Table 2 The levels of each factor in the plackett–burman experimental design

A

Orange peel concentration (g/L)

600

1000

B

Temperature (^oC)

35

40

C

Sodium chloride (%)

10

15

D

Incubation time (hr.)

72

96

E

Inoculum size (%) (v/v)

2

10

F

Agitation rate (rpm)

120

180

G

MgCl₂.6H₂O (g/L)

1.35

4.05

H

MgSO₄.7H₂O (g/L)

1.7

5.1

J

(NH₄)₂HPO₄ (g/L)

1.0

3.0

K

Methanol (co-substrate) (g/L)

2.0

4.0

L

Initial pH

5

8