The most important alkaline proteases from the commercial standpoint are produced by bacteria of the genus Bacillus and used mainly in the formulation of detergents. The aim of the present study was to evaluate the production, partial purification, and characteristics of alkaline protease obtained by Bacillus firmus var. arosia NCIB 10557 in fed-batch fermentation with constant feeding profile and carbon source restriction. Firstly, it was carried out on batch fermentation and after 6.5 h of fermentation, glucose became limiting, and then the fed-batch was started with a flow rate of 0.0802 mL/min. Maximum activity (998.1 U/mL) was reached after 10.5 h of fed-batch, with a subsequent 60.91 % drop in activity after two hours. The purification steps resulted in a 1.65-fold increase in the value of the specific activity. The protease showed optimum activity at 37°C and pH 9 and residual activity above 80 % at pH 11 and 12. Residual activity was greater than 70 % at temperatures ranging from 30 to 70 °C and 90 % of this activity was maintained for 30 minutes at 70 °C until the occurrence of complete inactivation. Enzyme activity was estimated using SDS. The organic solvents Triton X-100, Tween-20, EDTA and β-mercaptoethanol and the ions Zn2+, Fe2+, Cu2+ and Ni2+ partially inhibited the activity of the protease. Ca2+, Mn2+ and Mg2+ had no stimulating action on the enzyme.