关键词: 聚对苯二甲酸乙二醇酯, 超声, 生物降解, 角质酶, 二级结构

Abstract: Polyethylene terephthalate （PET） is a typical linear thermoplastic resin material，which is widely used in manufacture of fiber，film and beverage bottle.While PET brings many conveniences to human life，its property of difficult degradation has caused serious white pollution and threatened the global environment.In this research，the cutinase LCC was successfully expressed with Escherichia coli BL21 （DE3），and the optimized condition in E.coli BL21（DE3） expression is：inducer isopropyl-β-D-thiogalactopyranoside（IPTG）=0.2 mmol/L，induction temperature =16 ℃，and induction time =20 h.After protein purification process via Ni-affinity chromatography，the enzyme activity of LCC is 320 U/mg.Subsequently，the purified LCC was used to degrade PET with ultrasound，and their reaction conditions were optimized.Under the conditions of reaction temperature= 65℃，pH =8.0，ultrasonic power = 25 W，ultrasonic time=5 h，Km is the smallest and V_max is the largest，the degradation efficiency of LCC with ultrasound is 1.21 times higher than that of untreated，and the product terephthalic acid concentration of （TPA） increases from 0.72 g/L to 0.87 g/L.According to the scanning electron microscopy （SEM），the degradation of PET catalyzed by LCC can be accelerated by ultrasound.The circular dichroism （CD） spectroscopy and fourier transform infrared （FT-IR） spectroscopy show that the α-helix and β-sheets of LCC secondary structure are possibly transformed into random coils with ultrasound.Thus，the degradation of PET catalyzed by LCC can be improved by ultrasonic process.This study provides some theoretical basis for the ultrasonic accelerated degradation reaction and opens up a new idea for the biodegradation of PET.

Key words: polyethylene terephthalate, ultrasound, biodegradation, cutinase, secondary structure