Effect of Cultural Conditions and Media on the Antimicrobial Activity of Streptococcus Thermophilus

Abstract

ABSTRACT When Streptococcus thermophilus was grown in basal medium with or without fermentable carbohydrate (lactose, glucose or sucrose at 2% level), antimicrobial activity was detected only in the cell‐free medium and cells were free of any antimicrobial activity. Peanut milk, soymilk and basal medium with a fermentable sugar supported the production of antimicrobial compound(s) by S. thermophilus. Milk‐based medium did not appear to be a necessity for such activity. When tested independently, the optimum temperature for maximum production of antimocrobial activity by S. thermophilus in whole milk was 50°C while the optimum time of incubation was 48 hr. An initial pH of 6.0 resulted in maximum antimicrobial activity in basal medium with 2% lactose.