Enhanced ethyl butyrate production using immobilized lipase

Figures & data

Table I. Coded value of the independent variables and experimental ranges.

		Range and levels
Variables	Design variables	−1.68	−1	0	1	1.68
Enzyme concentration (%, w/V)	X1	11.59	15	25	20	28.41
Substrate concentration (M)	X2	0.13	0.18	0.25	0.35	0.37
Mole ratio butyric acid/ethanol (mol/mol)	X3	0.18	0.36	0.63	0.9	1.08

Table II. Experimental matrix and values of observed response.

No	X1, % (w/V)	X2, M	XE, mol/mol	Experimental response, Y, % (Conversion into ester)
1	15.00	0.18	0.36	0.0048
2	25.00	0.18	0.36	0.0137
3	15.00	0.32	0.36	0.0113
4	25.00	0.32	0.36	0.0200
5	15.00	0.18	0.90	0.0092
6	25.00	0.18	0.90	0.0108
7	15.00	0.32	0.90	0.0106
8	25.00	0.32	0.90	0.0118
9	11.59	0.25	0.63	0.0034
10	28.41	0.25	0.63	0.0231
11	20.00	0.13	0.63	0.0065
12	20.00	0.37	0.63	0.0201
13	20.00	0.25	0.18	0.0106
14	20.00	0.25	1.08	0.0015
15	20.00	0.25	0.63	0.0168
16	20.00	0.25	0.63	0.0174
17	20.00	0.25	0.63	0.0210
18	20.00	0.25	0.63	0.0205
19	20.00	0.25	0.63	0.0203
20	20.00	0.25	0.63	0.0204

Table III. Analysis of variance (anova) for the quadratic model.

Source	Coefficient estimate	Sum of squares	DF	F value	Prob > F
Intercept	0.020		1
x1	3.92 * 10 ^− 3	2.101 * 10^−4	1	30.27	0.0003
x2	2.78 * 10 ^− 3	1.056 * 10^−4	1	15.21	0.0030
x3	−1.66 * 10 ^− 3	3.743 * 10^−5	1	5.39	0.0426
x1^2	−2.18 * 10 ^− 3	6.840 * 10^−5	1	9.85	0.0105
x2^2	−2.15 * 10 ^− 3	6.641 * 10^−5	1	9.57	0.0114
x3^2	−4.71 * 10 ^− 3	3.195 * 10^−4	1	46.02	< 0.0001
x1x2	−7.13 * 10 ^− 5	4.061 * 10^−8	1	5.851 * 10^−3	0.9405
x1x3	−1.85 * 10 ^− 3	2.742 * 10^−5	1	3.95	0.0749
x2x3	−1.30 * 10 ^− 3	1.355 * 10^−5	1	1.95	0.1927
Model		7.903 * 10^−4	9	12.65	0.0002
Residual		6.941 * 10^−5	10
Lack of fit		6.675 * 10^−5	5	25.01	0.0015
Pure error		2.668 * 10^−6	5
Cor Total		8.598 * 10^−4	19

Figure 1. Contour plot of conversion into ester: the effect of enzyme and substrate concentration and their mutual interaction on ethyl butyrate production. other variable is held at zero level.

Figure 2. Contour plot of conversion into ester: the effect of mole ratio, enzyme concentration and their mutual interaction on ethyl butyrate production. other variable is held at zero level.

Figure 3. Contour plot of conversion into ester: the effect of mole ratio, substrate concentration and their mutual interaction on ethyl butyrate production. other variable is held at zero level.

Figure 4. Effect of Na₂HPO₄ Salt on ethyl butyrate production.