Table 1 Gradient setting of each factor in single factor optimization experiment

Media single-factor optimization

Orange peel (g/L)

100

200

300

400

500

600

700

800

900

1000

Type of nitrogen source

NH₄Cl

1.5

-

-

-

-

-

-

-

-

(NH₄)₂SO₄

1.5

-

-

-

-

-

-

-

-

(NH₄)₂HPO₄

1.5

-

-

-

-

-

-

-

-

NaNO₃

1.5

-

-

-

-

-

-

-

-

Casein

1.5

-

-

-

-

-

-

-

-

Peptone

1.5

-

-

-

-

-

-

-

-

Yeast extract

1.5

-

-

-

-

-

-

-

-

yeast extract &peptone

1.5

-

-

-

-

-

-

-

-

Fermentation condition single-factor optimization

(NH₄)₂HPO₄ (g/L)

0.5

1

1.5

2

2.5

3

4

-

-

Incubation time (h)

12

24

36

48

60

72

84

96

-

Inoculation size (%) (v/v)

1

2

4

6

8

10

12

-

-

Initial pH

5

6

6.5

7

7.5

8

9

10

-

Salinity (%)

0

2

5

7.5

12.5

15

17.5

20

-

Temperature (^oC)

25

30

35

37

40

45

50

-

-

Agitation rate (rpm)

0

50

150

200

250

-

-

-

-