Improved production of Bacillus subtilis cholesterol oxidase by optimization of process parameters using response surface methodology

Journal of Genetic Engineering and Biotechnology

Table 4 Statistical analysis of the Box–Behnken experimental results

Effect	Cholesterol degradation (%)				Cholesterol oxidase activity (U/OD₆₀₀)
Effect	Parameter coefficient	Standard error	Computed t-value	p-value	Parameter coefficient	Standard error	Computed t-value	p-value
Intercept	59.66667	1.062704	56.14607	0.000000	61.8389	1.769442	34.94825	0.000000
X₁	− 9.87500	1.301542	− 7.58716	0.000064*	− 11.9391	2.147324	− 5.55998	0.000535*
X₁²	− 0.29167	0.957909	− 0.30448	0.768530	− 1.2354	1.580387	− 0.78172	0.456889
X₂	− 3.25000	1.301542	− 2.49704	0.037113*	− 2.6584	2.147324	− 1.23803	0.250803
X₂²	− 0.41667	0.957909	− 0.43498	0.675076	− 0.3972	1.620404	− 0.24511	0.812545
X₃	− 7.12500	1.301542	− 5.47428	0.000591*	− 8.3226	2.147324	− 3.87581	0.004703*
X₃²	− 0.29167	0.957909	− 0.30448	0.768530	− 1.9300	1.580387	− 1.22120	0.256776

^*Significant (p-value ≤ 0.05)
For cholesterol degradation (%): X₁, X₂, and X₃ are the cholesterol concentration (g/l), the inoculum size (%), and the concentration of magnesium sulphate (g/l), respectively
For the activity cholesterol oxidase (U/OD₆₀₀): X₁, X₂, and X₃ are pH, volume of the medium (ml/flask) and cholesterol concentration (g/l), respectively