Synthesis of natural starch from Elaeis guineensis trunk biomass applying bisulphite steeping method: Optimization by RSM

Figures & data

Figure 1. Bonding arrangement of OPTS (Nadhari et al. 2013)

Figure 2. A brief display of the extraction of OPTS

Table 1. Actual values with coded values in parenthesis for the experimental parameters

Experimental Parameters	Actual Value (Coded value)
A. Strength of bisulfite solution	0.2% (−1)	0.6% (0)	1% (+1)
B. Steeping time (hr)	4 (−1)	6 (0)	8 (+1)
C. Mixing ratio with bisulfite solution	1:1 (−1)	1:1.5 (0)	1:2 (+1)
D. Mixing ratio with UPW	1:0.4 (−1)	1:0.5 (0)	1:0.6 (+1)

Table 2. Central composite design outcome for experimental parameters and response (actual and predicted)

	Experimental Design for Process Parameters				Response (%Yield)
Run	A	B	C	D	Actual	Predicted
1	1	6	1	0.6	11	11.34
2	1	4	1.5	0.5	12	11.13
3	0.6	4	1.5	0.4	12.65	12.92
4	1	2	2	0.6	9.5	9.32
5	0.6	6	1.5	0.5	12.8	13.02
6	0.6	4	1.5	0.5	13	12.92
7	1	6	1	0.4	10.5	10.68
8	0.2	6	2	0.6	7.35	6.69
9	0.6	4	1.5	0.5	13	12.92
10	0.6	4	2	0.5	12.8	12.56
11	0.2	6	2	0.4	7.2	7.35
12	0.6	4	1.5	0.5	13	12.92
13	0.6	4	1	0.5	11.8	12.08
14	0.2	2	2	0.4	7.45	7.35
15	0.6	4	1.5	0.5	13	12.92
16	0.2	2	2	0.6	6.15	6.69
17	1	2	2	0.4	8	8.67
18	1	6	2	0.4	11	11.15
19	0.6	4	1.5	0.5	13	12.92
20	0.6	4	1.5	0.5	13	12.92
21	0.2	6	1	0.6	6.65	6.22
22	1	6	2	0.6	12.15	11.81
23	1	2	1	0.6	8.5	8.85
24	0.6	4	1.5	0.6	12.8	12.92
25	1	2	1	0.4	8.5	8.19
26	0.2	2	1	0.4	7.5	6.88
27	0.2	6	1	0.4	6.5	6.88
28	0.2	4	1.5	0.5	7	7.91
29	0.2	2	1	0.6	6.4	6.22
30	0.6	2	1.5	0.5	11.95	11.77

Table 3. ANOVA outcome for modified quadratic model of response surface

Source	Sum of Squares	DF	Mean Square	F-value	p-value
Regression model	193.4	8	24.17	114.91	<0.0001
Residual	4.42	21	0.21
Lack of Fit	4.42	16	0.28

Standard deviation = 0.46; R² = 0.98; adjusted R² = 0.967; predicted R² = 0.94; adequate precision = 27.053; coefficient of variation = 4.49; PRESS = 11.73.

Figure 3. DesignExpert originated plot (a) actual versus predicted; (b) normal probability plot of the residuals

Figure 4. 3D response surface plot, (a) model graph from ANOVA; (b), (c), (d) numerical optimization based on interrelation of parameters

Figure 5. Numerical optimization for four parameters and one response with desirability function

Table 4. Outcomes of verification study at optimum condition

Strength of Bisulfite Solution	Steeping Time (h)	Ratio with Bisulfite Solution	Mixing Ratio with UPW	Model Response	Average Verification Value	%Error	Standard Deviation
0.74	5.6	1.6	0.6	13.54	13.87	2.43	0.165

Figure 6. (a) SEM micrograph of native starch at 4000 magnifications; (b) SEM micrograph of native starch at magnification of 6000s; (c) EDX analysis report for OPTS

Figure 7. (a) XRD analytical shape of OPTS; (b) FTIR spectrum for extracted starch (OPTS)

Table 5. Solubility index (SI) and swelling power (SP) of extracted starch

Temperature (°C)	Swelling Power (SP) (g/g)	Solubility Index (SI) (%)
50	2.52	17.17
60	2.78	19.05
70	6.9	7.46
80	6.53	5.23
90	5.19	2.89

Table 6. A typical costing outline for OPTS synthesis (based on 500 gm OPT processing)

Items	Required Quantity	Price (RM)
OPT collection (depends on the distance of the source)	500 gm	2
Sodium bisulfite	2.8 L	1.1
Ultrapure water	300 mL	0.9
Fiberglass filter 1.6 µm	1p	1.1
Acetone	100 mL	0.9
Total variable cost for 500 gm OPT or about 70 gm OPTS synthesis		6
Total variable cost for 1000 gm or 1 kg OPTS production		85
Nylon screen (1 m*3 m)	1 for 1000 gm starch production	12
Total tentative costing for 1 kg OPTS production		97

Nadhari, W. N. A. W., R. Hashim, O. Sulaiman, M. Sato, T. Sugimoto, and M. E. Selamat. May 2013. Utilization of OPT waste for manufacturing of binderless particleboard: Optimization study. BioResources 8 (2):1675–96. doi:https://doi.org/10.15376/biores.8.2.1675-1696.

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