Table 4 Medium modified using the Design Expert 7.0 optimization tool for DLA production by L. coryniformis subsp. torquens

Factor

Goal

Lower limit

Upper limit

Importance

 Sodium acetate

Minimize

− 2

2

3

 Meat extract

Minimize

− 2

2

5

 Dipotassium phosphate

Minimize

− 2

2

3

 Yeast extract

Minimize

− 2

2

4

 D(−) lactic acid

Maximize

7.06

12.29

5

Factor

Coded values

Real values (g/L)

Desirability

 Sodium acetate

− 2.00

0.05

0.715

 Meat extract

− 1.08

3.23

 Dipotassium phosphate

− 2.00

0.05

 Yeast extract

− 0.43

2.63

Response

Prediction

SE Pred

95% PI low

95% PI high

 d-lactic acid (DLA, g/L)

9.70

0.80

8.04

11.35