Sequential Biocatalytic Decomposition Of Bhet As Valuable Intermediator Of Pet Recycling Strategy

Sequential biocatalytic process based on lipase catalysis has been developed for the decomposition of bis(2-hydroxyethyl)terephthalate (BHET) as model molecule for polyterephthalic ester (PET) recycling. The sequen-tial process comprised lipase enzyme: (i) hydrolysis of BHET and (ii) esterification of the resulted products (mono (2-hydroxyethyl)terephthalic acid, MHET and terephthalic acid, TPA) using dimethyl carbonate (DMC). Screening of lipases for the BHET hydrolysis revealed Aspergillus niger lipase as a valuable biocatalyst. Further, the sequential biocatalytic process had been evaluated for different concentrations of lipase and DMC. 2% (v/v) DMC afforded an advanced biocatalytic conversion of BHET providing maximum 53 % TPA and 44 % mono-methyl terephthalic acid (MTP1) in the products mixture. Aromatic alcohols as o-cresol, thymol or carvacrol proved also the ability to degrade BHET to TPA and corresponding TPA esters based on sequential biocatalysis.