Optimization of permeabilization process of yeast cells for catalase activity using response surface methodology

Figures & data

Table 1. Values of independent variables at different levels of the central composite rotatable design.

	Real value of variables
Coded value (level)	Temperature (°C)	Ethanol concentration (%)	Time (min)
−1.682	6.6	24.8	7
−1	10	35	20
0	15	50	40
1	20	65	60
1.682	23.4	75.2	73

Table 2. Experimental design.

	Temperature x1		Ethanol concentration x2		Time x3		Response A
Run	Coded values	Un-coded values (°C)	Coded values	Un-coded values (%)	Coded values	Un-coded values (min)	Enzyme activity (U/g)
1	−1	10	−1	35	−1	20	141.1
2	−1	10	1	65	−1	20	2642.3
3	−1	10	−1	35	1	60	180.5
4	−1	10	1	65	1	60	2886.9
5	1	20	−1	35	−1	20	436.7
6	1	20	1	65	−1	20	1900.7
7	1	20	−1	35	1	60	1801.1
8	1	20	1	65	1	60	1746.5
9	1.682	23.4	0	50	0	40	100
10	−1.682	6.6	0	50	0	40	189.4
11	0	15	1.682	75.2	0	40	941.4
12	0	15	−1.682	24.8	0	40	120.3
13	0	15	0	50	1.682	73	3904.6
14	0	15	0	50	−1.682	6	1631.2
15	0	15	0	50	0	40	4693
16	0	15	0	50	0	40	4707.7
17	0	15	0	50	0	40	4724.6
18	0	15	0	50	0	40	4366.7
19	0	15	0	50	0	40	4523.9
20	0	15	0	50	0	40	4590.1

Table 3. Estimated regression coefficients.

Term	Coefficient	SE coefficient	T DF = 10	p-value
x0	4583.58	235.77	19.441	0.000
x1	−19.58	156.42	−0.125	0.903*
x2	585.58	156.42	3.744	0.004
x3	389.36	156.42	2.489	0.032
	−1476.39	152.25	−9.697	0.000
	−1323.99	152.25	−8.696	0.000
	−533.27	152.25	−3.503	0.006
x1x2	−474.77	204.38	−2.323	0.043
x1x3	115.76	204.38	0.566	0.584*
x2x3	−164.17	204.38	−0.803	0.440*

Note: R = 0.948; R² = 0.974; R²(adjusted) = 0.910.

SE coefficient: standard error of coefficient; T: test coefficient; DF: degree of freedom.

*Non-significant at 5% level.

Table 4. Analysis of variance (ANOVA) for the quadratic model.

Source	SS	DF	MS	F-value	p-value
Regression	168,083,823	10.00	16,808,382	50.28913	0.0000003
Residual	3,341,684	10.00	334,168

Note: SS: sum of squares; DF: degree of freedom; MS: mean square.

Figure 1. Response surface plots showing the effect of temperature, ethanol concentration and permeabilization time, their combined effects on the enzyme activity (a)–(c); (a) temperature and ethanol concentration, (b) temperature and permeabilization time, (c) ethanol concentration and permeabilization time.

Figure 2. Changed activity of yeast cells during storage.