Table I
Central composite design (CCD) matrix of three independent variables for AgNPs biosynthesis in codes with experimental results.
| Runs | Factor A: Substrate concentration (mM) | Factor B: NaCl concentration (%) | Factor C: Wet weight of biomass (g) | Response: Size of AgNPs (nm) |
|---|---|---|---|---|
| 1 | 1 | 10 | 7 | 33.65 |
| 2 | 3 | 20 | 7 | 127.20 |
| 3 | 2 | 15 | 8.5 | 68.23 |
| 4 | 1 | 20 | 10 | 33.65 |
| 5 | 3 | 1 | 10 | 76.22 |
| 6 | 1 | 20 | 7 | 33.65 |
| 7 | 2 | 15 | 8.5 | 68.20 |
| 8 | 2 | 15 | 8.5 | 68.30 |
| 9 | 2 | 23.41 | 8.5 | 89.37 |
| 10 | 1 | 10 | 10 | 33.65 |
| 11 | 3 | 20 | 10 | 70.48 |
| 12 | 3.68 | 15 | 8.5 | 156.2 |
| 13 | 2 | 15 | 11.02 | 33.65 |
| 14 | 2 | 15 | 8.5 | 33.55 |
| 15 | 2 | 15 | 8.5 | 33.65 |
| 16 | 0.32 | 15 | 8.5 | 126.30 |
| 17 | 2 | 15 | 5.98 | 33.23 |
| 18 | 2 | 6.59 | 8.5 | 33.45 |
| 19 | 3 | 10 | 7 | 127.10 |
| 20 | 2 | 15 | 8.5 | 90.06 |
Fig. 1.
Characterization of AgNPs obtained WO.
A. UV-Vis spectrophotometer analysis representing a peak of AgNPs at 452 nm and showing brown coloured nanoparticles. B. Zeta sizer (DLS) analysis representing peak at 356nm nm. C. Triangular shaped AgNPs revealed by AFM. D. Fourier transform infrared (FT-IR) analysis of AgNPs.
Fig. 2.
Characterization of AgNPs obtained OS.
A. UV-Vis spectrophotometer analysis representing peak of AgNPs at 420 nm and showing medium brown coloured nanoparticles. B. Zeta sizer (DLS) analysis representing peak at 33.23 nm. C. Zeta potential analysis by DLS. D. Spherical shaped AgNPs revealed by AFM. E. Fourier transform infrared (FT-IR) analysis of AgNPs indicating presence of functional groups.
Fig. 3.
A. Colour change observed during the optimization experiments (20 runs). B. Estimation of nitrate reductase activity (nmol/h/ml) and reduction in the size of AgNPs during different RSM experiments.
Table II
Analysis of Variance (ANOVA) of the Fitted Quadratic Model and regression analysis for optimization of AgNPs biosynthesis.
| Source | Sum of Squares | Df | Mean Square | F-Value | p-value | Prob > F |
|---|---|---|---|---|---|---|
| Model | 23241.50 | 9 | 2582.39 | 3.91 | 0.0224 | Significant Significant |
| A – Substrate concentration | 7343.55 | 1 | 7343.55 | 11.11 | 0.0076 | |
| B – NaCl concentration | 572.28 | 1 | 572.28 | 0.87 | 0.3740 | |
| C – Wet weight of biomass | 836.67 | 1 | 836.67 | 1.27 | 0.2868 | |
| AB | 3.98 | 1 | 3.98 | 0.006017 | 0.9397 | |
| AC | 1447.22 | 1 | 1447.22 | 2.19 | 0.1697 | |
| BC | 4.26 | 1 | 4.26 | 0.006451 | 0.9376 | |
| A2 | 9658.74 | 1 | 9658.74 | 14.62 | 0.0034 | Significant |
| B2 | 78.85 | 1 | 78.85 | 0.12 | 0.7369 | |
| C2 | 2154.83 | 1 | 2154.83 | 3.26 | 0.1011 | |
| Residual | 6608.52 | 10 | 660.85 | |||
| Lack of Fit | 4113.14 | 5 | 822.63 | 1.65 | 0.2984 | Not significant |
| Pure Error | 2495.38 | 5 | 499.08 | |||
| Core Total | 29850.02 | 19 | ||||
| Std. dev | C.V | R-Squared | Adj R-Squared | Pred R-Squared | Adeq Precision | |
| 25.71 | 37.53 | 0.7786 | 0.5794 | 0.1664 | 8.801 |
Fig. 4.
3D surface plots analysis. A. Effect of substrate concentration and metal salt concentration. B. Effect of metal salt concentration and substrate concentration. C. Effect of substrate concentration and wet weight of biomass.