Investigation of some biotechnological properties of Streptococcus thermophilus strains isolated from human milk

In this study, PCR based genetic identification of five Streptococcus thermophilus strains isolated from milk taken from different volunteer mothers was performed. The antibiogram, hemolytic activity and gelatinase activities of the strains of S.thermophilus MAS were tested. In order to determine some biotechnological properties of S.thermophilus MAS strains, resistance to acid and bile, antimicrobial activity, aggregation properties, nisin resistance, antioxidant activity, sodium benzoate resistance, amylase, lichenase, protease and cellulase enzyme activities as well as hydrophobicity properties were investigated. All of the MAS strains were found to be amylase negative, lichenase positive, protease negative and MAS-3 strains were cellulase negative, MAS-1, MAS-2, MAS-4 and MAS-5 strains were positive for cellulase. None of the MAS strains showed antimicrobial activity against sixteen tested human to human pathogens. MAS-2 and MAS-3 strains inhibited fish pathogens V.anguillarium M1 and V.anguillarium A4 pathogens with inhibition zone varieted from 1.88mm to 3.34mm. In the determination of antioxidant activity, DPPH radical reduction activities of S.thermophilus MAS strains were recorded as 29.84-36.90% and iron ion chelating activities of S.thermophilus MAS strains were recorded as 23.44-30.13%.