Antimicrobial activity of lactic acid bacteria against pathogenic and spoilage microorganism isolated from food and their control in wheat bread

The evaluation of antimicrobial activities of Lactobacillus sakei KTU05-6, Pediococcus acidilactici KTU05-7, Pediococcus pentosaceus KTU05-8, KTU05-9 and KTU05-10 strains producing organic acids and bacteriocins like inhibitory substances (BLIS) against undesirable microorganisms in the food industry, were performed using an agar well diffusion assay method. The metabolites of lactic acid bacteria (LAB) inhibited the growth of pathogenic bacteria, belonging to Bacillus, Pseudomonas, Listeria and Escherichia genera in various degrees. The organic acids and BLIS of LAB show fungicidal and fungistatic activities against fungi and yeast such as Fusarium culmorum, Penicillium chrysogenum, Aspergillus fumigatus, Aspergillus versicolor, Penicillium expansum, Aspergillus niger, Debaryomyces hansenii and Candida parapsilosis. 20% of P. pentosaceus KTU05-9 sourdough in a bread recipe suppressed the bread ropiness in artificially contaminated bread by Bacillus subtilis spores, until 6 days storage at 23 °C. Moreover P. acidilactici KTU05-7, P. pentosaceus KTU05-8 and KTU05-10 single cell suspension sprayed on the bread surface, inhibited growing of fungi until 8 days of storage in polythene bags. The presence of BLIS and organic acids by tested LAB is an indication that these bacteria can be used widely in the food industry as bio-preservatives due to their broad inhibition spectrum.

► We examined antimicrobial activity of lactic acid bacteria. ► We examined antimicrobial activity of bacteriocin like inhibitory substances. ► Pediococcus pentosaceus suppressed the bread ropiness in artificially contaminated bread. ► Lactic acid bacteria suppressed the bread moulding until eight days.