Abstract

Exopolysaccharides synthesized by lactic acid bacteria play a major role in the manufacturing of fermented dairy products as thickening agents. Exploration of the biodiversity of wild lactic acid bacteria from natural environments is currently the most suitable approach to search for the desired exopolysaccharide-phenotype. A total of 82 thermophilic lactic acid bacteria strains were isolated from Algerian raw camel milk. The isolation of strains was carried on modified Chalmers agar medium, under semi anaerobic conditions at 42°C. Bacterial isolates were phenotypically characterized and grouped into four genera: Lactobacillus (31.7%), Enterococcus (30.5%), Streptococcus (24.4%) and Pediococcus (13.4%). Based on the mucous type of the colonies, thirty EPS-positive strains were selected to be screened for their ability to produce exopolysaccharides. The production of polymers was carried out on Man, Rogosa and Sharpe (MRS) broth, supplemented with lactose and glucose as carbon sources. Yields quantification of soluble exopolysaccharides using a colorimetric method, showed that the selected strains produce yields ranging between 160 and 740 mg/l for Lactobacillus strains, between 126 and 319 mg/l for Streptococcus strains, between 70 and 242 mg/l for Enterococcus strains and between 132 and 134 mg/l for Pediococcus strains. This suggests that some strains have potential to be used as new culture starters for this and possibility other dairy products.

Key words: Camel milk, thermophilic lactic acid bacteria, exopolysaccharides.

Abbreviation

EPS, Exopolysaccharides; LAB, lactic acid bacteria; TLAB, thermophilic lactic acid bacteria; OD, optical density; BSA, bovine serum albumin