人肠道乳酸片球菌的分离鉴定及其发酵枸杞汁性能分析

Isolation and Identification of Pediococcus lactis in Human Intestinal Tract and Its Performance Analysis of Fermented Goji Berry Juice

为获取定植能力强和枸杞汁发酵性能优良的候选菌株,从人肠道中分离筛选出3株乳酸菌。通过形态、生理生化、16S rDNA序列分析及系统发育树构建进行鉴定,并对其耐酸、耐胆盐、耐人工胃液、肠液及其发酵性能进行研究,研究其定植能力和发酵性能。结果表明,经鉴定3株均为乳酸片球菌(Pediococcus lactis),分别编号为NXU_220218、NXU_220219和NXU_220220。其中NXU_220218在2~8 h生长速度较快,产酸能力较强,对酸、胆盐、人工胃液的耐受能力均优于NXU_220219和NXU_220220,在pH为2时的存活率约为67%,在浓度为0.3%的牛胆盐中的存活率约为65%,对人工胃液的耐受能力为72%,人工肠液的耐受能力达到95%。将菌株NXU_220218接种于枸杞汁中发酵,经测定发现发酵枸杞汁中的还原糖含量显著降低,自由基清除率显著提高,表明其对枸杞汁具有良好的发酵性能,可作为乳酸菌的候选菌株应用于枸杞汁的发酵。

In order to obtain candidate strains with strong colonization ability and excellent fermentation performance of goji berry juice,3 strains of lactic acid bacteria were isolated and screened from human intestinal tract.They were identified by morphological,physiological and biochemical,16S rDNA sequence analysis and phylogenetic tree construction,and their acid resistance,bile salt resistance,artificial gastric fluid,intestinal fluid resistance and fermentation performance were studied.The results showed that all three strains were identified as Pediococcus lactis,numbered NXU_220218,NXU_220219 and NXU_220220,respectively.The growth rate from 2 to 8 h,the ability of NXU 220218 to produce acid was stronger,and the tolerance to acid,bile salt and artificial gastric juice was better than NXU 220219 and NXU 220220.The survival rate of NXU_220218 was 67%at pH2,65%in bovine bile salt at 0.3%concentration,72%tolerance to artificial gastric juice,and 95%tolerance to artificial intestinal juice.Finally,the NXU_220218 strain was inoculated and used in the preparation of fermented goji berry juice.It was found that the reducing sugar content and the free radical scavenging rate in the fermented goji berry juice were significantly reduced and increased,respectively,compared with the unfermented goji berry juice,indicating that the NXU_220218 strain had good fermentation performance for goji berry juice and could be used as a candidate strain of lactic acid bacteria for the fermentation of goji berry juice.