Degradation of poly(epsilon-caprolactone) by a thermophilic bacterium Ralstonia sp strain MRL-TL isolated from hot spring

作者：Shah Aamer Ali^*; Nawaz Ahmed; Kanwal Lubna; Hasan Fariha; Khan Samiullah; Badshah Malik

来源：International Biodeterioration & Biodegradation, 2015, 98: 35-42.

DOI：10.1016/j.ibiod.2014.11.017

• Poly(epsilon-caprolactone)
• Ralstonia sp.
• Biodegradation
• PCL depolymerase
• Column chromatography

A thermophilic bacterium, designated as strain MRL-TL was isolated from hot water spring that could degrade poly(epsilon-caprolactone) (PCL). The bacterium was identified as Ralstonia sp. strain MRL-TL by 165 rRNA gene sequencing. The results of scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy indicated the degradation of PCL by strain MRL-TL. The degradation of PCL in nature is attributed to microorganisms that secrete extracellular PCL depolymerases. PCL depolymerase was purified to homogeneity by column chromatography, as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and molecular weight was found to be approximately 50 kDa. The enzyme preferred substrate among p-nitrophenyl acyl esters was p-NP-caproate (C-6), indicating that the enzyme is an esterase rather than a lipase. The enzyme was stable at 37 degrees C-55 degrees C (with an optimal temperature 50 degrees C) and in a pH range of 6.0-8.0 (with an optimal pH of 7.0). It was stable in the presence of various metal ions, inhibitors and surfactants. Phenylmethyl sulphonyl fluoride (PMSF) inhibited enzyme activity, which indicates that this enzyme belongs to the serine hydrolase family like other PHA depolymerases. The enzymes from MRL-TL could degrade various aliphatic polyesters; therefore, it might be applied for bioremediation in the polyesters-contaminated environments.

• 出版日期2015-3