产胞外多糖乳杆菌的菌种鉴定及其发酵条件优化

Screening and identification of lactobacillus with exopolysaccharideproducing capacity and optimization of culture conditions

采用苯酚-硫酸法从45株乳酸菌中筛选得到1株产胞外多糖的乳酸菌NM18,对其进行形态特征观察为杆状细菌,通过16S rDNA基因序列分析对该菌株进行了菌种鉴定,PCR扩增得到1478 bp序列,PCR产物序列通过Blast软件在NCBI网站中进行同源性比较,通过MEGA 5.0软件绘制系统发育树,菌株NM18鉴定为植物乳杆菌。通过单因素试验和正交试验确定其最佳发酵条件:初始pH值6.5、发酵温度37℃、发酵时间34 h、最佳接种量1.5%,此条件下菌株NM18的胞外多糖合成量为206.8 mg/L,与基础培养基相比胞外多糖合成量提高15.2%。

Using phenol-sulfuric acid method screened a exopolysaccharide-producing strain NM18 from 45 strains of lactic acid bacteria. Based on 16 S rDNA sequence analysis in a 1478 bp PCR amplification sequence, strain NM18 was primarily identified as Lactobacillus plantarum, homology comparison with NCBI databases using the software Blast and phylogenetic tree construction using the software MEGA 5.0. By single factor test and orthogonal test to determine the optimum conditions for the initial pH 6.5, fermentation temperature is 37 ℃, fermentation time was 34 h, optimal inculum quantity was 1.5%, Under this conditions, the production of exopolysaccharides reached 206.8 mg/L, the synthesis amount increased by 15.2%.