Table 1
Experimental design for RSM
| SR # | Temperature (°C) | Time (min) | Acid conc. (%) | Substrate conc. (g) | Glucose conc. (mg mL‒1) |
|---|---|---|---|---|---|
| 1 | 30 | 20 | 3 | 1 | 35.201 |
| 2 | 30 | 20 | 3 | 4 | 59.110 |
| 3 | 30 | 60 | 0.5 | 1 | 130.112 |
| 4 | 30 | 60 | 0.5 | 4 | 71.211 |
| 5 | 30 | 20 | 0.5 | 1 | 77.341 |
| 6 | 30 | 20 | 0.5 | 4 | 80.322 |
| 7 | 60 | 40 | 1.75 | 2.5 | 177.109 |
| 8 | 60 | 40 | 1.75 | 2.5 | 181.214 |
| 9 | 30 | 60 | 3 | 1 | 44.221 |
| 10 | 60 | 40 | 4.25 | 2.5 | 11.298 |
| 11 | 60 | 40 | 1.75 | 5.5 | 123.765 |
| 12 | 60 | 40 | 0.25 | 2.5 | 149.246 |
| 13 | 60 | 10 | 1.75 | 2.5 | 69.776 |
| 14 | 60 | 80 | 1.75 | 0.5 | 101.209 |
| 15 | 30 | 60 | 3 | 4 | 14.117 |
| 16 | 60 | 40 | 1.75 | 0.5 | 120.328 |
| 17 | 20 | 40 | 1.75 | 2.5 | 116.821 |
| 18 | 90 | 20 | 0.5 | 1 | 260.671 |
| 19 | 60 | 40 | 1.75 | 2.5 | 178.109 |
| 20 | 90 | 20 | 0.5 | 4 | 329.432 |
| 21 | 90 | 60 | 0.5 | 1 | 363.119 |
| 22 | 100 | 60 | 1.75 | 2.5 | 429.220 |
| 23 | 60 | 40 | 1.75 | 2.5 | 179.402 |
| 24 | 60 | 40 | 1.75 | 2.5 | 177.712 |
| 25 | 90 | 60 | 3 | 1 | 285.996 |
| 26 | 90 | 20 | 3 | 1 | 248.556 |
| 27 | 90 | 20 | 3 | 4 | 306.245 |
| 28 | 60 | 40 | 1.75 | 2.5 | 180.127 |
| 29 | 90 | 60 | 0.5 | 4 | 350.478 |
| 30 | 90 | 60 | 3 | 4 | 229.492 |
Source: Author’s contribution.
Figure 1
Fourier-transform infrared spectroscopy (FTIR) spectrum of P. pinnata seeds.
Source: Author’s contribution.
Table 2
FTIR Spectrum of Pongamia pinnata seeds
| Sr. # | Wave number (cm−1) | Functional group | Bond |
|---|---|---|---|
| 1 | 3273.11 | Alcohol | O–H |
| 2 | 2920.51 | Alkane | C–H |
| 3 | 2850.99 | Alkane | C–H |
| 4 | 1708.89 | Carbonyl | C–O |
| 5 | 1624.30 | Alkenes | C–C |
| 6 | 1405.47 | Phenols | –OH bending vibrations, –C–O–H in-plane bending vibrations,–CH3 out-of-plane bending vibrations, –CH2 – wagging and twisting vibrations |
| 7 | 1227.37 | Amines | N–H, C–O (hemicellulose) |
| 8 | 1020.53 | Halogen | C–F (guaiacyl unit of lignin) and C–O (primary alcohol and cellulose) |
| 9 | 756.02 | Halogen | C–Cl |
Source: Author’s contribution.
Figure 2
Alcohol to oil ratio used in the transesterification of P. pinnata oil (a), and Biodiesel after Washing the Oil & Transesterification Process (b). X-Axis represent the different alcohol to oil ratios used and SD was calculated for n = 3.
Source: Author’s contribution.
Table 3
Coded and uncoded values of the variables for the Box–Behnken design
| Sr. # | Coded values of variables | −α | −1 | 0 | +1 | +α |
|---|---|---|---|---|---|---|
| Variables uncoded values | ||||||
| 1 | Temperature (°C) | 30 | 60 | 80 | 90 | 100 |
| 2 | Acid concentrations (%) | 0.25 | 0.5 | 1.75 | 53 | 4.25 |
| 3 | Time (min) | 20 | 30 | 40 | 60 | 80 |
| 4 | Substrate concentrations (g) | 0.5 | 1 | 2.5 | 4 | 5.5 |
Source: Author’s contribution.
