發(fā)布時(shí)間：2018-03-08 22:07

  本文選題：乳酸菌　切入點(diǎn)：鐵　出處：《西北農(nóng)林科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：乳酸菌,作為一類世界一般公認(rèn)安全的食用細(xì)菌(General Regard As Safety,GRAS),在食品工業(yè)中已被廣泛應(yīng)用,其所具備的突出益生特性及保健功能使之成為微生物研究中的熱點(diǎn)。利用微生物富集微量元素一直是功能食品研究的熱門方向,這其中,元素富集型酵母的研究最為廣泛。而近年來的研究表明,乳酸菌也能夠通過自身的理化作用,對(duì)絕大多數(shù)微量元素起到富集及有機(jī)態(tài)轉(zhuǎn)化。乳酸菌的這種元素富集能力對(duì)于菌體自身以及人體營(yíng)養(yǎng)元素需求均具有重要意義,其在益生的同時(shí),還可以提高及改善人體健康,具有巨大的應(yīng)用前景。本研究以實(shí)驗(yàn)室保藏的清酒乳桿菌清酒亞種WY1,WY2;植物乳桿菌WY3,WY4;短乳桿菌WY5;酒酒球菌WY6;保加利亞乳桿菌WY7及嗜熱鏈球菌WY8為試驗(yàn)菌株,分別探究其對(duì)于鐵、鋅、硒元素的富集能力,并測(cè)試其元素富集后,菌株的體外抗氧化、還原力、膽鹽耐受力及抗菌活性變化�？紤]到發(fā)酵乳制品,尤其是酸奶的市場(chǎng)普遍性需求,結(jié)合前期試驗(yàn)結(jié)果,著重研究酸奶中常見的保加利亞乳桿菌WY7和嗜熱鏈球菌WY8,對(duì)其進(jìn)行元素富集條件優(yōu)化,探究其最大富集率,并進(jìn)一步測(cè)試其體外抗氧化活性。體外抗菌試驗(yàn)中,富硒后的菌株表現(xiàn)出優(yōu)良的抗菌活性;因此,對(duì)于保加利亞乳桿菌和嗜熱鏈球菌富硒后的抗菌活性做進(jìn)一步深入研究。通過以上試驗(yàn)得到了以下結(jié)論:(1)來自不同種屬的8株乳酸菌,對(duì)于無(wú)機(jī)態(tài)鐵、鋅、硒均有較好的富集作用,其元素富集率較高。樣品干法消化后采用原子吸收法,在適宜的鐵質(zhì)量濃度下,測(cè)定菌株的富鐵率由高到低依次為WY6(85.36±1.85%)、WY1(73.74±1.64%)、WY8(73.01±1.25%)、WY5(62.42±0.79%)、WY7(42.69±0.89%)、WY2(39.18±0.94%)、WY3(35.56±1.69%)和WY4(33.33±1.01%);在適宜鋅質(zhì)量濃度下,菌株富鋅率依次為WY6(69.25±1.19%)、WY7(59.03±0.90%)、WY1(54.54±1.38%)、WY5(43.42±0.88%)、WY8(36.35±1.02%)、WY4(32.73±1.02%)、WY2(25.78±0.94%)和WY3(24.78±0.53%);同樣,采用3,3’-二氨基聯(lián)苯胺(3,3’-DAB)比色法,測(cè)出在適宜硒質(zhì)量濃度下,菌株富硒率依次為WY8(79.19±3.01%)、WY7(78.72±1.07%)、WY6(73.42±1.61%)、WY5(67.65±3.24%)、WY1(64.27±3.31%)、WY3(61.49±4.49%)、WY2(56.29±3.01%)和WY4(34.98±1.46%)。體外試驗(yàn)中,元素富集后形成的富鐵、富鋅及富硒菌株,在1,1-二苯基-2-三硝基苯肼(DPPH)、2'-聯(lián)氨-雙-3-乙基苯并噻唑啉-6-磺酸(ABTS)自由基清除率以及還原力方面均有一定的提高;富集后的菌株膽鹽耐受力也有所增強(qiáng);此外,富鐵、富鋅及富硒菌株對(duì)于大腸桿菌以及鼠傷寒沙門氏菌的抗菌作用相比于對(duì)照組提高較為顯著。其中,富鐵及富硒菌株的體外抗氧化及抗菌活性變化最為顯著。(2)以WY7和WY8為富鐵測(cè)試菌株,在單因素試驗(yàn)基礎(chǔ)上,確定起始pH、接種量、培養(yǎng)溫度取值范圍,通過響應(yīng)面優(yōu)化確定WY7最佳富鐵條件為:培養(yǎng)液起始pH 6.7,接種量5.86%,培養(yǎng)溫度35.55℃,富鐵率為52.14%;WY8為:培養(yǎng)液起始pH 7.23,接種量6.06%,培養(yǎng)溫度40℃,富鐵率為97.05%。(3)以WY7和WY8為富硒測(cè)試菌株,以單因素試驗(yàn)結(jié)果為基礎(chǔ),通過響應(yīng)面優(yōu)化,分別確定其最佳富硒培養(yǎng)條件:WY7的最佳富硒條件為起始pH 5.96,接種量6.73%,培養(yǎng)溫度33.24℃,富硒率為94.34%;WY8的最佳富硒條件為起始pH 6.37,接種量6%,培養(yǎng)溫度40℃,富硒率為97.05%。通過傅里葉變換近紅外光譜儀,對(duì)富硒乳酸菌進(jìn)行定性分析,確定了富硒菌具有相同或相似的吸收峰及官能團(tuán);通過電鏡掃描結(jié)合X射線光譜法,確定了富硒乳酸菌細(xì)胞表面單質(zhì)硒的存在。(4)以WY7和WY8為試驗(yàn)菌株,通過平板菌落計(jì)數(shù)法確定適合菌株生長(zhǎng)的富硒濃度為80μg/mL,并在此濃度下制備富硒乳酸菌,采用3,3’-二氨基聯(lián)苯胺(DAB)比色法測(cè)定其富硒量分別為12.05±0.43μg/mL和11.56±0.25μg/mL。