Isolation and molecular identification of exopolysaccharide producing lactic acid bacteria from sheep milk and yogurt

Dairy products can be a rich source of diverse lactic acid bacteria (LAB) with high functional properties, such as exopolysaccharide (EPS) production. EPS are high molecular weight polymers that are composed of sugar units and are secreted by microorganisms into the surrounding environment. Produced EPS can be used as an additive by a health effect and texturing properties. In this study, exopolysaccharide producing LAB (ropy and mucoid colonies) were isolated and identified from raw sheep milk and sheep yogurt that made in rural areas of Urmia. For this purpose, lactic acid bacteria cultured on MRS agar and M17 agar media and then isolated on the basis of the ability to produce exopolysaccharides to study the diversity of species by phenotypic methods (Gram stain, biochemical and physiological tests) and then identified by polymerase chain reaction (PCR). The 4 strains of LAB isolated were Gram-positive as well as catalase negative and were able to produce large amounts of EPS. The amounts of bonded and abandoned exopolysaccharides which measured by phenol/sulfuric acid method, were 40.28±0.2 to 65.26±0.47 mg/L and 105.68±3.2 to 136.35±0.2 mg/L, respectively. Sheep yogurt which manufactured traditionally in West Azerbaijan province, contained exopolysaccharide producing strains that can have the potential to use in the dairy industry.