MALDI-TOF MS profiling and exopolysaccharide production properties of lactic acid bacteria from Kunu-zaki - A cereal-based Nigerian fermented beverage.

MALDI-TOF MS is a technique for high-throughput characterization of foodborne microbiota, however, its application for studying African traditional fermented foods is limited. A total of 164 out of 220 lactic acid bacterial (LAB) isolates from Kunu-zaki were identified using MALDI-TOF MS, with 100% identity of representative strains compared to 16S rRNA gene sequencing. MALDI-TOF MS profiling combined with 16S rRNA gene sequencing revealed a total of 15 LAB species in Kunu-zaki, where the most predominant species were Lactiplantibacillus plantarum (40.46%), Weissella confusa (27.27%), and Pediococcus pentosaceus (15.00%). Phenotypic screening of all isolates revealed strains of W. confusa (57), Lactiplantibacillus sp. (9), Companilactobacillus musae (1), Ligilactobacillus saerimneri (1) and Leuconostoc citreum (1) that are capable of producing dextran and/or fructan. Dextransucrase genes were detected in all EPS-producing strains by PCR. Weissella confusa YKDIA1 and YKDIA4 produced 11.93 and 11.70 g/L dextran from millet-sorghum flour hydrolysate-sucrose, respectively. Kunu-zaki produced using W. confusa YKDIA1 had high water holding capacity (100%) and viscosity ranging from 49.46-139.24 mPas. In this study, MALDI-TOF MS adequately revealed the LAB species composition in Kunu-zaki in a high-throughput strategy and further, the dominant occurrence of EPS-producing LAB strains and their potentials to influence the rheological properties of Kunu-zaki were demonstrated.

Production and characterization of volatile compounds and phytase from potentially probiotic yeasts isolated from traditional fermented cereal foods in Nigeria.

BACKGROUND: Probiotic strains are incorporated into food substrates to contribute to fermentation process. The technological suitability of such strains to improve the flavor and nutritional value of fermented food is strain-specific. Potentially probiotic yeasts isolated from Nigerian traditional fermented foods were assessed for production of volatile compounds by gas chromatography-mass spectrophotometry. Phytases were characterized for activity and stability at different pH (3-8) and temperatures (25-50 °C). RESULTS: A total of 45 volatiles compounds were identified from intracellular cell-free extracts of Pichia kluyveri LKC17, Issatchenkia orientalis OSL11, P. kudriavzevii OG32, P. kudriavzevii ROM11, and Candida tropicalis BOM21. They include alcohols (14), carbonyls (13), esters (10), and organic acids (8). Phenylethyl alcohol was the highest higher-alcohol in Issatchenkia orientalis OSL11 (27.51 %). The largest proportion of esters was detected in P. kudriavzevii OG32 (17.38 %). Pichia kudriavzevii OG32 and C. tropicalis BOM21 showed vigorous gowth in minimal medium supplemented with sodium phytate (2 g L-1). Extracellular phytases from P. kudriavzevii OG32 and Candida tropicalis BOM2 showed optimal activiy at pH 4.6 (104.28 U) and pH 3.6 (81.43 U) respectively. CONCLUSIONS: Results obtained revealed species- and strain-specific potentials of the yeast strains to improve flavor and mineral bioavailability of fermented food products. Therefore, the application of these yeasts as starter cultures during food fermentation process is a very promising method to enhance the flavor profile and enhance mineral bioavailability in indigenous cereal-based fermented food products.