Optimization of the Medium Components for the Produc- tion of Phytase. Different concentrations of urea were analyzed (0; 0.15 and 0.30% w/v) to determine the best con- centration that promotes the production of phytase. Higher concentrations of urea result in decreased phytase activity when S. cerevisiae is cultured in sodium phytate substrate. At a concentration of 0.15% urea, the activity of phytase was 0.41 U/mL, while at 0.30% urea we observed an activity of 0.33U/mL. Urea is the preferred nitrogen sources for the production of phytase by Aspergillus ficuum [5] and Pichia anomala [13].