Heterologous expression and characterization of Aquabacterium parvum lipase, a close relative of Ideonella sakaiensis PETase in Escherichia coli

Polyethylene terephthalate (PET) is a globally mismanaged plastic waste. Microbial degradation of plastics is a green and sustainable technology and very few studies report biocatalysts with plastic degradation potential. The present study aims to investigate the PETase from the evolution of IsPETase. Through NCBI database scanning, Aquabacterium parvum lipase (ApLip) was identified as an evolutionary intermediate between conventional lipases and IsPETase based on 16 S rRNA, amino acid sequences and protein structural similarity by simulation. The codon adaptation index (CAI) was used for ApLip to obtain ApLip-Ec and its protein expression was enhanced in Escherichia coli Lemo21(DE3) with a high catalytic efficiency of 11341 mM⁻¹ min⁻¹ based on p-nitrophenyl butyrate (pNPB) as a substrate. In vitro testing for PET degradation using 5.5 µM ApLip-Ec released 5.9 µM BHET after 48 h. Moreover, the synergism effect of ApLip-Ec and MHETase was explored. Successful PET degradation not only existed in Ideonella sakaiensis, but also evolved from structurally similar cutinases and lipases in nature.