LAUSR

Abstract There is always interest in investigating new lactic acid bacteria strains for product development that can complement or replace currently-in-use starters. This study screened native strains of Streptococcus thermophilus from various plant/dairy sources across India and compared them with commercial yoghurt starters. A total of 158 isolates were characterised as S. thermophilus by polyphasic approach and strain typed using (GTG)5 primers by repetitive sequence-based polymerase chain reaction. After cluster analysis, 12 major clusters were defined at a similarity level of 70%. They were evaluated for functionally important metabolic traits and representative genotypes with desired starter activity were used for yoghurt production along with commercial starter. Based on physico-chemical attributes, sensory and principal component analysis, yoghurt prepared using representative plant and dairy isolates were indistinguishable from product prepared using reference yoghurt strains. The identified strains were promising with additional functional attributes such as galactose fermenting ability and negative for urease activity.