乳酸菌胞外多糖产生菌的筛选与初步研究

Screening of and preliminary research on exopolysaccharides producing strain

目的从牧区传统乳制品中分离获得胞外多糖产量较高的菌株,并对胞外多糖的结构和功效进行初步研究,以期能为将来生产乳酸菌胞外多糖的可行性提供数据和依据。方法通过涂布平板法从内蒙古传统发酵乳制品中分离乳酸菌,并测定胞外多糖产出量,从中筛选胞外多糖高产菌株,通过生理生化试验和16S rRNA测序鉴定菌株。采用紫外光谱法和高效液相色谱法对胞外多糖的结构进行初步分析。通过测定胞外多糖的吸湿能力和保湿能力初步评价其吸湿保湿性能。结果共分离出90株菌株,筛选出1株胞外多糖高产菌株,并鉴定出该菌株为嗜热链球菌。通过分析得出该菌株产生的胞外多糖主要由4种单糖组成,分别为甘露糖、葡萄糖、半乳糖和阿拉伯糖,其摩尔比为0.25∶3.10∶3.70∶0.10,分子量范围为1.897×10~6~7.257×10~6 Da。通过保湿性能的测定,初步确定该嗜热链球菌产生的胞外多糖有良好的保湿性。结论本实验筛选出的胞外多糖高产菌株嗜热链球菌属于益生菌,有广泛的应用价值。

Objective To isolate strains with high exopolysaccharides yield from traditional dairy products in pastoral areas,and study the structure and efficacy of exopolysaccharides,so as to provide data and basis for the feasibility of producing lactobacillus exopolysaccharides in the future.Methods Lactic acid bacteria were isolated from traditional fermented milk from Inner Mongolia using spread plate technique.High-yield exopolysaccharides-producing strains were screened by comparing the yield of exopolysaccharides of each strain,and identified using biochemical tests and 16 S rRNA sequencing.Then the elementary structure of the exopolysaccharides was determined with ultraviolet spectroscopy and high performance liquid chromatography.The moisturizing property of the exopolysaccharides was evaluated by testing their properties of moisture absorption and moisture retention.Results Ninety strains were isolated in total and a strain with high-yield of exopolysaccharides was selected.The strain was identified as Streptococcus thermophilus afterwards.The exopolysaccharides it produced were mainly composed of mannose,glucose,galactose and arabinose,with a molar ratio of 0.25∶3.10∶3.70∶0.10,and a molecular weight range from 1.897×10~6 to 7.257×10~6 Da.Meanwhile,the exopolysaccharides had good moisturizing performance,similar to that of sodium hyaluronate.Conclusion Streptococcus thermophilus,a strain with high-yield exopolysaccharides-producing ability screened in this study,is a probiotics and has wide application value.