發(fā)布時(shí)間：2018-04-25 14:49

  本文選題：青藏高原 + 乳酸菌�。� 參考：《鄭州大學(xué)》2017年碩士論文

【摘要】：本研究以青藏高原地區(qū)裸鯉腸道、植物表面、土壤為研究材料,對(duì)其附著乳酸菌代表株在極端環(huán)境條件下的耐受性進(jìn)行檢測(cè),探討不同材料來(lái)源乳酸菌極端環(huán)境耐受性的差異,并對(duì)部分優(yōu)良乳酸菌代表株的益生性能進(jìn)行初步研究,以期篩選具有益生潛能的乳酸菌。依照乳酸菌形態(tài)特征、生理生化特點(diǎn),結(jié)合16S rRNA基因序列分析,不同年齡的裸鯉腸道附著乳酸菌大致被歸為4個(gè)屬,分別是Lactobacillus、Leuconostoc、Lactococcus和Pediococcus,分屬8個(gè)種主要為lactococcus lactis、pediococcus acidilactici、pediococcus pentosaceus、leuconostoc mesenteroides、lactobacillus paraplantarum、lactobacillus sakei、lactobacillus fuchuensis、lactobacillus casei等,其中桿菌明顯比比球菌多。分別從裸鯉腸道、植物表面、茶卡鹽湖土壤分離乳酸菌中選擇48株乳酸菌代表株進(jìn)行極端環(huán)境耐受性的檢測(cè)。通過(guò)平板計(jì)數(shù)法以及比濁度來(lái)檢測(cè)乳酸菌在極低pH、高鹽濃度、極端溫度條件下的生長(zhǎng)狀況。結(jié)果發(fā)現(xiàn)所有乳酸菌在pH1的極酸環(huán)境下都不能存活,大部分乳酸菌在pH2的酸性環(huán)境中的生長(zhǎng)明顯受到抑制,部分存活率達(dá)到70%,其中裸鯉腸道分離菌F2-2、F9-10、F12-66能夠生長(zhǎng),顯示極強(qiáng)的酸性耐受性,pH3的酸性環(huán)境下存活率普遍較高,甚至還能生長(zhǎng)。在16%的高鹽濃度下,多株乳酸菌存活率可達(dá)到50%以上,部分能夠生長(zhǎng)。50℃高溫對(duì)乳酸菌的生存造成了嚴(yán)重的威脅,大多數(shù)乳酸菌不能存活,只有極少數(shù)乳酸菌能夠在培養(yǎng)的前12個(gè)小時(shí)得以緩慢的生長(zhǎng)。大多數(shù)乳酸菌在10℃的低溫條件下都能夠良好生長(zhǎng),0℃條件下幾乎不能生長(zhǎng),但F2-1、F11-67、M1-8在培養(yǎng)168h后,OD值達(dá)到0.35,表現(xiàn)出緩慢的生長(zhǎng)趨勢(shì),其中2株為P.pentosaceus。通過(guò)紙片擴(kuò)散法、平板計(jì)數(shù)法檢測(cè)乳酸菌代表株抗生素敏感性以及對(duì)胃腸道環(huán)境的耐受性。結(jié)果顯示乳酸菌主要對(duì)VA、GM、PB、CIP、PG有抗性,對(duì)CHL、AM、TE較為敏感。多數(shù)乳酸菌對(duì)胃腸道環(huán)境耐受性比較差,經(jīng)過(guò)7h的人工模擬胃腸道環(huán)境后乳酸菌存活率比較低甚至全部死亡,其中N20、N7、N6、N1、qz1242耐受性比較強(qiáng),存活率最高為61.11%,最低為31.95%,并且可以發(fā)現(xiàn)耐受性比較好的菌株大多數(shù)為L(zhǎng)actobacillus,其中存活率最高的為分離自土壤中的L.plantarum。人工模擬胃腸道耐受性比較好的乳酸菌通過(guò)平板計(jì)數(shù)法來(lái)檢測(cè)不同膽鹽濃度下的耐受性。膽鹽對(duì)乳酸菌的生長(zhǎng)顯示出抑制性,并且隨其濃度的增加及培養(yǎng)時(shí)間的延長(zhǎng)而逐漸增強(qiáng)。在0.1%的膽鹽濃度下,乳酸菌的存活率比較高,甚至高達(dá)100%,小部分乳酸菌能夠在含0.2%的膽鹽培養(yǎng)基中存活,隨著膽鹽濃度增加到0.3%,大多數(shù)乳酸菌的存活率直線下降為0,耐受性極差。茶卡鹽湖土壤分離乳桿菌N22、N19在0.3%的膽鹽濃度下4h活菌數(shù)為2.70 logcfu/ml,具有一定強(qiáng)度的膽鹽耐受性。
[Abstract]:In this study, the intestinal tract, plant surface and soil of naked carp in Qinghai-Xizang Plateau were used as the research materials, the tolerance of the representative strains of lactic acid bacteria attached to them under extreme environmental conditions was tested, and the differences of extreme environmental tolerance of lactic acid bacteria from different sources were discussed. The probiotics of some representative strains of lactic acid bacteria were studied in order to screen lactic acid bacteria with probiotic potential. According to the morphological characteristics, physiological and biochemical characteristics of lactic acid bacteria and the sequence analysis of 16s rRNA gene, four genera of Lactobacillus leuconostoctus Lactococcus and Pediococcus. belong to 8 species of lactococcus lactis, mainly lactococcus acidilacticipestris pentosaceus pentosaceus Lactobacillus mesenteroideslactobacillus paraplantarum lactobacillus lactobacillus lactobacillus sakeilactobacillus fuchuensis lactobacillus casei. There were more bacilli than cocci. 48 representative strains of lactic acid bacteria were selected from the intestinal tract, plant surface and tea salt lake soil of naked carp to detect their extreme environmental tolerance. The growth of lactic acid bacteria at very low pH, high salt concentration and extreme temperature was detected by plate counting and turbidity. The results showed that all lactic acid bacteria could not survive in the extreme acid environment of pH1. The growth of most lactic acid bacteria in the acidic environment of pH2 was obviously inhibited, and the partial survival rate reached 70%, in which the isolated bacteria F2-2F9-10F12-66 from the intestine of naked carp could grow. The results showed that the survival rate of pH 3 was higher than that of pH 3, and it could even grow. Under the high salt concentration of 16%, the survival rate of many strains of lactic acid bacteria could reach more than 50%, and some of them could grow at 0.50 鈩，

本文編號(hào)：1801787