Abstract

Rowaida K. Khali

The purpose of this research was to evaluate the probiotic potential of a capsulated Streptococcus thermophilus CHCC 3534 strain. The strain proved to tolerate 0.4% oxgall and was sufficiently resistant to pH as low as 2.5 for 3 h of exposure. The strain demonstrated high adherence to human intestinal mucus, and showed a unique resistance to different antibiotics. Crude extracts of S. 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 -amylase and lipase. SDS-PAGE analysis of the partially purified bacteriocin revealed one peptide with a molecular weight ranging from 14.4 to 18.4 kDa. The strain may have an industrial significance and represents an interesting candidate for use in food biopreservation, probiotic formulations and in the control of spoilage caused by foodborne pathogens.