Table 3.

Box-Behnken design and observed response value (extraction yield, Y), including actual and predicted code, with different combination of the range of pH value (X₁), content of potassium nitrate (X₂) and the inoculum volume(X₃).

Run order	Factor value			DNJ content (%)
	X1	X2 (%)	X3 (mL)	Actual value	Predicted value
1	6.5(−1)	0.8(0)	1.5(−1)	0.301	0.28
2	7.5(1)	0.8(0)	1.5(−1)	0.219	0.24
3	7.0(0)	0.6(−1)	1.5(−1)	0.203	0.22
4	6.5(−1)	0.8(0)	2.5(1)	0.288	0.28
5	7.0(0)	1.0(1)	2.5(1)	0.256	0.24
6	7.0(0)	1.0(1)	1.5(−1)	0.212	0.20
7	7.0(0)	0.6(−1)	2.5(1)	0.195	0.20
8	7.0(0)	0.8(0)	2.0(0)	0.505	0.54
9	6.5(−1)	1.0(1)	2.0(0)	0.214	0.26
10	6.5(−1)	0.6(−1)	2.0(0)	0.208	0.22
11	7.0(0)	0.8(0)	2.0(0)	0.544	0.54
12	7.5(1)	0.8(0)	2.5(1)	0.210	0.24
13	7.5(1)	0.6(−1)	2.0(0)	0. 243	0.22
14	7.5(1)	1.0(1)	2.0(0)	0.189	0.18
15	7.0(0)	0.8(0)	2.0(0)	0.595	0.54

Numbers in parentheses were coded symbols for levels of independent parameters.