Table 2.

Plackett–Burman (PB) design for screening of culture conditions affecting the alginate lyase production of strain A3

Run	X1	X2	X3	X4	X5	X6	X7	X8	X9	X10	X11	Enzyme activity (U/ml)
1	1.2	180	0.4	36	25	7	2	3	1	− 1	− 1	1.10
2	1.2	120	0.6	24	25	8	1	3	1	1	− 1	1.51
3	1.2	120	0.4	36	20	8	2	2	1	1	1	4.37
4	1.8	180	0.6	24	20	7	2	2	1	1	− 1	4.11
5	1.8	120	0.4	24	25	7	2	3	− 1	1	1	1.39
6	1.8	180	0.4	36	25	8	1	2	− 1	1	− 1	2.02
7	1.8	120	0.6	36	25	7	1	2	1	− 1	1	1.26
8	1.2	180	0.6	24	25	8	2	2	− 1	− 1	1	2.24
9	1.2	180	0.6	36	20	7	1	3	− 1	1	1	3.59
10	1.8	180	0.4	24	20	8	1	3	1	− 1	1	4.42
11	1.2	120	0.4	24	20	7	1	2	− 1	− 1	− 1	2.46
12	1.8	120	0.6	36	20	8	2	3	− 1	− 1	− 1	6.67

X₁, NH₄NO₃ (w/v, %); X₂, rotation speed (rpm); X₃, L. japonica root powder (w/v, %); X₄, fermentation time (h); X₅, fermentation temperature (°C); X₆, pH; X₇, inoculum size (%); X₈, sea salt concentration (w/v, %); X₉, X₁₀ and X₁₁, dummy variables