Table 2.

Factors and levels of CCD

Factors	Level
	-1.682	-1	0	+ 1	+ 1.682
A: medium volume (ml)	43	50	60	70	77
B: initial pH	4.3	5.0	6.0	7.0	7.7
F: fermentation temperature (°C)	21.6	25	30	35	38.4