Table 2.

Design matrix and experimental results of Plackett–Burman design

Run no.	Components											Alpha-amylase production (U/gds)
	X1	X2	X3	X4	X5	X6	X7	X8	D1	D2	D3
1	1	1	−1	1	1	1	−1	−1	1	1	−1	9.334
2	−1	1	1	−1	1	1	1	−1	−1	−1	1	0.502
3	1	−1	1	1	−1	1	1	1	−1	−1	−1	3.702
4	−1	1	−1	1	1	−1	1	1	−1	−1	−1	12.746
5	−1	−1	1	−1	1	1	−1	1	1	1	−1	16.474
6	−1	−1	−1	1	−1	1	1	−1	1	1	1	9.308
7	1	−1	−1	−1	1	−1	1	1	1	1	1	21.73
8	1	1	−1	−1	−1	1	−1	1	−1	−1	1	10.26
9	1	1	1	−1	−1	−1	1	−1	1	1	−1	5.50
10	−1	1	1	1	−1	−1	−1	1	1	1	1	19.17
11	1	−1	1	1	1	−1	−1	−1	−1	−1	1	27.63
12	−1	−1	−1	−1	−1	−1	−1	−1	−1	−1	−1	39.05

D1–D3 represent dummy variables