Table 1 Experimental independent variables at two levels used for the production of cholesterol oxidase by Streptomyces cavourensis strain NEAE-42 using Plackett–Burman design

A

Temperature (°C)

30

37

B

Incubation time (days)

5

7

C

Inoculum size (%, v/v)

2

4

D

Agitation speed (rpm)

150

200

E

pH

7

8.5

F

Glucose (g/L)

10

15

G

Starch (g/L)

7

10

H

Cholesterol (g/L)

1

2

J

Yeast extract (g/L)

4

6

K

Peptone (g/L)

3

5

L

Ammonium sulphate (g/L)

6

8

M

K₂HPO₄ (g/L)

0.5

1

N

NaCl (g/L)

0.5

1

O

MgSO₄ (g/L)

0.2

0.5

P

FeSO₄ (g/L)

0.0

0.02