Table 2.

Levels of the variables and statistical analysis in PB design for 2-PE production

Code	Variable	Low level (-1)	High level (+ 1)	Effect (EXi)	F values	P values	Rank	Significance
X1	Yeast extract concentration (g/L)	2	10	− 0.0408	0.10	0.757	8
X2	L-Phe concentration (g/L)	5	15	1.2643	99.48	0.000	2	**
X3	pH	1	3	1.4225	125.93	0.000	1	**
X4	Temperature (oC)	22	30	0.4097	10.45	0.014	5	*
X5	Shaking speed (rpm)	210	270	− 0.0411	0.10	0.755	7
X6	Loading volume (mL/250 mL)	12.5	37.5	− 1.1368	80.43	0.000	3	**
X7	Tween-60 concentration (g/L)	16	48	0.2909	5.27	0.055	6
X8	Time (h)	48	72	0.5553	19.19	0.003	4	**

*Significant at 5% level (P < 0.05); **Significant at 1% level (P < 0.01)