Inhibitory Properties of Lactic Acid Bacteria against Moulds Associated with Spoilage of Bakery Products

Abstract

Aim: To evaluate the potentiality of LAB strains isolated from different fermented products to inhibit moulds associated with spoilage of bakery products. Methodology: Lactic acid bacterial (LAB) strains obtained from fermented products (“burukutu”, “pito”, yoghurt, and “iru”) were screened for antifungal activity against moulds (Aspergillus flavus, Aspergillus fumigatus, Aspergillus repens and Penicillium sp.) isolated from spoilt bakery products. Inhibitory activities of the lactic acid bacterial isolates were determined by the dual agar overlay method and well diffusion method. Results: Eleven isolates (79%) out of the fourteen lactic acid bacterial strains screened showed antifungal activity against one or more of the moulds when the method used was dual agar overlay method. When agar well diffusion assay was used to check the antifungal activity of the cell-free culture supernatants of these eleven LAB isolates after excluding inhibition due to organic acids and hydrogen peroxide, only four LAB strains (BE1, IO1, PO4 and PO9) continued to show antifungal activity against the moulds. The selected bacteriocin-producing LAB strains (BE1, IO1, PO4, and PO9) were identified as Lactobacillus cellobiosus, Pediococcus pentosaceus, Lactobacillus rhamnosus, and Tetragenococcus halophilus respectively using API 50 CHL system. The cell-free culture supernatant of P. pentosaceus IO1, T. halophilus PO9, and L. cellobiosus BE1 sprayed on bread surface inhibited the growing of moulds during 14 days of storage in polythene bags. Conclusion: These LAB isolates from fermented products capable of inhibiting the moulds have potential that could be used as biopreservative agents in bakery products.