MALDI-TOF MS profiling and antifungal activity of lactic acid bacteria from kunu aya, a tiger nut traditional beverage of Nigeria

The application of matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) as a technique for high-throughput characterization of microbiota in African traditional foods is limited. Kunu aya is an unexplored reservoir of protective lactic acid bacteria (LAB) strains. A total of 26 LAB isolates from kunu aya were identified using MALDI-TOF MS as five species, including Lactiplantibacillus plantarum (14), Pediococcus pentosaceus (9), Levilactobacillus brevis (1), Lactiplantibacillus pentosus (1), and Weissella paramesenteroides (1). Antifungal activity screening of all LAB strains by agar-plate overlay assay revealed inhibition against Penicillium crustosum FOO5BA and/or Aspergillus flavus FOO8BA by six strains: L. plantarum (3), Pd. pentosaceus (1), L. brevis (1), and W. paramesenteroides (1). The six LAB strains demonstrated broad spectrum antifungal activity, when tested against eight molds from plant-based foods, inhibiting 4 to 7 molds, with average inhibition scores (AIS) of 0.75–2.75. L. brevis MKAIA1b showed the strongest antifungal activity (AIS; 2.75). Agar diffusion method revealed that antifungal activity against all target molds was retained in cell-free supernatants of L. brevis MKAIA1b, with the highest inhibition demonstrated against P. citrinum 3AS1 (15.34%). In challenged kunu aya fermented with L. brevis MKAIA1b or L. brevis MKAIA1b and L. plantarum TMP051, the growth of A. flavus F008BA, Fusarium langesthiae 13,014, and P. crustosum FOO5BA was delayed beyond 7 days at ambient temperature (25 °C). In this study, MALDI-TOF MS was an effective tool to reveal the species composition of LAB in kunu aya, which harbors LAB strains that displayed strong antifungal activity, while showing great potentials as a protective culture and for bio-control.