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Title: Inhibition Activity of Lactic Acid Bacteria Isolated from Fermented Foods against Vegetative Cells and Spore Germination of Bacillus Spp.
Authors: Wasim S. M. Qadi
Keywords: spore germination
antimicrobial activity
Bacillus cereus
B. subtilis
B. spizizenii
lactic acid bacteria
Issue Date: Jul-2017
Publisher: Universiti Sains Islam Malaysia
Abstract: Bacillus spp.are endospore-forming, Gram-positive bacteria able to cause food spoilage and foodborne diseases. Lactic acid bacteria (LAB) are known for their ability to synthesize compounds that can inhibit growth of vegetative cells and spore germination of Bacillus spp. The aim of this study was to screen LAB isolated from yogurt, fermented shrimp paste “belacan” and fermented durian “tempoyak” for antimicrobial activity on vegetative cell growth and spore germination of Bacillus cereus, B subtilis and B.spizizenii. Results of agar spot assay showed that from the 45 LAB cells 98% inhibited strongly growth of B.cereus compared to 78% against B.spizizenii and 51% against B.subtilis. The LAB supernatant showed strong inhibitory activity against B.cereus 58%,followed by B. spizizenii 44.5% and B.subtilis 31%. Variable inhibitory activity against vegetative cells and spore germination was observed when he pH of supernatants was adjusted to Ph 4,5 and 6.The supernatants of all LAB isolates showed good inhibitory activity against vegetative cells 46.5% against B.cereus, 31% against B.subtilis and 37.8% against B.spizizenii at Ph 4. LAB isolated from belacan and fermented durian showed activity at Ph 5 and 6: 15.5% against B.subtilis, 20% against B.cereus and 2% against B. spizizenii. Sepernatant of LAB from yogurt lost its inhibitory activity at pH 5 and 6.Spore germination of the Bacillus spp. Was affected by LAB cells and supernatants. LAB cells isolated from yogurt, belacan and fermented durian inhibited strongly spore germination of B. subtilis (89%) than B. cereus (73.3%) as evaluated by spot assay. In contrast, the supernatant demonstrated variable inhibitory activity against spore germination as indicated by 24.4% for B. subtilis, 29% for B. cereus and 15.5% against B.spizizenii as evaluated by well method. Spore germination was strongly inhibited by pH of supernatant, greater inhibition at pH 4 compared to pH 5 and 6.The supernatant of LAB isolates from belacan and durian inhibited spore germination at pH 5 and 6. While Supernatant of LAB from yogurt lost its inhibitory activity against spore germination at pH 5 and 6. Antimicrobial activity of supernatant LAB (BP2, BK4, BT1, D2) were diminished when treated with proteinase k, RNase I. LAB isolates from “belacan” and fermented durian were susceptible to Penicillin G (PI), Gentamicin (CN), Chloramphenicol (C), Tetracycline (TE) but resistant to vancomycin and Streptomycin (S). This study indicated that the presence of compounds in LAB supernatants that have inhibitory activity against vegetative cells and spore germination at pH 5 and 6. Such compounds may have potential use for food biopresevation against food spoilage and foodborne disease caused by Bacillus spp.
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