Influence of culture conditions on production of phytase by Zygosaccharomyces bailii var. bailii

摘要

Microbial phytases are phosphohydrolytic enzymes which are gaining attention for their commercial exploitation in feed and food industry. In the present study, ten yeasts were isolated from different soil samples and screened for their phytase producing capability. Among these isolates, the most promising yeast strain was Zygosaccharomyces bailii var. bailii which produced highest phytase yield (6.36 U ml(-1)) in malt yeast extract glucose peptone (MYGP) medium. In order to improve phytase production by Zygosaccharomyces bailii, different physio-chemical parameters were optimized. The optimal conditions for phytase production was found to be: incubation time-42 hr, temperature-30 degrees C, medium pH-6.0 and substrate (calcium phytate) concentration-0.1%. Glucose at 0.5% concentration supported higher phytase production (13.75 U ml(-1)) than other carbon sources tested. Metal ions (Ca++, K+, Mg++) and additives; ethylene diamine tetraacetate (EDTA), sodium dodecyl sulphate (SDS) and toluene did not affect enzyme production. However, Zn++, Ni++, Ba++, Pb++ and detergents like Triton X-100 and Tweens strongly inhibited (>90%) phytase production. An overall 2.21-fold enhancement in phytase activity (6.36-->14.03 U ml(-1)) was attained after optimization studies.