Analysis of Bacterial Isolates Capable of Partially Degrading Polyethylene Terephthalate

Abstract

In this work, we studied 46 bacterial isolates to determine their potential for polyethylene terephthalate (PET) degradation. Only eight lipase-positive isolates were pre-selected to continue analysis. The isolates belonged to the genera Micrococcus, Acinetobacter, Pseudomonas, Bacillus, and Pseudochrobactrum. In addition to lipase, other enzymatic activities such as protease, carboxymethyl cellulase, xylanase, and chitinase were detected. PET sheets were pretreated with temperature, UV light, HNO₃, and Stenotrophomonas pavanii. All isolates were tested against pretreated PET for 60 days. All isolates displayed lipase activity, and some hydrolase activities. The chemical changes of PET sheets were determined using Fourier-transform infrared spectroscopy. Peaks observed at 3000-3500 cm-1 corresponding to hydroxyl group suggested degradation. The physical changes of PET observed with the naked eye and with SEM consisted of erosion, bubbles, scales, bumps, pits, and a shiny surface. Pseudomonas soli was selected as the best PET degrader, according to the notable changes in the infrared spectrum and macroscopic changes compared to the other genera and the control. In addition, this isolate did not show xylanase activity and it lacks the chitinase gene too. It is possible that not only lipase activity could be associated with the PET degradation, but also another enzymatic activity not detected in this study. Although the genus Pseudomonas has been reported as a plastic degrader, the P. soli species is novel in the degradation of PET, as well as the other genera mentioned here. Finally, these findings contribute to the knowledge of bacterial species for PET degradation.

Keywords:
PET; hydrolases; degradation; lipases; Pseudomonas; Bacillus

HIGHLIGHTS

Eight bacterial isolates from five genera were positive to lipase test.

Eight bacterial isolates were tested against pretreated PET for 60 days.

Bacterial degradation in PET was detected by FT-IR and SEM.

Pseudomonas soli was selected as the best PET degrader.