Table 2.

Analysis of the two-level Plackett–Burman design

Variable	Regression coefficient	t value	Sig.	Ranks
Glucose	0.472	1.09	0.3887	7
Peptone	− 3.348	− 7.76	0.0162	1
KCl	1.92	4.45	0.0470	2
NaH2PO4	− 0.363	− 0.84	0.4886	8
NaCl	− 1.162	− 2.69	0.1148	5
pH	1.202	2.78	0.1085	4
Inoculum size	1.695	3.93	0.0592	3
Temperature	− 0.748	− 1.73	0.2252	6
Fermentation time	− 0.3	− 0.69	0.5590	9