Response surface methodological approach for optimizing production of geranyl propionate catalysed by carbon nanotubes nanobioconjugates

Figures & data

Table 1. Independent test variables and their levels used for central composite design.

		Range and levels
Variable	Unit	−2	−1	0	1	2
Time	h	2	4	6	8	10
Temperature	°C	40	45	50	55	60
Solvent	log P	0.8	1.48	2.5	4	6
Molar ratio	MR	1	2	3	4	5

Table 2. Composition of the various runs of the central composite design, actual and predicted responses.

	Variable
Run no.	Time (h)	Temperature (°C)	Solvent (log P)	Molar ratio	Actual yield (%)	Predicted yield (%)
1	8.00	45.00	1.48	2.00	36.4	34.70
2	4.00	45.00	1.48	4.00	36.2	29.81
3	6.00	50.00	2.50	3.00	40.4	40.19
4	8.00	55.00	4.00	4.00	37.9	38.07
5	4.00	55.00	4.00	4.00	35.9	35.87
6	8.00	55.00	1.48	4.00	36.4	36.22
7	4.00	55.00	4.00	2.00	36.2	36.22
8	6.00	50.00	2.50	3.00	40.4	40.19
9	4.00	45.00	1.48	2.00	28.1	28.11
10	8.00	55.00	1.48	2.00	35.9	36.11
11	6.00	50.00	2.50	3.00	40.4	40.19
12	4.00	55.00	1.48	4.00	31.8	31.87
13	8.00	45.00	4.00	2.00	35.5	35.57
14	8.00	45.00	4.00	4.00	33.1	33.01
15	4.00	55.00	1.48	2.00	29.7	29.86
16	4.00	45.00	4.00	2.00	30.9	31.12
17	8.00	45.00	1.48	4.00	34.4	34.51
18	4.00	45.00	4.00	4.00	30.4	30.46
19	8.00	55.00	4.00	2.00	39.8	40.32
20	6.00	50.00	2.50	3.00	40.4	40.19
21	6.00	50.00	2.50	5.00	37.9	38.25
22	10.00	50.00	2.50	3.00	38.2	37.85
23	6.00	50.00	0.80	3.00	40.1	40.48
24	6.00	50.00	6.00	3.00	40.5	40.25
25	6.00	60.00	2.50	3.00	45.2	44.83
26	6.00	50.00	2.50	1.00	38.9	38.35
27	6.00	40.00	2.50	3.00	38.5	38.66
28	6.00	50.00	2.50	3.00	44.1	44.95
29	6.00	50.00	2.50	3.00	45.3	44.95
30	2.00	50.00	2.50	3.00	28.5	28.64

Table 3. Analysis of variance and model coefficients.

Source	Sum of squares	Degree of freedom	Mean square	F-value	P-value
Model	514.20	14	514.20	183.84	<0.0001
A – time	115.39	1	115.39	577.57	<0.0001
B – temperature	69.21	1	69.21	346.39	<0.0001
C – solvent	30.37	1	30.37	152.02	<0.0001
D – molar ratio	0.45	1	0.45	2.26	0.1551
AB	0.12	1	0.12	0.61	0.4467
AC	4.67	1	4.67	23.35	0.0003
AD	3.61	1	3.61	18.07	0.0008
BC	11.36	1	11.36	56.85	<0.0001
BD	0.090	1	0.090	0.45	0.5130
CD	5.66	1	5.66	28.32	0.0001
A^2	234.02	1	234.02	1171.35	<0.0001
B^2	17.53	1	17.53	87.75	<0.0001
C^2	50.49	1	50.49	252.72	<0.0001
D^2	75.63	1	75.63	378.57	<0.0001
Residual	2.80	14	0.20
Lack of fit	2.08	10	0.21	1.15	0.4836
Pure error	0.72	4	0.18
Cor total	657.45	29

Figure 1. Comparison between the predicted and actual values for the conversion of geranyl propionate catalysed by the CRL-MWCNTs nanobioconjugates.

Figure 2. Response surface plot showing the effect of time (A) and solvent (C) and their interaction in the enzymatic production of geranyl propionate.

Figure 3. Response surface plot showing the effect of reaction time (A) and molar ratio (D) and their interaction in the enzymatic production of geranyl propionate.

Figure 4. Response surface plot showing the effect of solvent (C) and temperature (B) and their mutual interaction in the enzymatic production of geranyl propionate.

Figure 5. Response surface plot showing the effect of solvent (C) and molar ratio (D) and their interaction in the enzymatic production of geranyl propionate.

Table 4. The attained optimum conditions for geranyl propionate enzymatic production under the preferred conditions for the shortest reaction time.

No	Time (h)	Temperature (°C)	Solvent (log P)	Molar ratio (alcohol:acid)	Predicted yield (%)	Actual yield (%)	Deviation (%)
1*	4.00	50.00	2.50	3.00:1	48.9	47.4	1.5
2*	4.01	53.34	3.29	3.49:1	45.3	44.6	0.7

Note: (*) denotes the optimum conditions for the highest yield for minimum reaction time proposed by the model.