制備乳酸菌發(fā)酵濾液,菌體懸液及菌液,通過牛津杯雙層平板法,測(cè)試其對(duì)于大腸桿菌、鼠傷寒沙門氏菌、單增李斯特菌及金黃色葡萄球菌的抑菌效果,結(jié)果表明乳酸菌發(fā)酵濾液和菌液表現(xiàn)出較強(qiáng)的抗菌活性,其中,富硒菌各部分的抗菌活性更為顯著。通過OD值的測(cè)定考察不同乳酸菌發(fā)酵濾液對(duì)于四種致病菌生長(zhǎng)曲線的影響,證明了富硒菌的發(fā)酵濾液能夠明顯延遲致病菌的對(duì)數(shù)期及穩(wěn)定期,降低其生長(zhǎng)速率。此外,同一時(shí)間,相同處理下,與未富硒的乳酸菌相比,富硒菌的發(fā)酵濾液對(duì)四種致病菌細(xì)胞結(jié)構(gòu)均造成了更大的損傷。證明了富硒菌具有更強(qiáng)的抗菌活性。
[Abstract]:Lactic acid bacteria, as a kind of world generally recognized as safe edible bacterium (General Regard As Safety, GRAS), has been widely used in the food industry, with its outstanding probiotic properties and health care function becomes the focus of research. The use of microbial microbial enrichment of trace elements has been a hot research direction, functional food the study, enrichment type yeast is the most widely used. But recent studies show that lactic acid bacteria can also through physical and chemical effects of their own, to the enrichment and organic transformation of most trace elements. The element enrichment ability of lactic acid bacteria are of important significance for the cell itself and human nutrition in the presence of it, at the same time, also can improve and improve human health, it has great application prospect. In this study, the laboratory preserved l.sake wine subspecies WY1 WY2; plant lactobacillus Bacteria WY3 WY4; Lactobacillus brevis WY5; Oenococcus oeni WY6; Lactobacillus bulgaricus and Streptococcus thermophilus WY7 WY8 strain, respectively, for exploring the iron, zinc, selenium enrichment capability, and to test its enrichment, strains in vitro antioxidant and antibacterial activity, reducing power, changes of bile tolerance considering the fermented dairy products, especially the general requirements of yogurt Market, combined with the previous experimental results, focusing on the common yoghurt of Lactobacillus bulgaricus and Streptococcus thermophilus WY7 WY8, the enrichment conditions, explore the maximum accumulation rate, and further test its antioxidant activity in vitro. The in vitro antibacterial test. After the se strains showed excellent antibacterial activity; therefore, for Lactobacillus bulgaricus and Streptococcus thermophilus enriched after antibacterial activity to do further research. Through the above experiment was the following conclusions: (1) to 鑷笉鍚岀灞炵殑8鏍鉤閰歌弻,瀵逛簬鏃犳満鎬侀搧,閿，

本文編號(hào)：1585736