Optimization of Acid Protease Production by Aspergillus niger I1 on Shrimp Peptone Using Statistical Experimental Design

Table 1

Levels of the factors tested for the production of proteases by A. niger I1 using Plackett-Burman design.

Variables	Unit	Lower level (−1)	Higher level (+1)
Temperature	°C	25	30
Hulled grain of wheat	g/L	5	15
Shrimp peptone	g/L	2	5
KH2PO4	g/L	1	2
MgSO4	g/L	0.5	1
NaCl	g/L	0.3	0.6
pH		5	8
ZnCl2	g/L	0.1	0.2
Na2HPO4	g/L	0.8	1.6
CaCl2	g/L	0.4	0.8
Inoculum’s size	Sp/mL	5×10^6	10^7

Sp: spores.