Table 2.

Design matrix of centered central composite design (CCD) for succinic acid production

Run	Glucose	Yeast extract	MgCO3	Succinic acid (g/L)
				Observed	Predicted
1	−1	−1	−1	7.884	6.543
2	+1	−1	−1	10.403	9.609
3	−1	+1	−1	11.692	10.267
4	+1	+1	−1	15.127	15.441
5	−1	−1	+1	3.260	3.138
6	+1	−1	+1	6.223	7.840
7	−1	+1	+1	12.601	13.589
8	+1	+1	+1	18.863	20.399
9	−1.68	0	0	6.782	8.021
10	+1.68	0	0	17.804	16.326
11	0	−1.68	0	0.104	0.586
12	0	+1.68	0	14.998	14.278
13	0	0	−1.68	11.226	13.257
14	0	0	+1.68	16.831	14.562
15	0	0	0	14.447	16.421
16	0	0	0	15.435	16.421
17	0	0	0	15.070	16.421
18	0	0	0	17.425	16.421
19	0	0	0	18.541	16.421
20	0	0	0	17.518	16.421