Experimental design approach in recombinant protein expression: determining medium composition and induction conditions for expression of pneumolysin from Streptococcus pneumoniae in Escherichia coliand preliminary purification process

Table 4 Variables and levels assayed

	Inferior level	Central level	Superior level
	(-1)	(0)	(+1)
Induction absorbance (Abs_ind)	0.8	1.4	2.0
IPTG (mM)	0.1	0.55	1.0
Expression temperature (°C)	25	31	37
Yeast extract (g/L)	5	14.3	23.6
Tryptone (g/L)	0	5	10
Glucose (g/L)	1	5.5	10
Glycerol (%v/v)	0	0.2	0.4
Kanamycin (μg/mL)	10	30	50

ISSN: 1472-6750