Table 4 Regression analysis and analysis of variance (ANOVA) for the experimental results of the Plackett-Burman design first-order model response total carotenoid production. The coded factors were X₁ = sucrose, X₂ = yeast extract, X₃ = MgSO₄·7H₂O, X₄ = pH, X₅ = incubation time, X₆ = inoculum volume, X₇ = KCl, X₈ = CaCl₂·6H₂O, and X₉ = NaCl. DF means degree of freedom

Model

10

0.33500

1.77045

0.177045

1169.90

0

X₁ (Sucrose)

1

0.0123018

-0.03050

0.01116

0.011163

73.76

0.001

X₂ (Yeast extract)

1

-0.12750

0.19508

0.195075

1289.04

0***

X₃ (MgSO₄·7H₂O)

1

-0.01100

0.00145

0.001452

9.59

0.039

X₄ (pH)

1

0.20333

0.49613

0.496133

3278.41

0***

X₅ (Incubation time)

1

0.04033

0.01952

0.019521

129.00

0***

X₆ (Inoculum volume)

1

0.09783

0.11486

0.114856

758.96

0***

X₇ (KCl)

1

-0.02100

0.00529

0.005292

34.97

0.005

X₈ (CaCl₂·6H₂O)

1

0.02283

0.00626

0.006256

41.34

0.004

X₉ (NaCl)

1

0.05933

0.04225

0.042245

279.15

0***