乳酸菌吸附苯并芘特性评价及机制研究

Lactic acid bacteria (LAB), as the most important probiotic microorganisms which have beneficial health effects when ingested by humans, have been widely used in food industry. Numerous researches have revealed that LAB cells show definite ability to bind myco-toxins and hetercyclic aromatic amines which cause potentially cancer. However, few investigations linked to the binding properties of LAB cells towards Benzo(a)pyrene (BaP) have been carried out. The objectives of this study are to investigate the roles of LAB cells in removing BaP from their surroundings. Firstly, LAB strains are co-cultured with BaP, and the percentages of these strains to bind BaP are analyzed. Next, a rapid method to screen high BaP-binding strains are developed in terms of the relationship between binding ability and the properties of cell aggregation or bacterial suspension. Meanwhile, physical and chemical factors which affect the binding effects of the LAB strains to BaP are evaluated to investigate the mechanism of this process and clarify the binding site. The effects of BaP on the growth metabolism of the LAB strains also are observed at the proteomics and transcriptomics levels. Finally, the in vivo efficiency of the LAB strains to remove BaP is examined by analyzing DNA damage and the expression level of p53 and Bcl-2 genes in an established rat model. This present work will provide definite theory basis for the use of LAB as a biological detoxification agent to remove BaP from dietary and relevant environments.

乳酸菌是一类重要的益生菌，在食品工业中应用广泛。尽管已有研究报道证实，乳酸菌能够吸附脱除真菌毒素以及杂环胺类等致癌物，但关于乳酸菌吸附去除苯并芘的研究报道甚少。本研究以乳酸菌为研究材料，采用菌体与苯并芘共培养的方法，检测各菌株吸附苯并芘的能力，通过比较吸附能力与菌体及菌悬液特性参数之间的关系，建立高吸附菌株的快速筛选方法。通过分析不同理化因素对乳酸菌吸附苯并芘特性的影响及细胞各组分的吸附能力，明确吸附机制，确定吸附位点。利用蛋白质组学和转录组学技术，研究苯并芘对乳酸菌生长代谢的影响，阐明吸附与代谢的关系。借助小鼠模型，通过检测DNA损伤情况、p53基因及Bcl-2基因表达水平，评价乳酸菌脱除苯并芘的效果，旨在为利用乳酸菌在食品及相关环境中生物脱除苯并芘提供理论依据。

苯并芘（benzopyrene）广泛存在于环境中, 是一种高活性的致癌物和诱变剂。乳酸菌是食品工业中重要的益生菌，已证实其能够吸附脱除真菌毒素以及杂环胺类等致癌物，但关于乳酸菌吸附去除苯并芘的研究报道甚少。本研究以乳酸菌为研究材料，采用菌体与苯并芘共培养的方法，检测各菌株吸附苯并芘的能力，共计评价了82株食源性乳酸菌的苯并芘脱除能力，从中筛选出具有较高苯并芘吸附率的菌株5株，包括植物乳杆菌（Lactobacillus plantarum）、戊糖乳杆菌（Lactobacillus pentosus）、乳双歧杆菌（Bifidobacterium lactis）和婴儿双歧杆菌（Bifidobacterium infantis）等。进一步分析了不同理化因素对乳酸菌吸附苯并芘特性的影响及细胞各组分的吸附能力，明确了吸附机制，确定了细胞壁肽聚糖是菌株吸附苯并芘的主要位点。使用Materials Studio软件构造肽聚糖结构模型，利用分子对接原理和分子动力学方法模拟并分析菌体吸附苯并芘的过程。为探究在体内环境下乳酸菌能否有效缓解苯并芘致机体的毒性，本研究选择对苯并芘吸附效果较好的植物乳杆菌菌株121为测试菌株，经28天经口染毒实验建立小鼠模型。结果表明，乳杆菌菌株能加快苯并芘随粪便排出的速度和排出量，减少由苯并芘导致的肠道乙酸、丙酸含量的减少，减缓由苯并芘导致致的小鼠血细胞DNA损伤，说明菌株在体内具有一定缓解苯并芘毒性的效果。本项目研究结果可为利用乳酸菌在食品及相关环境中生物脱除苯并芘提供理论依据。