化　； 參考：《內(nèi)蒙古農(nóng)業(yè)大學(xué)》2015年碩士論文

【摘要】：德氏乳桿菌保加利亞亞種是酸奶發(fā)酵劑中的重要菌種,但國內(nèi)直投式發(fā)酵劑的活菌數(shù)和活力均相對較低。篩選優(yōu)良發(fā)酵特性的保加利亞乳桿菌,并研究其高密度發(fā)酵和真空冷凍干燥工藝對提高具有自主知識產(chǎn)權(quán)的高品質(zhì)直投式發(fā)酵劑并降低乳品企業(yè)生產(chǎn)成本有重要意義。本研究以優(yōu)良菌株ND02為對照,對171株德氏乳桿菌保加利亞亞種的發(fā)酵特性極其發(fā)酵乳的品質(zhì)進(jìn)行研究,篩選出8株具有優(yōu)良發(fā)酵特性及發(fā)酵乳感官得分較高的菌株。以ATCC11842為對照菌株,進(jìn)一步篩選得到對噬菌體phiLdb有抗性的菌株IMAU80319和MAU20422。以MRS為基礎(chǔ)培養(yǎng)基,對篩選出的IMAU80319依次進(jìn)行碳源、氮源、緩沖鹽以及無機(jī)鹽的篩選,通過Box-Behnken Design試驗設(shè)計得到最優(yōu)培養(yǎng)基方案為：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%。通過對其靜態(tài)培養(yǎng)的研究確定其最優(yōu)工藝為6%的接種量,發(fā)酵溫度為41℃的,初始的pH值為6.6。以最優(yōu)培養(yǎng)基與靜態(tài)培養(yǎng)條件為基礎(chǔ),得到IMAU80319的最佳高密度發(fā)酵工藝為：發(fā)酵溫度41℃,中和劑為25%的氨水,恒pH值為5.0。對IMAU80319的真空冷凍干燥工藝以及保護(hù)劑進(jìn)行優(yōu)化,得到最佳真空冷凍干燥工藝為-40℃下預(yù)凍8h,菌泥與保護(hù)劑的最佳比例為1：6。對IMAU80319真空冷凍干燥保護(hù)劑配方中添加的糖類、醇類以及鹽類進(jìn)行篩選,得到保護(hù)劑最優(yōu)配方。經(jīng)過優(yōu)化后,德氏乳桿菌保加利亞亞種IMAU80319發(fā)酵液的活菌數(shù)可達(dá)到57×108CFU/mL,發(fā)酵時間為6-6.5h,與靜態(tài)培養(yǎng)相比較,發(fā)酵時間縮短了3h左右；真空冷凍干燥菌粉中活菌數(shù)為11×1010CFU/g,存活率達(dá)到83.9%,比優(yōu)化前提高約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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