Phytase is a subgroup of phosphatases which catalyzes the hydrolysis of myo-inositol hexakisphosphate (phytic acid) to inorganic monophosphate and lower myoinositol phosphates. A diet rich in cereal fibers, legumes and soy protein results in an increased uptake of phytate. Phytic acid has been shown to have a strong anti-nutritive effect in animal as pigs, poultry, fish and human. Undigested phytate negatively affects the absorption of Ca2+, Fe2+, Zn2+ and reduction of phosphate content. It also reduces the digestability of proteins and inhibits digestive enzymes. In addition, some isomers of myo-inositol phosphates have been implicated in blood glucose response, lowering of cholesterol, renal stone formation, in the treatment of Alzheimer’s disease, multiple sclerosis and certain types of cancer. Phytases could also be used soil amendment and in plant growth promotion. A phytase in which there is a commercial interest should fulfill a series of quality criteria. As the stomach is the main functional site of supplemental phytase, an enzyme should be effective in releasing phytate phosphate in the digestive tract, stable to resist inactivation by acidic pH and heat from feed processing. In this study, samples picked up from a hot spring and inoculated in phytase screening medium. Samples were incubated for 2 days at 40ºC in an orbital shaker (180 rpm). Then all samples were inoculated on PSM agar. A clearing zone around the bacteria colony on PSM plates represents extracellular phytase activity. Bacteria with the highest clear halo have been purified on the specific media. Phytase from thermophilic bacteria have been partially purified using ammonium sulphate fractionation followed by dialysis. Phytase activity and phosphate releasing was determined by end point method. Stability and activity of phytase was assayed in temperature range of 30-90 ºC and a pH range of 2-11. Results showed that the enzyme was active and stable in high temperature, and it,s maximum temperature activity was observed in 60 °C. In addition, this enzyme was stable between pH 2-11, but the optimal pH activity was found to be pH 8.0. These results indicated that this phytase can be used in wide range of biotechnological applications.
کلید واژگان :purification; thermostable; phytase; activity; biotechnology
ارزش ریالی : 300000 ریال
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