Screening and identification of extracellular polysaccharide-producing lactic acid bacteria

Abstract

Objective: To screen lactic acid bacteria strains with strong ability to produce extracellular polysaccharide. Methods: Forty strains of lactic acid bacteria isolated and preserved in the laboratory were selected, and the commercial strain L. rhamnosus GG （LGG） was used as the positive control strain. The strains with high extracellular polysaccharide yield were screened by colony drawing method and phenol-sulfuric acid method, and their stress resistance, safety and antibiotic sensitivity were tested in vitro. The phenotypic characteristics and species identification of the finally obtained strains were analyzed. Results: After primary screening and secondary screening of 40 strains of lactic acid bacteria, 10 strains of lactic acid bacteria with high extracellular polysaccharide production were obtained. After comprehensive evaluation of polysaccharide production, stress resistance and preliminary safety of the 10 strains of lactic acid bacteria, 4 strains of lactic acid bacteria with high EPS production were finally isolated and identified, namely, 2 strains of lactobacillus paracasei （LZ9089, LZ9Y10）, 1 strains of Lactobacillus casei （LZ9183） and 1 strains of Lactobacillus brevis （LZ9285）. Conclusion: Four strains with high exopolysaccharide yield have good basic probiotic characteristics and have potential development and utilization value.

Keywords

• exopolysaccharides
• lactic acid bacteria
• sift
• identification
• probiotic function