Assessing the bread-leavening ability of wild yeasts isolated from selected fruits collected from local markets.

Abstract

Yeasts play a crucial role in converting sugars in flour into carbon dioxide (CO2) and ethanol, enabling dough leavening. This study focused on identifying efficient wild yeast strains isolated from various fruits for leavening under controlled laboratory conditions. Of the 88 wild yeast isolates obtained, three (AAUGr5, AAUOr7, and AAUPi3) were selected based on their ability to produce CO2 efficiently, using D-glucose (3 g/L) as a substrate and their non-hydrogen sulfide (H2S) production character. These isolates were tentatively identified as members of the Saccharomyces genus through cultural, morphological, and biochemical analyses and optimal physicochemical profiling. Optimal growth conditions in Yeast Extract Peptone Dextrose (YPD) medium were a pH of 5 and a temperature of 30 °C. Maximum growth was observed with 2% (w/v) D-glucose and 0.5% (w/v) NaCl concentrations, achieving peak biomass after 96 hrs of incubation. Notably, isolate AAUGr5 displayed superior leavening performance compared to commercial yeast with 9.09% and 8.92% at 30 °C and room temperature, respectively. Furthermore, a co-culture of these H2S-free wild yeast strains demonstrated enhanced leavening activity, underscoring their potential for baking applications to produce high-quality bread.