Table 2.

Central composite rotatable design (CCRD) matrix of independent variables (for media components and process parameters) with their experimental and predicted response (surface tension)

Run	Variables			Surface tension (mN/m)
	X (C-conc.  %)	Y (N-conc. %)	Z (pH)	Experimental	Predicted
Media components
1	7	0.3	10	54.43	54.94
2	5	0.783	7	29.93	29.43
3	5	0.5	7	30.59	30.84
4	5	0.5	7	31.59	30.84
5	5	0.5	2.76	58.40	57.89
6	5	0.5	7	30.64	30.84
7	3	0.7	10	27.61	28.12
8	5	0.5	11.24	62.12	61.61
9	5	0.5	7	29.67	30.84
10	7	0.7	4	32.78	33.29
11	7.83	0.5	7	38.02	37.51
12	2.17	0.5	7	26.32	25.81
13	5	0.5	7	30.67	30.84
14	3	0.3	4	67.76	68.26
15	5	0.217	7	34.54	34.03

Run	Variables			Surface tension (mN/m)
	A (temperature, °C)	B (incubation time, h)	C (inoculum size, %)	Experimental	Predicted
Process parameters
1	37.5	72	4	26.734	25.78
2	37.5	72	6.83	29.813	30.29
3	30	96	6	24.917	24.44
4	37.5	72	4	26.172	25.78
5	37.5	72	4	25.814	25.78
6	45	48	6	64.13	63.65
7	37.5	38.06	4	30.692	31.17
8	45	96	2	50.106	49.63
9	30	48	2	23.755	23.28
10	48.1	72	4	54.961	55.44
11	37.5	105.9	4	32.655	33.13
12	37.5	72	4	25.128	25.78
13	26.9	72	4	25.757	26.23
14	37.5	72	1.17	35.826	36.30
15	37.5	72	4	25.984	25.78

The bold values indicate the optimized parameters corresponding to minimal surface tension