TABLE 7.

Analysis of variance (ANOVA) for the response value quadratic model.

Source	Sum of squares	df	Mean square	F value	P value	Significance
Model	2430.64	14	173.62	47.53	<0.0001	***
A	261.87	1	261.87	71.70	<0.0001	***
B	41.55	1	41.55	11.38	0.0046	**
C	122.30	1	122.30	33.48	<0.0001	***
D	28.62	1	28.62	7.83	0.0142	*
AB	37.75	1	37.75	10.33	0.0062	**
AC	11.73	1	11.73	3.21	0.0948
AD	0.099	1	0.099	0.027	0.8715
BC	22.05	1	22.05	6.04	0.0277	*
BD	0.21	1	0.21	0.057	0.8149
CD	43.35	1	43.35	11.87	0.0039	**
A 2	477.59	1	477.59	130.76	<0.0001	***
B 2	509.18	1	509.18	139.41	<0.0001	***
C 2	589.45	1	589.45	161.39	<0.0001	***
D 2	711.93	1	711.93	194.92	<0.0001	***
Residual	51.13	14	3.65
Lack of fit	44.55	10	4.46	2.71	0.1748
Pure error	6.58	4	1.65
Cor total	2481.77	28

*Significant at P < 0.05; **Significant at P < 0.01; ***Significant at P < 0.001. R² = 0.9794, Adj R² = 0.9588, Pred R² = 0.8990. A, culture time; B, temperature; C, pH; D, inoculum volume. They are four factors in response surface test, as the independent variables. AB, interaction between culture time and temperature; AC, interaction between culture time and pH; AD, interaction between culture time and inoculum volume; BC, interaction between temperature and pH; BD, interaction between temperature and inoculum volume; CD, interaction between pH and inoculum volume. A², The quadratic term of culture time; B², The quadratic term of temperature; C², The quadratic term of pH; D², The quadratic term of inoculum volume.