Mechanistic studies of a lipase unveil a dramatic effect of pH on the selectivity toward the hydrolysis of PET oligomers

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.

A minireview on the bioremediative potential of microbial enzymes as solution to emerging microplastic pollution

“…Hydrolysis produced volatile fatty acids and glycerols that eventually assimilated by the microorganisms to yield lipid acyl chains for cell membrane maintenance (Poddar et al, 2020). Bacterial lipases are also recognized for breaking down plastic polymers like polyurethane (Gautam et al, 2007) and PET oligomers (Swiderek et al, 2022). Various bacterial species were reported to secrete novel lipases, including those from thermophilic and psychrophilic strains (Mobarak-Qamsari et al, 2011;Rabbani et al, 2013;Maiangwa et al, 2014).…”