Enzymatic degradation of poly(butylene succinate) by cutinase cloned from Fusarium solani

摘要

A gene encoding cutinase from Fusarium solani was cloned and overexpressed in Pichia pastoris. The recombinant cutinase with a molecular weight of 24 kDa was then purified to homogeneity. The enzyme presents degradation capacity for poly(butylene succinate) (PBS) and exhibits the optimum pH and temperature of 8.0 and 50 ℃, respectively. Enzyme activity is enhanced by K~+ and Na~+ and inhibited by Zn~(2+), Fe~(2+), Mn~(2+), and Co~(2+). The inhibitions of different chemicals on recombinant enzyme activity were examined. EDTA and β-mercaptoethanol exert significant inhibitory effect. The degradation of PBS films in the presence of the recombinant enzyme was further studied. Results showed that enzymatic degradation is a rapid process, and the PBS films were degraded completely after approximately 6 h. The characteristics of PBS films after degradation were analyzed. With the extension of degradation time, the surfaces of PBS films became rougher and holes appeared with a gradually increasing trend. Differential scanning calorimetry and scanning electron microscopy analyses revealed that both amorphous and crystalline regions of PBS were degraded by the recombinant enzyme. Wide-angle X-ray diffractometer also indicated the crystallinity of PBS has a gradual downward trend with the extension of degradation time. Gel permeation chromatography showed the molecular weight of PBS has no obvious change before and after degradation.