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Mechanistic studies of a lipase unveil a dramatic effect of pH on the selectivity toward the hydrolysis of PET oligomers
Summary
Researchers studied how pH dramatically affects the selectivity and efficiency of a lipase enzyme when breaking down PET plastic oligomers, revealing mechanistic insights relevant to improving enzymatic plastic recycling processes. The findings highlight pH as a key variable in engineering more effective biocatalysts for plastic degradation.
Abstract Plastic recycling is doubtless a realistic solution for the disposal of plastics and biocatalysis is a key enabling technology for that aim. However, despite advances done in the development of new plastic degrading enzymes, the molecular mechanisms that govern their catalytic performance are poorly understood hampering the engineering of efficient enzyme technology. In this work, we study the hydrolysis of PET oligomers catalysed by the highly promiscuous lipase B from Candida antarctica (CALB) through QM/MM molecular dynamics simulations supported by experimental Michaelis-Menten kinetics. The computational studies reveal the unknown role of the pH on the CALB regioselectivity toward the hydrolysis of bis-(hydroxyethyl) terephthalate (BHET). We exploited this insight to perform pH-controlled biotransformation that selectively hydrolyses BHET to either its corresponding diacid or monoesters using both soluble and immobilized CALB. The discoveries presented here have been exploited for the valorisation of BHET resulting from the organocatalytic depolymerization of PET.