Abstract:
Twenty-eight strains of lactic acid bacteria from five fermented food samples
namely: “burong kanin” (BK), “burong isda” (BI), “balao-balao” (BB), “longganisa”
from Ilocos region (LI), and “longganisa” from Cavite (LC) were screened and tested for
antimicrobial activity using the agar well diffusion assay method and Lactobacillus
plantarum NCDO 955 as indicator microorganism. Strain 3 isolated from “burong
kanin” (BK3) exhibited the highest antimicrobial activity. BK3 isolate strain grew best in
de Man, Rogosa, and Sharpe (MRS) medium than in Tryptone Glucose Yeast Extract
(TGYE) medium. Two samples (crude and semi-purified extracts) were used in the
elucidation of antimicrobial factors: organic acids, enzymes, hydrogen peroxides and
bacteriocins. | The semi-purified sample was prepared by pH-mediated adsorption desorption
method followed by dialysis, high-speed centrifugation and lyophilization
(freeze-drying). Antagonistic activity from the crude sample manifested inhibitory
effects due to production of lactic acids, and probably due to peroxides and enzymes. On
the other hand, the semi-purified or freeze-dried sample showed inhibitory effects on the
growth of Lactobacillus brevis, Lactobacillus lactis subsp. lactis and Lactobacillus
plantarum NCDO 955 which was suggestive of bacteriocin activity. The zone of
inhibition was largest at pH 2. The antimicrobial activity of BK3 isolate at neutral pH
was probably an indication of bacteriocin action. Bactericidal activity was lost at high
pH values especially when high pH values were combined with an elevated temperature.
BK3 isolate was not affected by amylases but was destroyed by exposure to a proteolytic
enzyme. The BK3 strain from “burong kanin” was found to be Gram-positive which
inhibited the growth of Lactobacillus lactis while no inhibition was observed against
Escherichia coli.
