Halopseudomonas sp. MFKK-1: A marine-derived bacterium capable of degrading poly(butylene succinate-co-adipate), poly(ε-caprolactone), and poly(butylene adipate-co-terephthalate) in marine ecosystems

Abstract

Aliphatic and aliphatic-aromatic polyesters are potentially biodegradable polymers that have garnered attention as promising solutions to plastic waste menace, particularly in marine environments. Among these, poly(butylene succinate-co-adipate) (PBSA), which has polyethylene-like properties, is used as biodegradable packaging and mulch film. However, the slow degradation of PBSA in marine environments presents a challenge. We isolated a polyester-degrading bacterium, MFKK-1, from seawater collected from a quay and investigated its PBSA degradation potential in the marine environment. The isolate, identified as a member of the genus Halopseudomonas, demonstrated PBSA degradation potential at the salinity levels of seawater. In addition to PBSA, the strain could degrade poly(ε-caprolactone) (PCL) and the aliphatic-aromatic polyester poly(butylene adipate-co-terephthalate) (PBAT). The strain used 1,4-butanediol and adipate, monomeric components of PBSA, as carbon sources for growth. Moreover, the gene aph_Hsp, responsible for the degradation of polyesters, was heterologously expressed in Escherichia coli. The purified recombinant APH_Hsp was characterized. This enzyme belongs to the α/β hydrolase family, with a catalytic triad composed of Ser₁₇₁, Asp₂₁₇, and His₂₄₉. It is a mesophilic enzyme that has shown the ability to degrade PBSA, PCL, and PBAT films in buffer supplemented with 0.5 M NaCl, a salinity comparable to that of seawater. Furthermore, the enzyme degraded amorphous poly(ethylene terephthalate) under 0.5 M NaCl conditions. The findings of this study enhance our knowledge of the microbial degradation of polyesters in marine environments, potentially supporting the sustainable application of biodegradable materials in ocean ecosystems.