Table 2 The coded and actual values for the tested variables

X1

pH

2

7

X2

Incubation time

7

16

X3

Peptone

0.5

10

X4

Glucose

2

10

X5

Calcium Chloride

0.1

0.4

X6

Cysteine

4

8

X7

Malt extract

4

10

X8

Fructose

4

10

X9

Sucrose

4

10

X10

Salicylic acid

2

4

X11

Sodium chloride

0.1

0.4

X12

Yeast extract

2

8

X13

Potassium dihydrogene-phosphate

0.1

0.4

X14

Sodium citrate

1

4

X15

Sodium acetate

1

4

X16

Ferric chloride

0.1

0.4

X17

Glycine

1

4

X18

Starch

2

15

X19

Copper sulphate

0.1

0.4