Table 4.

Estimated effects and variance analysis of the tested variables on keratinolytic activity, concentration of soluble protein, feather degradation, and bacterial growth using 2³ fractional factorial design to analyses the variable MgSO₄, CaCl₂, and MnCl₂ in feather media supplemented with yeast extract

Source	Keratinolytic activity (U/ml)				Concentration of protein (mg/ml)				Feather degradation (%)				B. subtilis AMR growth (UFC/ml)
	Effect	Std errror	F Value	p value	Effect	Std error	F Value	p value	Effect	Std error	F Value	p value	Effect	Std error	F Value	p value
Model			26.65	0.0366			4.66	0.1882			674.45	0.0015			600.33	0.0017
Intercept	300.84	3.20			3.44	0.050			71.89	0.11			21.94	0.38
A-MgSO4	5.87	3.20	3.36	0.2082	0.041	0.050	0.66	0.5013	− 0.041	0.11	0.15	0.7343	10.65	0.38	775.67	0.0013
B-CaCl2	− 4.83	3.20	2.28	0.2705	− 0.082	0.050	2.69	0.2427	3.18	0.11	904.69	0.0011	− 11.96	0.38	977.74	0.001
C-MnCl2	32.13	3.20	100.52	0.0098	0.039	0.050	0.61	0.5177	− 5.25	0.11	2458.85	0.0004	− 7.31	0.38	365.06	0.0027
AB	19.54	3.20	37.20	0.0258	0.066	0.050	1.77	0.3151	3.74	0.11	1249.26	0.0008	− 2.7	0.38	49.68	0.0195
AC	15.83	3.20	24.42	0.0386	0.18	0.050	13.09	0.0686	− 0.66	0.11	38.44	0.0250	− 6.28	0.38	269.84	0.0037
BC	13.63	3.20	18.08	0.0511	0.038	0.050	0.58	0.5249	− 0.85	0.11	63.92	0.0153	12.19	0.38	1015.71	0.001
ABC	− 2.67	3.20	0.69	0.4929	0.18	0.050	13.19	0.0681	0.26	0.11	5.86	0.1365	10.47	0.38	748.61	0.0013
Center Point	60.94	6.14	98.65	0.0100	0.29	0.096	9.38	0.0921	2.45	0.20	146.36	0.0068	− 15.91	0.73	472	0.0021
Std. dev	9.06				0.14				0.3				1.08
Mean	317.46				3.52				75.56				17.6
CV %	2.85				4.02				0.41				6.15
R2	0.9894				0.9422				0.9996				0.9995
Adjusted R2	0.9894				0.7398				0.9981				0.9979
Adq prec	17				7.343								83.972

Prob > F values less than 0.05 indicate that the terms are significant

"Adeq Prec" (adequate precision) measures the signal-to-noise ratio. A ratio greater than 4 is desirable