Abstract
Urease production by bacteria represents the key elements of several environmental processes including wastewater treatment, fertilizers management, and bio-cement processes. Maximizing urease production from the microbial strains is considered the first step for efficient utilization of the product. Bacillus subtilis OQ119616 was isolated from Sahel Salim soil sample and identified phenotypic and genotypic using 16SrRNA gene sequence. Box–Behnken statistical experimental design with 13- runs were utilized to optimize and evaluate the interaction effects, main effects, and the quadratic effects of four different Ca-salts on the OD (600 nm) and urease specific activity by Bacillus subtilis in liquid media. The maximum specific activity of urease enzyme for calcium chloride was 0.540 (predicted value 0.558) obtained in run (9) using urea 20 g/l (A), calcium chloride 20 g/l (B), and pH 6 (C), while calcium nitrate was 0.441 (predicted value 0.418) obtained in run (4) using urea 30 g/l (A), calcium nitrate 10 g/l (B), and pH 6 (C). For calcium acetate was 0.435 (predicted value 0.430) obtained in run number (12) using urea 10 g/l (A), calcium acetate 1.5 g/l (B), and pH 6 (C), while calcium citrate was 0.653 (predicted value 0.666) obtained in run number (10) using urea 30 g/l (A), calcium citrate 100 M (B), and pH 8 (C). R2 values of urease specific activities were 0.979 (calcium chloride), 0.981 (calcium nitrate), 0.973 (calcium acetate), and 0.981 (calcium citrate) which indicated that the whole variations were explained highly and accurately by the statistical model.