Enzymatic and antimicrobial activities of lactic acid bacteria and yeasts isolated from boza, a traditional fermented grain based beverage

Grain-based fermented beverages have become very popular recently and are preferred by consumers globally owing to their several health benefits. This study focused on identification and characterization of lactic acid bacteria (LAB) and yeasts isolated from commercial boza samples with regards to their enzymatic (phytase activity, proteolytic activity, gluten degradation ability and phenolic acid decarboxylase enzyme activities) and antimicrobial properties. For this purpose, total 19 LAB and 5 yeast strains were identified from 12 boza samples collected from Turkiye market. LAB isolates showed high inhibitory effect on Salmonella Typhimurium ATCC 14028 and Listeria monocytogenes ATCC 13932. Majority of the isolates had varying gluten-degrading capabilities (13.09-25.77 mm) while with Lactococcus lactis subsp. hordniae (M3C) exhibiting the highest gluten degradation and proteolytic activity (53.65 +/- 0.88 tyrosine mu g/mL). Phytase activity test showed that the LAB and yeast isolates (n = 20) exhibited activity ranging from 394.2 to 1011.1 U/mL. p-coumaric acid was degraded between 2.5% and 100% by 23 isolates except one yeast isolate (Rhodotorula alborubescens). Three Lactiplantibacillus plantarum strains (R6B, R7B, R9A), two Weissella confusa strains (R10A, R10B), Lactococcus lactis subsp. hordniae (R4B) and Pedioccus acidilactici (R4A) almost completely degraded both caffeic acid and p-coumaric acid. The acid production levels ranging from 0.7% to 2.5% (mean = 1.39%) of the LAB isolates were observed. Overall, this study provided a valuable insight for production of grain based fermented foods with higher mineral, phenolic and protein bioaccessibility and lower antinutritional properties by using proper LAB and yeast starter cultures.