No. Variables/levelsa L-ornithine （g/L） X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15 1 + + + + + + + + - - - - - - - 7.75 2 - + + + + + + + + - - - - - - 11.56 3 - - + + + + + + + + - - - - - 8.96 4 - - - + + + + + + + + - - - - 9.38 5 - - - - + + + + + + + + - - - 7.47 6 - - - - - + + + + + + + + - - 11.13 7 - - - - - - + + + + + + + + - 11.42 8 - - - - - - - + + + + + + + + 10.06 9 + - - - - - - - + + + + + + + 7.96 10 + + - - - - - - - + + + + + + 11.31 11 + + + - - - - - - - + + + + + 9.79 12 + + + + - - - - - - - + + + + 8.98 13 + + + + + - - - - - - - + + + 7.43 14 + + + + + + - - - - - - - + + 9.64 15 + + + + + + + - - - - - - - + 8.63 16 - - - - - - - - - - - - - - - 9.87 aX1, Glucose at a high level of 125 and a low level of 100; X2, K2HPO4 at a high level of 0.625 and a low level of 0.500; X3 , (NH4)2SO4 at a high level of 6.25 and a low level of 5.00; X4, MgSO4∙7H2O at a high level of 3.125 and a low level of 2.500; X5, Yeast extract at a high level of 25 and a low level of 20; X6, KH2PO4 at a high level of 1.25 and a low level of 1.00; X7, Na2HPO4 at a high level of 0.625 and a low level of 0.500; X8, FeSO4∙7H2O at a high level of 0.025 and a low level of 0.020; X9, MnSO4∙4H2O at a high level of 0.025 and a low level of 0.020; X10, molasses at a high level of 2.5 and a low level of 2.0; X11, CaCO3 at a high level of 12.5 and a low level of 10.0; X12, KAc at a high level of 6.25 and a low level of 5.00; X13, succinic acid at a high level of 6.25 and a low level of 5.00; X14, Tween80 at a high level of 1.25 and a low level of 1.00; X15, dummy variable.

Table 1: Plackett-Burman experiment design matrix for screening of culture of L-ornithine production