Evidence for probiotic potential of a capsular-producing Streptococcus thermophilus CHCC 3534 strain.

The purpose of this research was to evaluate the probiotic potential of an capsulated Streptococcus thermophilus CHCC 3534 strain. The strain tolerates 0.4% oxgall (bile) and was sufficiently resistant to pH as low as 2.5 for 3 hours of exposure. The strain demonstrated high adherence to human intestinal mucus, and showed unique resistance to different antibiotics. Crude extracts ofS. thermophilus CHCC 3534 contained a diffusible antimicrobial compound "bacteriocin" with a broad spectrum that inhibited the growth of closely related lactic acid bacteria and a number of food spoilage bacteria including Salmonella typhimurium and Staphylococcus aureus. The bacteriocin was heat stable, resistant to pH, inactivated by proteolytic enzymes, and resistant to a-amylase and lipase. A SDS-PAGE analysis of the partially purified bacteriocin revealed one component with a molecular weight ranging from 14.4 to 18.4 kDa. The strain may have industrial significance and represents an interesting candidate for use in biopreservation, probiotic food formulations and in the control of spoilage caused by food borne pathogens.