Table 5 Estimated effects, regression coefficients and corresponding P-values of second order polynomial model for CaCO₃ weight and CA activity optimized by CCD

Constant

0.912857

0.04778

19.106

0

88.95

4.884

18.214

0

Linear effects

Glucose

0.104167

0.0258

4.037

0.001

10.6792

2.637

4.049

0.001

Ca acetate

0.185

0.0258

7.17

0

18.9958

2.637

7.202

0

NaNO₂

0.063333

0.0258

2.454

0.026

5.8942

2.637

2.235

0.04

Inoculum size

0.176667

0.0258

6.847

0

17.9375

2.637

6.801

0

Quadratic effects

(Glucose)²

− 0.123214

0.02364

− 5.212

0

− 11.578

2.416

− 4.792

0

(Ca-acetate)²

− 0.135714

0.02364

− 5.741

0

− 12.866

2.416

− 5.325

0

(NaNO₂)²

− 0.089464

0.02364

− 3.785

0.002

− 7.2135

2.416

-2.985

0.009

(Inc.size)²

− 0.105714

0.02364

− 4.472

0

− 10.0035

2.416

4.14

0.001

Interaction effects

glucose*Ca acetate

0.065

0.0316

2.057

0.056

6.6688

3.23

2.064

0.056

Glucose* NaNO₂

− 0.07875

0.0316

− 2.492

0.024

− 8.0812

3.23

− 2.502

0.024

Glucose * Inc. Size

0.0525

0.0316

1.661

0.116

5.3688

3.23

1.662

0.116

Ca-acetate* NaNO₂

0.09

0.0316

2.848

0.012

9.2313

3.23

2.858

0.011

Ca-acetate*Inc. Size

0.00125

0.0316

0.04

0.969

0.1062

3.23

0.033

0.974

NaNO₂* Inc. Size

0.035

0.0316

1.108

0.284

3.5813

3.23

1.109

0.284

S = 0.1264

R-Sq = 93.1%

R-Sq(adj) = 87%

R-Sq = 92.7%

R-Sq(adj) = 86.2%