Variables
Coded levels
–1.682
–1
0
1
1.682
Glucose concentration (g/l), (
X
1
)
0.46
0.6
0.8
1.0
1.14
(NH
4
)
2
SO
4
(g/l), (
X
2
)
0.659
1.0
1.5
2.0
2.341
Metal ion concentration (Mn
2+
) (g/l),(
X
3
)
0.0032
0.01
0.02
0.03
0.0368
Table 1:
Experimental range and levels of the independent variables
