ASSESSMENT OF ANTAGONISTIC POTENTIAL OF PROBIOTIC LACTIC ACID BACTERIA AGAINST AFLATOXIGENIC MOULDS IN MAIZE

Abstract

The contamination of maize with moulds, poses a significant threat to food safety and human health due to the presence of mycotoxins. The aim of this research was to assess the biocontrol ability of probiotic lactic acid bacteria (LAB) against mycotoxigenic moulds isolated from maize. Maize samples were purchased from local grain stores within Samaru Market, while soybean curd (wara) samples were purchased from selling points at Ahmadu Bello University (ABU) Main Campus. Part of both samples were analysed for proximate composition at the Institute of Agricultural Research (IAR), ABU, Zaria, while the remaining parts were processed in the laboratory of the Department of Microbiology ABU Zaria using standard microbiological procedures. Potato Dextrose Agar (PDA) was used as a medium to isolate the fungi, identified by microscopy and screened for aflatoxin production by ultraviolet (UV) light at wavelength of 290nm. The soybean curd was cultured on De Man Rogosa and Sharpe Agar (MRS) for isolation of LAB following manufacturer’s instructions, observed for morphological and biochemical characteristics and screened for probiotic characteristics. Antagonistic activities of probiotic LAB isolates were tested against the aflatoxigenic moulds using overlay method. Proximate analysis results showed that maize samples contained moisture (7.40% - 7.60%), Ash (1.00% - 1.10%), lipid (6.00% - 6.40%), protein (8.20% - 8.34%), fibre (2.33% - 2.40%) and carbohydrate (76.76% - 77.10%), while soybean curds were found to contain moisture (30.04%-30.35%), ash (2.7% - 2.85%), lipid (22.59% - 23.50%), protein (40.66% - 40.84%), fibre (1.67% - 1.70%) and carbohydrate (76.76% - 77.10%). Five (5) out of the six (6) moulds isolated from maize sample were found to be Aspergillus flavus, while one Aspergillus niger was isolated. All five A. flavus were confirmed as aflatoxigenic by UV screening, while A. niger was not. LAB isolated from three samples of soybean curd were all confirmed to be Lactobacillus species, which were further confirmed to be probiotic. Only one of the LAB isolates was found to have antagonistic activity against the mycotoxigenic moulds after 3days, 5days and 7days respectively. It is concluded from this research that that the probiotic lactic acid bacteria isolates have potential use as biocontrol agents against aflatoxigenic moulds, and may be further explored for possible solution to the problem of aflatoxin contamination in maize.

Key words: antagonistic activity; probiotic; lactic acid bacteria; aflatoxigenic; maize; biocontrol