Achromobacter xylosoxidans as a new microorganism strain colonizing high-density polyethylene as a key step to its biodegradation

Abstract

This study presents results of research on isolation new bacteria strain Achromobacter xylosoxidans able to effect on the structure of high-density polyethylene (HDPE), polymer resistant to degradation in environment. New strain of A. xylosoxidans PE-1 was isolated from the soil and identified by analysis of the 16S ribosome subunit coding sequences. The substance to be degraded was HDPE in the form of thin foil films. The foil samples were analyzed with Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) as well as scanning electron microscope (SEM), and the results revealed degradation of chemical structure of HDPE. About 9 % loss of weight was also detected as a result of A. xylosoxidans PE-1 effect on HDPE foil. On the basis of comparative spectral analysis of the raw material before the bacteria treatment and the spectrum from a spectra database, it was assumed that the HDPE was the only source of carbon and energy for the microorganisms. No fillers or other additives used in the plastic processing were observed in HDPE before experiments. This is the first communication showing that A. xylosoxidans is able to modify chemical structure of HDPE, what was observed both on FTIR, in mass reduction of HDPE and SEM analysis. We also observed quite good growth of the bacteria also when the HDPE was the sole carbon source in the medium. These results prove that A. xylosoxidans is an organism worth applying in future HDPE biodegradation studies.

Keywords: Biodegradation; FTIR; HDPE; Microorganisms; Polymers; SEM.

Fig. 1

OD₆₅₀ values for modified medium Davis Minimal Broth 1, 2 without glucose and 3, 4 supplemented with glucose assays

Fig. 2

HDPE foil film colonized with A. xylosoxidans on Davis Minimal Broth without glucose (HDPE as sole source of carbon) 3 days after bacteria inoculation to the medium

Fig. 3

Percentage mass reduction of HDPE film after 150 days of incubation in modified Davis Minimal Broth medium

Fig. 4

Spectra of samples collected from 1 and 2 assays without glucose and 3, 4 assays supplemented with glucose. Origin of bands: a −OH group, b −C-H group, c >C = O group, d −C-H group, e −C-O-O group, f, h >CH₂ skeletal vibrations, g >CH₂ group

Fig. 5

Final spectra of representative degraded samples in comparison to control samples, without glucose (sample 25 and control, a) and with addition of 30 % of recommended amount of glucose (sample 28 and control, b). Origin of bands: a −OH group, b −C-H group, c >C = O group, d −C-H group, e −C-O-O group, f, h >CH₂ skeletal vibrations, g >CH₂ group

Fig. 6

Representative SEM photographs (magnification 2000×) of untreated model virgin HDPE film sample (M) and subjected to A. xylosoxidans PE-1 activity (A-C) after 150 days of incubation