Functionalization of amylopectin as a strategy to improve polyethylene terephthalate hydrolase-cross-linked enzyme aggregate (IsPETase-CLEA) in plastic degradation

Polyethylene terephthalate hydrolase-cross-linked enzyme aggregate cross-linked with amylopectin (IsPETase/Amy) was developed and successfully degraded polyethylene terephthalate (PET). However, the low enzyme efficiency of IsPETase/Amy may hamper its industrial application. Hence, the goal of this study is to improve the enzyme efficiency of IsPETase-CLEAs by using novel dialdehyde amylopectin (DAA) from maize as cross-linker. DAA with aldehyde content of 64.3 % was synthesized and used to cross-link IsPETase as IsPETase/DAA. Under best immobilization condition, the activity recovery achieved was 74.3 %. Furthermore, IsPETase/DAA achieved 3.0-, 2.63-, 1.72- and 2.4-fold better thermal stability compared to IsPETase/Amy at 35 °C, 40 °C, 45 °C and 50 °C respectively. Moreover, better pH stability (pH 5-10) was achieved by IsPETase/DAA, and the reusability was enhanced to 7 cycles. Besides, enzyme efficiency of IsPETase/DAA successfully improved 7-fold better than IsPETase/Amy. It was revealed that IsPETase/DAA exhibited better PET degradation that the MHET yield was 66.2 % and 28 % higher than free IsPETase and IsPETase/Amy respectively. Therefore, this study developed a new promising green biocatalyst in PET degradation to be applied in industry.