Table 3.

Fit summary for of CCD for AuNPs biosynthesis using Streptomyces flavolimosus cell-free supernatant as affected by temperature (°C), incubation period (days), HAuCl₄ concentration (µg/mL) and initial pH level.

Source	Sum of squares	Df	Mean square	F-value	P-value
Lack of fit tests
Linear	254,400	20	12,718.18	55.46	0.0001*
2FI	162,800	14	11,625.48	50.69	0.0002*
Quadratic	9360.18	10	936.02	4.08	0.067

Source	Std. dev.	R2	Adjusted R2	Predicted R2	PRESS
Model summary statistics
Linear	101.10	0.7206	0.6758	0.5828	381,500
2FI	92.88	0.8207	0.7264	0.7071	267,800
Quadratic	26.47	0.9885	0.9778	0.9392	55,565.78

df degree of freedom, two factors interaction: 2FI.

*Significant values.