Identification and in vitro assessment of potential probiotic characteristics and antibacterial effects of subsp SKI19, a bacteriocinogenic strain isolated from Thai fermented pork sausage.

A total of 2257 lactic acid bacteria were preliminarily screened for antagonistic activity against subsp. JCM 1157. Strain SKI19 was selected and identified at the subspecies level as subsp. SKI19, using rRNA gene sequence analysis combined with and genes' amplification. Antibacterial activity of SKI19 was completely lost after treatment of neutralized cell free culture supernatant with proteolytic enzymes, suggesting that SKI19 produced a bacteriocin-like substance that inhibited not only closely related species, but was also effective against DMST 17303. Viewed under scanning electron microscope, cell membranes of the indicator strain appeared to collapse after exposure to the bacteriocin-like substance. In vitro tests concerning probiotic properties, SKI19 survived under simulated gastrointestinal tract conditions, and adhesion of its cell surface to xylene and chloroform was 90.14 and 89.85%, respectively. Complete inhibition by SKI19 against pathogenic bacteria ( DMST 4212, DMST 17303, and DMST 8840) was observed in co-cultivation under anaerobic conditions. A safety assessment showed that SKI19 was susceptible to several antibiotics and had no haemolytic activity. PCR amplification of virulence factors with the specific primers for , , , , , and genes were negative for SKI19. Also, SKI19 did not harbor any , , or genes involved in biogenic amine production. The results reveal that SKI19 has probiotic potential and antibacterial activity, and is safe for further application in certain food products.