Production of Proteolytic Enzymes by a Keratin-Degrading Aspergillus niger

Table 3

Main effects and interaction analysis for protease production by A. niger growing on feather meal.

Factors	Effect protease	Standard error	t value	P value
Medium	11.02078	0.355983	30.9588	0.000074*
Feather meal (L)	4.19157	0.504191	8.3135	0.003647*
Feather meal (Q)	−4.54622	0.565214	−8.0434	0.004013*
pH (L)	−1.39211	0.504191	−2.7611	0.070089*
pH (Q)	−9.68345	0.565214	−17.1324	0.000433*
Feather meal × pH	1.25000	0.711972	1.7557	0.177405

𝑅²=0.90.
*Significant factors, 𝑃<0.1.