Table 1: Range and levels of experimental variables.

Factors Level of factors
Low (−)Medium (0)High (+)

Sucrose (A/(w/v))4.01016
Yeast extract (B/(w/v))1.02.54.0
NaNO3 (C/(w/v))1.02.03.0
Zn+2 (D/(v/v))1.01.52.0
Triton X-100 (E/(v/v))0.51.01.5