Probiotic Characterization of Bacteriocinogenic Lactic Acid Bacteria Isolated from Fermented Foods of Selected Areas in Central Luzon

Abstract

One hundred sixty putative isolates of lactic acid bacteria (LAB), obtained from nineteen fermented foods purchased from public markets in Central Luzon, were screened for bacteriocin production. Boiled and pH-neutralized culture supernatants of the LAB isolates were spotted on to agar plates using Listeria monocytogenes 3 (Lm 3) or Enterococcus faecium 79 (Ef 79) as indicator microorganisms. Thirty-two LAB isolates showed bacteriocin activities, eight of which with high activity against Lm 3 (> 6,400 AU/ml) and good activity against Ef 79 (> 1,600 AU/ml). The nature of bacteriocin- encoding genes was determined through polymerase chain reaction (PCR) assay using primers for pediocin, plantaricin, nisin and lactococcin. The template DNA were aqueous extracts from cells of LAB isolates added with HPLC water and treated in boiling water bath for ten minutes. Results showed that five were positive for the pediocin gene and two for the plantaricin gene. None encoded for lactococcin and nisin gene. It was presumed that the remaining bacteriocinogenic LAB carried some other types of bacteriocin-encoding genes. Two high bacteriocin-producing LAB isolates, namely strains 3G3 and 4B1, were selected and tested for acid and bile resistance. They were identified as Lactobacillus pentosus and Lactobacillus, fermentum using API 50 CPIL ID kit, respectively. Both strains were relatively stable upon exposure for three hours to pH 3 artificial gastric juice (AGJ) with 0.2% pepsin. At pH 2, both gave more than 60% viability after three hours in AGJ. Further incubation for three hours in simulated intestinal fluid (SIF), containing 0.3% Oxgall (bile), gave 45% and 72% viability for 3G3 and 4B1, respectively. Lb. fermentum 4B1 had both good acid and bile tolerance as compared to reference strain 1Y9, which was previously isolated from a probiotic drink Yakult® by Kisworo (2006). This particular LAB has very good probiotic potential with added high bacteriocin production, properties that are very attractive in the development of new probiotic food and drinks.