Table 2 Analysis of variance 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 of variance | Coefficient estimate | Sum of squares | Degrees of freedom | Mean square | F-value | P-value | |
|---|---|---|---|---|---|---|---|
Model | Intercept | 575.71 | 903,800 | 14 | 64,560.43 | 92.17 | < 0.0001* |
Linear effect | X1 | 20 | 9600.34 | 1 | 9600.34 | 13.71 | 0.0021* |
X2 | − 39.19 | 36,859.26 | 1 | 36,859.26 | 52.62 | < 0.0001* | |
X3 | 152.55 | 558,500 | 1 | 558,500 | 797.39 | < 0.0001* | |
X4 | 47.37 | 53,847.92 | 1 | 53,847.92 | 76.88 | < 0.0001* | |
Interaction effect | X1 X2 | 17.98 | 5173.71 | 1 | 5173.71 | 7.39 | 0.0159* |
X1 X3 | 43.36 | 30,080.84 | 1 | 30,080.84 | 42.94 | < 0.0001* | |
X1 X4 | − 19.82 | 6287.27 | 1 | 6287.27 | 8.98 | 0.009* | |
X2 X3 | − 32.95 | 17,370.86 | 1 | 17,370.86 | 24.8 | 0.0002* | |
X2 X4 | 37.35 | 22,323.96 | 1 | 22,323.96 | 31.87 | < 0.0001* | |
X3 X4 | 25.46 | 10,370.3 | 1 | 10,370.3 | 14.81 | 0.0016* | |
Quadratic effect | X12 | − 1.8 | 88.83 | 1 | 88.83 | 0.1268 | 0.7267 |
X22 | − 10.37 | 2950.84 | 1 | 2950.84 | 4.21 | 0.058 | |
X32 | − 8.85 | 2150 | 1 | 2150 | 3.07 | 0.1002 | |
X42 | − 74.24 | 151,200 | 1 | 151,200 | 215.84 | < 0.0001* | |
Error effect | Lack of fit | 9360.18 | 10 | 936.02 | 4.08 | 0.067 | |
Pure error | 1146.64 | 5 | 229.33 | ||||
R2 | 0.9885 | ||||||
Adj R2 | 0.9778 | ||||||
Pred R2 | 0.9392 | ||||||
Adeq Precision | 35.3418 | ||||||
