Table 4.

Central composite design representing uricase production by Aspergillus welwitschiae as affected by incubation time (days) (X₁), inoculum size (mL/50 mL medium) (X₂) and yeast extract (g/L) (X₃) with actual and coded factor levels.

Std	Run	Type	Variables			Uricase activity (U/mL)					Residuals
			X1	X2	X3	Experimental			Predicted
8	1	Factorial	1	1	1	36.28			39.61		−3.33
15	2	Center	0	0	0	60.03			58.08		1.95
5	3	Factorial	−1	−1	1	38.19			38.41		−0.22
14	4	Axial	0	0	1.68	34.56			32.82		1.74
17	5	Center	0	0	0	55.47			58.08		−2.61
12	6	Axial	0	1.68	0	42.33			40.29		2.04
13	7	Axial	0	0	−1.68	40.02			40.82		−0.80
18	8	Center	0	0	0	57.29			58.08		−0.79
20	9	Center	0	0	0	58.2			58.08		0.12
11	10	Axial	0	−1.68	0	35.88			36.98		−1.10
16	11	Center	0	0	0	59.11			58.08		1.03
7	12	Factorial	−1	1	1	36.95			36.67		0.28
9	13	Axial	−1.68	0	0	44.74			46.40		−1.66
10	14	Axial	1.68	0	0	59.01			56.41		2.60
3	15	Factorial	−1	1	−1	41.41			41.89		−0.48
4	16	Factorial	1	1	−1	50.65			51.09		−0.44
1	17	Factorial	−1	−1	−1	39.11			36.44		2.67
19	18	Center	0	0	0	58.21			58.08		0.13
2	19	Factorial	1	−1	−1	44.46			45.41		−0.95
6	20	Factorial	1	−1	1	40.93			41.12		−0.19
Variable					Code	Coded and actual levels
						−1.68	−1	0		1	1.68
Incubation time (days)					X1	3.32	4	5		6	6.68
Inoculum size (mL/50 mL medium)					X2	2.32	3	4		5	5.68
Yeast extract (g/L)					X3	1.16	1.5	2		2.5	2.84