Table 2.

Experimental design and results of Box–Behnken optimization experiment.

Trials	X1 (molasses)		X2 (yeast extract)		X3 (incubation temp.)		EPS (g/L)
	Coded level	Real level (%)	Coded level	Real level (g/L)	Coded level	Real level (°C)	Observed	Predicted
1	0.00	8	1.00	6	−1.00	30	6.92 ± 0.21	7.05
2	1.00	12	−1.00	2	0.00	35	4.55 ± 0.07	4.53
3	0.00	8	1.00	6	1.00	40	7.78 ± 0.51	7.48
4	1.00	12	0.00	4	−1.00	30	6.90 ± 0.09	6.62
5	−1.00	4	0.00	4	1.00	40	5.31 ± 0.02	4.99
6	1.00	12	0.00	4	1.00	40	5.44 ± 0.11	5.59
7	1.00	12	1.00	6	0.00	35	7.16 ± 0.19	7.29
8	0.00	8	−1.00	2	−1.00	30	5.36 ± 0.44	5.65
9	−1.00	4	0.00	4	−1.00	30	4.78 ± 0.66	4.62
10	−1.00	4	−1.00	2	0.00	35	3.97 ± 0.08	3.83
11	0.00	8	−1.00	2	1.00	40	4.69 ± 0.02	4.55
12	0.00	8	0.00	4	0.00	35	5.88 ± 0.11	5.64
13	−1.00	4	1.00	6	0.00	35	5.39 ± 0.09	5.40
14	−1.00	4	0.00	4	1.00	40	4.41 ± 0.58	4.99
15	0.00	8	0.00	4	0.00	35	5.41 ± 0.06	5.64

X₁, molasses (%); X₂, yeast extract (g/L) and X₃, incubation temperature (h).