Biodeterioration of Untreated Polypropylene Microplastic Particles by Antarctic Bacteria

Abstract

Microplastic pollution is globally recognised as a serious environmental threat due to its ubiquitous presence related primarily to improper dumping of plastic wastes. While most studies have focused on microplastic contamination in the marine ecosystem, microplastic pollution in the soil environment is generally little understood and often overlooked. The presence of microplastics affects the soil ecosystem by disrupting the soil fertility and quality, degrading the food web, and subsequently influencing both food security and human health. This study evaluates the growth and biodegradation potential of the Antarctic soil bacteria Pseudomonas sp. ADL15 and Rhodococcus sp. ADL36 on the polypropylene (PP) microplastics in Bushnell Haas (BH) medium for 40 days. The degradation was monitored based on the weight loss of PP microplastics, removal rate constant per day (K), and their half-life. The validity of the PP microplastics' biodegradation was assessed through structural changes via Fourier transform infrared spectroscopy analyses. The weight loss percentage of the PP microplastics by ADL15 and ADL36 after 40 days was 17.3% and 7.3%, respectively. The optimal growth in the BH media infused with PP microplastics was on the 40th and 30th day for ADL15 and ADL36, respectively. The infrared spectroscopic analysis revealed significant changes in the PP microplastics' functional groups following the incubation with Antarctic strains.

Keywords: Pseudomonas sp.; Rhodococcus sp.; plastic pollution; polypropylene; pristine fellfield soil.

Figure 1

Changes in cultures of the Antarctic bacteria Pseudomonas sp. ADL15 and Rhodococcus sp. ADL36 during 40 days of incubation in Bushnell Haas (BH) media infused with polypropylene (PP) microplastics: (a) optical density, (b) microbial counts, (c) relative weight loss of PP microplastics, and (d) pH of the media. Data represent mean ± SD, n = 3.

Figure 2

The Fourier transform infrared (FTIR) spectrum of polypropylene (PP) microplastics: (a) before incubation with bacteria, (b) after 40 days of incubation with Pseudomonas sp. ADL15, and (c) after 40 days of incubation with Rhodococcus sp. ADL36.