During the ultrasound-assisted enzymatic extraction (UAEE), the crude TFP was processed simultaneously by ultrasonic wave and enzymes.
On the basis of preliminary single factor experimental design, a Box-Behnken design (BBD) with four variables ([X.sub.1], pH; [X.sub.2], enzyme amount; [X.sub.3], extraction temperature; [X.sub.4], liquidto-solid ratio) at three levels was used to further determine the optimal UAEE condition of crude TFP extraction [5, 9].
To investigate the effect of different pH conditions on the yield of crude TFP, the extraction process of UAEE was performed for 30 min at different pH conditions with the enzyme amount 6000 u/g, extraction temperature 50[degrees]C, and liquid-to-solid ratio 40ml/g (Figure 1(a)).
The procedure of UAEE was then performed for 30 min at different temperatures (35, 40, 45, 50, 55, 60, and 65[degrees]C) with the following condition: pH 4.5, enzyme amount 6000 u/g, and liquid-to-solid ratio 40 ml/g.
Screening of the appropriate ratio of liquid-to-solid is very important during UAEE , which can facilitate the combination of the plant cells to the active site of the cellulase and the dissolubility of crude TFP in solvent.