Evaluation of invertase activity in Yeasts isolated from saline soil

Biodiversity of yeasts in extreme habitats and applications in food industry attract many of researchers. The aim of this study was evaluation of invertase activity in isolated yeasts from saline soil. In this study, kinetic activity of invertase from 27 halophilic and halotolerant yeast strains isolated from salin soil of Qom and Arak were evaluated. After collection of soil samples, the yeasts were cultured on YPD Agar containing 5% salt. Out of 27 yeast strains, 2 halophilic and 6 halotolerant strains with invertase activity were assessed for selection of best strain. Assessment of invertase activity according to the Glucose Oxidase assay showed that the enzyme productivity of G5 strain is more powerful than other isolates. The optimum enzyme activity was obtained at 65C and pH 4.5. The highest enzymatic activity was observed in the medium containing 1.7mM sodium chloride. Na+, Mg2+ and Ca2+ ions (all chlorides and 5mM concentration) have stimulation effect on enzyme's activity. The Km of enzyme for sucrose was 20 mM. Thermal stability of enzyme in 65C was one hour and decrease of activity is not observed. According to the results of this study, G5 strain has able to produce invertase in different concentrations of different salts.