分离自传统自然发酵食品中降胆固醇乳酸菌的筛选与评价

The Screening and Evaluation of Cholesterol-lowering Lactic Acid Bacteria Isolated from Traditional Naturally Fermented Food

为了筛选优良的降胆固醇乳酸菌,本分析了从传统自然发酵食品中分离的30株乳酸菌,从中筛选出WS1、LP2、LP3、LP4、LP5和LP66株具有较强降胆固醇能力的乳酸菌,并通过对其胆盐耐受性及在含胆盐MRS培养基中的降胆固醇效率的分析,复筛出其中的WS1、LP2、LP3和LP64株乳酸菌。对4株乳酸菌的生长特征、产酸特征、不同生长阶段的种子液对胆固醇的降低效率的影响、耐酸特征及人工胃酸的耐受性进行分析和评价。结果显示,4株优选的乳酸菌降胆固醇能力较好,在胆盐中具有一定的存活力。胆盐的存在对降胆固醇能力具有一定的促进作用,4株菌在常规MRS培养基中生长和产酸特征稳定。不同生长时期的种子液对乳酸菌的降胆固醇能力有一定影响,对数期优于稳定期。耐酸性分析表明,pH越高,乳酸菌耐受性越好。pH2.5,处理2h,乳酸菌依然具有一定的存活力;pH3.5,乳酸菌存活力和存活时间都有所提高,pH4.5时的存活力基本和自然pH的保持一致。在人工胃酸条件下,4株复筛乳酸菌在pH2的条件下,存活时间超过4h,随着pH的升高,存活率和存活时间都有所提高。本试验结果表明,4株乳酸菌均具有降胆固醇的特征,为后续优良菌株的降胆固醇机理研究打下了基础。

The aim of this study was to screen out good cholesterol-lowering lactic acid bacteria. 6 strains of lactic acid bacteria, WS1, LP2, LP3, LP4, LP5 and LP6, which showed stronger cholesterol-lowering ability, were selected out from 30 strains of lactic acid bacteria isolated from traditional naturally fermented food. The tolerance of the 6 strains was analyzed and their cholesterol-degrading efficiency and effectiveness were detected in MRS medium with bile salt. Following this, 4 strains, WS1, LP2, LP3 and LP6 were further sieved out. It was analyzed and evaluated for the 4 strains lactic acid bacteria about their growth curves, acid-yield feature, effect of seed from different growth stage on cholesterol-lowering ability and resistance in simulated gastric acid. The results showed that cholesterol-lowering ability of the 4 strains was very nice and could survive in certainly concentration bile salt. The cholesterol-lowering ability was promoted with the presence of bile salt. The growth curve and acid yield feature of 4 strains were stable in normal MRS medium. The cholesterol-degrading ability was different between the seed from different growth phases, the seed from log phase better than that from stable phase. In this study, the result of acid tolerance showed that the resistance of these lactic acid bacteria was stronger when pH was higher. With the pH going higher, the viability increased. Their growth hardly showed difference between pH 4.5 and normal pH. 4 strains could survived 4 h in artificial gastric acid with pH 2 and the viable rate and time extended with the increase of pH. The results implied that the 4 strains could be used in manufacture which needed cholesterol-lowering lactic acid bacteria as starter. It also laid foundation for the further research on cholesterol -lowering mechanism of the 4 strains lactic acid bacteria.