Skip to main content
Bioresources and Bioprocessing

Table 1 Factors and value levels used in the central composite design

From: Recombinant d-galactose dehydrogenase partitioning in aqueous two-phase systems: effect of pH and concentration of PEG and ammonium sulfate

Factors

Factor code

Inferior levela(−1)

Center pointa(0)

Superior levela(+1)

PEG (%, w/w)

X 1

13

14

15

Salt (%, w/w)

X 2

11

12

13

pH

X 3

7

7.5

8

  1. aLevel 0 represents the central level of each factor in the intended ranges to evaluate the background variability in the process; levels −1 and +1 are the factorial points, i.e., the high and low levels of each factor in the intended range.
Back to article page