Table 1.

Regression coefficients, R², p-value of lack of fit for the Polynomial Response Surface.

Regression coefficient	Specific activity (Y1)	Temperature stability (Y2)	Storage stability (Y3)	Surfactant agent stability (Y4)
b0	15.14	77.01	81.74	79.82
b1	3.50	11.62	24.58	12.96
b2	5.50	13.33	15.20	24.70
b3	0.53	−11.72	11.74	14.31
b12	2.52	4.15	4.38	8.65
b22	1.88	18.11	25.04	24.04
b32	1.92	9.40	13.38	15.57
b1b2	0.51	12.30	4.90	5.49
b1b3	5.36	11.73	13.02	21.04
b2b3	2.50	17.73	27.24	26.95
R2	0.984	0.978	0.889	0.980
p-value	0.001 *	0.001 *	0.004 *	0.002 *
Lack of fit (p-value)	105.77	195.10	102.99	111.87

¹, B/S ratio; ², Temperature; ³ pH of buffer; * Significant (p < 0.05); b_i, b_ii and b_ij: the estimated regression coefficient for the main linear quadratic and interaction effects, respectively.