Degradation of polyester polyurethane by newly isolatedPseudomonas aeruginosa strain MZA-85 and analysis of degradation products by GC–MS
Ziaullah Shah, Fariha Hasan, Lee Krumholz, Deniz Fulya Aktas, Aamer Ali Shah
Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan.
In this report, a polyester polyurethane (PU) degrading bacterium, designated as strain MZA-85, was isolated from soil through enrichment. The bacterium was identified through 16S rRNA gene sequencing; it was completely matched with Pseudomonas aeruginosa type strain. The degradation of PU film pieces by P. aeruginosa strain MZA-85 was investigated by scanning electron microscopy (SEM), Fourier transformed infra-red spectroscopy (FT-IR) and gel permeation chromatography (GPC). SEM micrographs of PU film pieces, treated with strain MZA-85, revealed changes in the surface morphology. FTIR spectrum showed increase in organic acid functionality and corresponding decrease in ester functional group. GPC results revealed increase in polydispersity, which shows that long chains of polyurethane polymer are cleaved into shorter chains by microbial action. The bacterium was found to produce cell associated esterases based onp-Nitrophenyl acetate (pNPA) hydrolysis assay. 1,4-Butanediol and adipic acid monomers were detected by gas chromatography–mass spectrometry (GC–MS), which were produced as a result of hydrolysis of ester linkages in PU by cell bound esterases. Strain MZA-85 not only depolymerized PU but also mineralized it into CO2and H2O, as indicated by increase in cells growth in the presence of degradation products as well as detection of CO2 evolution through Sturm test. From the results presented above, it is finally concluded thatP. aeruginosa strain MZA-85, as well as its enzymes, can be applied in the process of biochemical monomerization for the pure monomers recycling.
Keywords:Polyester polyurethane, Biodegradation, Pseudomonas aeruginosa, Scanning electron microscopy, Fourier transformed infra-red spectroscopy, Sturm test, Gas chromatography–mass spectrometry.