Phytase catalyzes the breakdown of complex organic forms of phosphorus into simpler forms by sequential hydrolysis of phosphate-ester bonds to release inorganic phosphate. Supplementation of feed with bacterial phytase can therefore improve the bioavailability of phosphorus and trace elements. In the present study, the production of phytase by a strain of Cobetia marina isolated from the lye of the Burgas salt pans and the optimization of culture conditions to enhance phytase production are reported. The effects of physical conditions and nutrients on phytase production were investigated. Physical parameters studied included fermentation time, inoculum size, agitation, pH and temperature. Maximum growth, as well as enzyme production (15.3 U mg-1) were recorded after 72 h incubation period. To increase the level of enzyme production, different culture conditions were applied and the optimum temperature and pH for phytase production were found to be 35oC and pH 7.5, respectively. Nutrient factors studied included carbon source, nitrogen source, substrate type and concentration, NaCl concentration and metal ions (salts). Our studies showed that the optimum phytase production was achieved using a mineral medium supplemented with: 1.5% maltose, 0.5% NaNO3, 0.7% sodium phytate and 7% NaCl. Among the metal ions tested K+, Mn2+ and Fe2+ were found to have no effect on enzyme production. However, the removal of Ca2+ and Mg2+ from the production medium, lead to a decrease in strain growth and phytase production. Metal ions like Co2+, Zn2+, Ni2+, Hg2+, Ag2+ and the various detergents tested, caused a significant inhibition on phytase production. As a result of the optimization approaches applied the production level of phytase was enhanced 2.7-fold and (40.5 U mg-1) compared to the initial enzyme yield.
Boyadzhieva et al. (Wed,) studied this question.