Unlike traditional recycling strategies, biodegradation is a sustainable solution for disposing of poly(ethylene terephthalate) (PET) waste. PETase, a newly identified enzyme from Ideonella sakaiensis, has high efficiency and specificity towards PET and is, thus, a prominent candidate for PET degradation. On the basis of biochemical analysis, we propose that a wide substrate-binding pocket is critical for its excellent ability to hydrolyze crystallized PET. Structure-guided site-directed mutagenesis revealed an improvement in PETase catalytic efficiency, providing valuable insight into how the molecular engineering of PETase can optimize its application in biocatalysis.

A new method for the selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) has been developed employing a magnetically separable [γ-Fe 2 O 3 @HAP-Pd(0)] catalyst. The catalyst was prepared by the exchange of Pd 2+ with Ca 2+ in γ-Fe 2 O 3 @HAP, followed by reduction of the Pd 2+ to Pd(0) nanoparticles, and well characterized by TEM, XRD and XPS. The catalyst showed high activity in the oxidation of HMF to FDCA in water, with 97% HMF conversion and a 92.9% yield of FDCA under optimal reaction conditions. The method developed has demonstrated some advantages, including its sole requirement of a stoichiometric base, and high catalytic performance under atmospheric oxygen, even in air. More importantly, the γ-Fe 2 O 3 @HAP-Pd(0) catalyst was readily separated from the reaction solution using an external magnetic field and was successfully reused during five consecutive reaction runs while retaining its catalytic effectiveness. This study provides a green and sustainable method for the production of valuable chemicals from renewable resources.

In this study, a magnetically-recoverable catalyst (Fe 3 O 4 @SiO 2 -HPW) was prepared by the application of phosphotungstic acid (HPW) supported on silica-coated Fe 3 O 4 nanoparticles. The prepared samples were characterized by XRD, TEM, FT-IR, and N 2 -adsorption-desorption isotherms. The content of W in Fe 3 O 4 @SiO 2 -HPW was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and its surface acidity was determined by a potentiometric titration with n-butylamine. Fe 3 O 4 @SiO 2 -HPW showed an excellent catalytic activity for the synthesis of EMF from HMF and fructose. Under optimal reaction conditions, EMF was obtained in a high yield of 83.6% by the etherification of 5-hydroxymethylfurfural. EMF could also be synthesized directly from fructose in a yield of 54.8% via a one-pot reaction strategy. After reaction, the catalyst Fe 3 O 4 @SiO 2 -HPW could be easily separated from the reaction mixture with an external magnetic field, and it could be reused at least five times without any loss of its catalytic activity.Scheme 1 Synthesis of EMF from fructose in ethanol.