Antifungal activity of lactic acid bacteria isolated from kunu-zaki, a cereal-based Nigerian fermented beverage

Fungal deterioration is a barrier to the wide acceptance of fermented cereal foods from Africa. The use of pro-tective cultures is a natural approach to controlling fungi in foods that also complies with a clean label strategy. This study aims to select antifungal lactic acid bacteria (LAB) previously isolated from kunu-zaki to bio-control deterioration in this cereal-based Nigerian fermented beverage. Strains of Leuconostoc citreum (1), Limosilacto-bacillus fermentum (6), and Weissella confusa (3) were the most active against seven test mold species, with average inhibition score of 2.25-2.88, after screening 220 LAB strains using agar overlay on millet-sorghum flour hydrolysate (MSFH) agar. The MSFH agar diffusion method revealed that antifungal activity against the seven target molds was retained in cell-free supernatants (CFSs) of selected LABs, with the strongest inhibition against A. flavus F008BA and P. citrinum 3AS1 demonstrated by L. fermentum 5KJEU5 (9.06%) and W. confusa YKDIA1 (24.55%), respectively. The antifungal activity of CFSs was mainly due to the occurrence of acidic compounds, with the most abundant compounds being acetic (0.30-1.96 mg/mL) and lactic (1.80-3.23 mg/mL) acids. Other compounds such as hydroxycaffeic (0.16-6.72 mu g/mL), 3-(4-hydroxyphenyl) propionic (1.40-6.36 mu g/mL), 3-phenyllactic (1.28-24.48 mu g/mL), and hydroxyferulic acids (12.25 mu g/mL) occurred at lower concentrations. In challenged kunu-zaki, L. fermentum 5KJEU5 prevented the growth of A. flavus F008BA and P. citrinum 3AS1 beyond 8 day at ambient temperature (25 C). In this study, LAB from kunu-zaki displayed strong antifungal activity, showing great potential as a protective culture to prevent fungal growth and mycotoxin accumulation in cereal foods.