Table 2.

Experimental design and results of the central composite design

Run	pH value	Mannose conc. (g/L)	Meat extract conc. (g/L)	Incubation time (day)	α-Galactosidase activity (U/mL)
					Actual	Predicted	Residual
1	5.5	15	7.5	5	22.528	20.166	2.352
2	4.5	12.5	5	6	17.339	17.749	− 0.410
3	5.5	10	7.5	5	16.708	16.199	0.509
4	4.5	7.5	5	6	10.559	11.684	− 1.124
5	5.5	10	7.5	7	22.959	21.118	1.842
6	4.5	7.5	10	4	11.692	12.034	− 0.342
7	6.5	7.5	5	4	7.023	8.342	− 1.319
8	5.5	5	7.5	5	9.046	10.686	− 1.640
9	4.5	12.5	10	6	25.199	25.436	− 0.237
10	5.5	10	12.5	5	19.059	17.469	1.591
11	6.5	12.5	10	4	12.557	12.988	− 0.431
12	6.5	7.5	5	6	12.367	10.581	1.786
13	5.5	10	7.5	5	15.981	16.199	− 0.218
14	5.5	10	7.5	3	8.925	10.055	− 1.130
15	6.5	7.5	10	4	10.828	9.574	1.254
16	5.5	10	7.5	5	16.327	16.199	0.128
17	5.5	10	7.5	5	16.146	16.199	− 0.053
18	6.5	7.5	10	6	15.765	16.815	− 1.050
19	6.5	12.5	5	4	8.579	7.922	0.658
20	3.5	10	7.5	5	16.439	16.696	− 0.257
21	6.5	12.5	10	6	23.219	25.552	− 2.333
22	4.5	12.5	10	4	15.669	16.612	− 0.942
23	4.5	7.5	10	6	15.722	15.536	0.186
24	4.5	12.5	5	4	13.422	13.928	− 0.506
25	7.5	10	7.5	5	12.938	11.969	0.968
26	5.5	10	7.5	5	16.984	16.199	0.785
27	6.5	12.5	5	6	14.269	15.483	− 1.214
28	5.5	10	2.5	5	7.672	8.551	− 0.879
29	5.5	10	7.5	5	15.047	16.199	− 1.151
30	4.5	7.5	5	4	16.362	13.185	3.177