Table 2.

Analysis of variance (ANOVA) for the fitted quadratic polynomial model of l-DOPA production

Source	Sum of Squares	df	Mean Square	F value	P value Prob > F
Model	4.067057	14	0.290504	19.55822	<0.0001*
X1-pH	0.070994	1	0.070994	4.779684	0.0463*
X3-Yeast extract	0.392047	1	0.392047	26.39459	0.0002*
X7-L-tyrosin	0.45202	1	0.45202	30.4323	<0.0001*
X8-CuSO4	0.262552	1	0.262552	17.67635	0.0009*
X1 X3	0.110889	1	0.110889	7.465614	0.0162*
X1 X7	0.178929	1	0.178929	12.04641	0.0037*
X1 X8	0.05267	1	0.05267	3.54603	0.0806
X3 X7	0.020306	1	0.020306	1.36712	0.2618
X3 X8	0.032041	1	0.032041	2.157164	0.1640
X7 X8	0.069696	1	0.069696	4.692291	0.0480*
X21	1.897243	1	1.897243	127.7321	<0.0001*
X23	0.667645	1	0.667645	44.9493	<0.0001*
X27	0.408899	1	0.408899	27.52919	0.0001*
X28	0.514278	1	0.514278	34.6238	<0.0001*
Residual	0.207946	14	0.014853
Lack of fit	0.186523	10	0.018652	3.482636	0.1203
Pure error	0.021423	4	5.3558
Cor total	4.275003	28

P < 0.05, * Significant P value