Broad-spectrum biodegradation of aliphatic and aliphatic-aromatic polyesters by Papiliotrema laurentii isolated from locust frass.

Abstract

Biodegradable aliphatic and aliphatic-aromatic polyesters, such as poly(butylene adipate-co-terephthalate) (PBAT), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), and polyhydroxyalkanoates (PHA), are increasingly used as sustainable alternatives to petrochemical plastics. However, their depolymerization outside industrial composting facilities is often incomplete. This study characterized Papiliotrema laurentii strain 62UF-13, isolated from migratory locust frass, for broad-spectrum polyester hydrolysis. Emulsion assays demonstrated hydrolytic activity across all five polymers, with PCL and PBS showing the highest clearance rates. Solid-film assays revealed substantial gravimetric mass loss of PCL, PLA, and PHA cast films, whereas a commercial PBAT-PLA mulch film in minimal medium, underwent progressive fragmentation/disintegration, as assessed by the remaining film area. Incubation with the PBAT-PLA film was accompanied by the release of adipic acid (49.60 mg/L, week 1) and terephthalic acid (maximum 21.62 mg/L, week 4), followed by a decrease to 0.26 mg/L by week 8, coinciding with the emergence of putative 3,4-dihydroxymandelic acid and a putative acetylated derivative. Scanning electron microscopy (SEM) revealed pronounced pitting and erosion, while Fourier-transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) indicated ester-bond scission and changes in crystallinity/melting behavior. Whole-genome sequencing identified eight candidate polyesterases, including cutinases and esterases, with ≥ 60% amino acid identity to known hydrolases active on PCL, PBS, PHA, and PLA. This study is the first report of P. laurentii degrading a broad range of aliphatic and aliphatic-aromatic polyesters, including partial biotransformation of terephthalate moieties from PBAT. Integration of phenotypic assays and genomic evidence positions P. laurentii 62UF-13 as a viable biocatalyst for decentralized management of biodegradable plastic waste under mild environmental conditions.