【摘要】： 過(guò)量攝入膽固醇引起的心血管疾病嚴(yán)重危害人體健康,如何控制血清膽固醇水平受到越來(lái)越廣泛的關(guān)注。乳桿菌降膽固醇作用雖已被大量報(bào)道,但其優(yōu)良菌株的評(píng)價(jià)標(biāo)準(zhǔn)、明確的去除機(jī)理等方面仍不確定。 本研究首先建立了一套體外評(píng)價(jià)乳桿菌降膽固醇綜合性能的標(biāo)準(zhǔn)。它包括菌株對(duì)模擬胃部pH值的耐受性,對(duì)模擬小腸膽汁濃度的耐受能力,降膽固醇性能——包括共沉淀作用和同化作用的分別評(píng)價(jià),以及膽鹽水解酶(Bile Salt Hydrolase, BSH)比酶活等一系列指標(biāo)。用該標(biāo)準(zhǔn)對(duì)1株唾液乳桿菌和5株植物乳桿菌進(jìn)行評(píng)估,結(jié)果顯示6株菌在各項(xiàng)指標(biāo)上都顯示出菌株的特異性。6株乳桿菌中,植物乳桿菌Lp529在各方面都有優(yōu)秀的表現(xiàn),因此它被選出作為降膽固醇益生菌潛力株,并與1株商業(yè)菌株、植物乳桿菌LpOnlly一起,進(jìn)行后續(xù)的研究。 研究Lp529和LpOnlly的BSH酶活發(fā)現(xiàn)如下特性: 1) BSH酶活不受其底物及底物組成基團(tuán)激活或抑制,顯示出BSH非變構(gòu)酶的性質(zhì)。 2) BSH總酶活累積曲線呈S型,與菌株生長(zhǎng)曲線類(lèi)似;BSH比酶活在菌株對(duì)數(shù)生長(zhǎng)期時(shí)迅速升高,在平臺(tái)期前達(dá)到峰值后又小幅回落并保持穩(wěn)定。 3)模擬人膽汁短時(shí)間可逆調(diào)控BSH比酶活的高低。 4) 2株菌在模擬人膽汁中傳代馴化,結(jié)果BSH比酶活逐代降低,并在第4代后達(dá)到最低值,僅為初始值的60%;同時(shí)降膽固醇能力也隨之降低,而膽鹽耐受性逐漸升高。 5)最后,通過(guò)引入BSH總酶活-膽固醇共沉淀曲線探討并驗(yàn)證了乳桿菌降膽固醇作用的機(jī)理,為前述優(yōu)良菌株的篩選提供理論支持。研究證實(shí),菌株體外降膽固醇是共沉淀與同化共同作用的結(jié)果。在6株菌的去膽固醇效果中,同化作用都強(qiáng)于共沉淀。
[Abstract]:The cardiovascular disease caused by excessive intake of cholesterol is seriously harmful to human health, and how to control the serum cholesterol level has been paid more and more attention. Although the effect of Lactobacillus on cholesterol lowering has been reported widely, the evaluation criteria and clear removal mechanism of Lactobacillus strains are still uncertain. In this study, we first established a set of in vitro evaluation of Lactobacillus cholesterol lowering comprehensive performance. It includes the strain's tolerance to mimic gastric pH values, tolerance to simulated intestinal bile concentration, cholesterol lowering performance-including a separate evaluation of coprecipitation and assimilation, and bile salt hydrolase (Bile Salt Hydrolase, BSH) specific enzyme activity and a series of indicators. The standard was used to evaluate one Lactobacillus saliva and five Lactobacillus plantarum strains. The results showed that all the 6 strains showed the specificity of the strains in each index. Among the 6 strains of Lactobacillus, Lactobacillus plantarum Lp529 had excellent performance in all aspects. Therefore, it was selected as a potential strain of cholesterol-lowering probiotics and followed up with a commercial strain, Lactobacillus plantarum LpOnlly. The study of the BSH activity of Lp529 and LpOnlly showed the following characteristics: 1) the activity of BSH was not activated or inhibited by its substrate and substrates, which showed the character of BSH non-metamorphic enzyme. 2) the total enzyme activity accumulation curve of BSH was S-shaped, similar to the growth curve of strain, and the specific enzyme activity of BSH increased rapidly during the logarithmic growth period of the strain, then decreased slightly before the plateau stage and kept stable. 3) simulating the short time reversible regulation of BSH activity in human bile. 4) the two strains were subcultured and acclimated in simulated human bile. The results showed that the BSH activity was lower than the enzyme activity generation by generation, and reached the lowest value after the fourth generation, which was only 60% of the initial value, and the ability of lowering cholesterol was also decreased, and the tolerance of bile salt was gradually increased. 5) finally, the mechanism of cholesterol lowering by Lactobacillus was discussed and verified by introducing the BSH total enzyme activity-cholesterol coprecipitation curve, which provided theoretical support for the screening of the aforementioned excellent strains. It was confirmed that cholesterol reduction in vitro was the result of co-precipitation and assimilation. In the cholesterol removal effect of 6 strains, the assimilation was stronger than coprecipitation.
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2008
【分類(lèi)號(hào)】：R371

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