Table 2. Analysis of variance (ANOVA) for response surface model.

Source	Sum of Squares	Df	Mean Square	F-Value	p-value (Prob > F)
Model	5537.76	14	395.55	550.96	<0.0001	significant
A-Cysteamine	228.81	1	228.81	318.7	<0.0001
B-Glutaraldehyde	512.21	1	512.21	713.45	<0.0001
C- Functionalized graphene	0.02	1	0.02	0.03	0.8672
D-Enzyme	1346.2	1	1346.2	1875.09	<0.0001
AB	210.25	1	210.25	292.85	<0.0001
AC	108.16	1	108.16	150.65	<0.0001
AD	20.25	1	20.25	28.2	0.0001
BC	16	1	16	22.29	0.0003
BD	26.01	1	26.01	36.23	<0.0001
CD	764.52	1	764.52	1064.89	<0.0001
A2	834.5	1	834.5	1162.36	<0.0001
B2	1791.19	1	1791.19	2494.9	<0.0001
C2	343.77	1	343.77	478.83	<0.0001
D2	218.58	1	218.58	304.46	<0.0001
Residual	10.05	14	0.72
Lack of Fit	8.86	10	0.89	2.97	0.1526	not significant
Pure Error	1.19	4	0.3
Cor Total	5547.81	28

R-Squared = 0.998188; Adj R-Squared = 0.996377; Pred R-Squared = 0.990466.