Evidences of the Hydrolysis of Bis(2-hydroxyethyl) Terephthalate Coupled with the Simultaneous Immobilization of CalB onto Terephthalic Acid

Abstract

A novel and low-cost methodology for the preparation of an active enzyme/support biocatalyst through the hydrolysis of bis(2-hydroxyethyl) terephthalate (BHET), with the simultaneous immobilization of Candida antarctica (CalB) lipase, is presented. The lipase catalyzes the hydrolysis of BHET toward terephthalic acid (TPA) and ethylene glycol (EG) at 37 °C (in 24 h) while also remaining tightly immobilized onto TPA. Experimental evidence suggests that EG acts as a surface functionalization agent, enabling the immobilization of CalB. Furthermore, the enzymatic action renders a crystalline TPA with characteristics that are rather different from the commercial one in terms of specific surface area and porous structure. The highest immobilization yield and catalytic activity were achieved with 3.2% CalB/TPA biocatalyst prepared using an aqueous solution containing 2.83 mg.mL−1 of protein and 600 mg of BHET (BHET/Co = 212). This material catalyzes 60% conversion of rac-ibuprofen to ethyl esters at 60 °C in 30 h. Preliminary results strongly suggest that the methodology described above is suitable for application to BHET obtained through the chemical degradation of PET (polyethylene terephthalate) from urban solid waste (USW).