Figure 3
Contour (a) and 3D response surface plot (b) showing the interactive effects of incubation time (min) and substrate concentration (g) on glucose concentration activity during enzymatic hydrolysis of P. pinnata seed biomass. The red dot represents the experimental design point, while the color gradient indicates enzyme activity levels ranging from low (blue, 11.29 U mL−1) to high (red, 429.22 U mL−1). Actual factors were fixed at temperature = 60°C and acid concentration = 1.75%.
Source: Author’s contribution.
Figure 4
Contour (a) and 3D response surface plot (b) showing the interactive effects of temperature (°C) and substrate concentration (g) on glucose concentration during enzymatic hydrolysis of P. pinnata seed biomass. The red dot represents the experimental design point, while the color gradient indicates enzyme activity levels ranging from low (blue, 11.29 U mL−1) to high (red, 429.22 U mL−1). Actual factors were fixed at acid concentration = 2.5% and temperature 40°C.
Source: Author’s contribution.
Figure 5
Contour (a) and 3D response surface plot (b) showing the interactive effects of acid concentration (%) and temperature (°C) on glucose concentration during enzymatic hydrolysis of P. pinnata seed biomass. The red dot represents the experimental design point, while the color gradient indicates enzyme activity levels ranging from low (blue, 11.29 U mL−1) to high (red, 429.22 U mL−1). Actual factors were fixed at D: acid concentration = 2.5% and B: temperature 40°C.
Source: Author’s contribution.
Figure 6
Optimization of substrate concentration on glucose release and ethanol yield during fermentation. (a) Effect of varying substrate concentrations (0.5, 1.0, 1.5, and 2.0%) on glucose release (mg mL−1) over 72 h. (b) Corresponding ethanol yield (%) measured at different time intervals (12–72 h). Ethanol production increased steadily, reaching a maximum of 6.77% after 72 h, indicating efficient conversion of glucose into ethanol at optimal conditions.
Source: Author’s contribution.
Table 4
Seeds for sustainable biodiesel and bioethanol production
| Source | Sum of squares | df | Mean square | F-value | p-value | |
|---|---|---|---|---|---|---|
| Model | 3.545 × 10+5 | 14 | 25319.56 | 78.65 | <0.0001 | Significant |
| A-temperature | 2.655 × 10+5 | 1 | 2.655 × 10+5 | 824.65 | <0.0001 | |
| B-time | 1226.37 | 1 | 1226.37 | 3.81 | 0.0699 | |
| C-acid conc. | 14299.02 | 1 | 14299.02 | 44.41 | <0.0001 | |
| D-subs. conc. | 45.74 | 1 | 45.74 | 0.1421 | 0.7115 | |
| AB | 280.38 | 1 | 280.38 | 0.8709 | 0.3655 | |
| AC | 45.81 | 1 | 45.81 | 0.1423 | 0.7113 | |
| AD | 891.32 | 1 | 891.32 | 2.77 | 0.1169 | |
| BC | 3673.57 | 1 | 3673.57 | 11.41 | 0.0041 | |
| BD | 6855.05 | 1 | 6855.05 | 21.29 | 0.0003 | |
| CD | 1.70 | 1 | 1.70 | 0.0053 | 0.9431 | |
| A² | 42696.64 | 1 | 42696.64 | 132.62 | <0.0001 | |
| B² | 11642.50 | 1 | 11642.50 | 36.16 | <0.0001 | |
| C² | 9683.89 | 1 | 9683.89 | 30.08 | <0.0001 | |
| D² | 2324.56 | 1 | 2324.56 | 7.22 | 0.0169 | |
| Residual | 4829.19 | 15 | 321.95 | |||
| Lack of fit | 4816.85 | 10 | 481.68 | 195.10 | <0.0001 | Significant |
| Pure error | 12.34 | 5 | 2.47 | |||
| Cor total | 3.593 × 10+5 | 29 |
Source: Author’s contribution.
Table 5
Model Summary
| S | R-sq | R-sq (adjusted) | R-sq (predicted) |
|---|---|---|---|
| 17.94 | R 2 = 98.66% | 97.40% | 93.70% |
Source: Author’s contribution.