Table 5 Effect of metal ions on the activity of the pure keratinase produced by P. citrinum AUMC 14742 (Mean value ± SD with different letters is significantly different (p < 0.05; n = 3).

Control

35,437 ± 1684^bc

100 ± 4.75

NaCl

31,135 ± 1084^e

87.86 ± 3.06^e

KCl

33,360 ± 1449^cde

94.14 ± 4.09^cde

CaCl₂

33,658 ± 1552^cde

94.98 ± 1.56^cde

MgSO₄

32,173 ± 914^de

90.79 ± 2.58^de

FeSO₄

28,318 ± 1828^f

79.91 ± 5.16^f

CuSO₄

25,206 ± 1272^g

71.13 ± 3.59^g

ZnSO₄

36,621 ± 1272^b

103.34 ± 3.59^b

MnSO₄

70,577 ± 1467^a

199.16 ± 4.14^a

CoCl₂

35,880 ± 1754^bc

101.25 ± 2.13^bc

NiCl₂

34,845 ± 1637^bcd

98.33 ± 4.62^bcd