Polystyrene microplastic degradation by a novel PGPR Bacillus spizizenii

Area of Science:

• Environmental Microbiology
• Bioremediation
• Polymer Science

Background:

• Plastic pollution, particularly microplastics (MPs), poses a significant environmental threat.
• Polystyrene (PS) is a common plastic polymer that is persistent and difficult to degrade.
• Bioremediation using microorganisms offers a sustainable approach to plastic waste management.

Purpose of the Study:

• To investigate the potential of Bacillus spizizenii, a plant growth-promoting rhizobacterium (PGPR), for degrading polystyrene microplastics (PS-MPs).
• To evaluate the efficiency and mechanisms of PS-MP degradation by Bacillus spizizenii.
• To assess the plant growth-promoting traits of the bacterium for potential soil restoration applications.

Main Methods:

• Cultivation of Bacillus spizizenii with Polystyrene (PS) as the sole carbon source.
• Quantification of PS-MP degradation efficiency over 30 days.
• Analysis of chemical structure changes using Fourier Transform Infrared Spectroscopy (FTIR).
• Visualization of surface morphology changes using Scanning Electron Microscopy (SEM).
• Metabolic profiling using Gas Chromatography-Mass Spectrometry (GC-MS) to infer degradation pathways.
• Confirmation of plant growth-promoting traits (IAA production, phosphate solubilization, ammonia, HCN, siderophore production).

Main Results:

• Bacillus spizizenii achieved an 85.86% degradation efficiency of PS-MPs within 30 days.
• FTIR analysis confirmed significant alterations in PS-MP peak intensities, indicating chemical breakdown.
• SEM imaging revealed clear surface degradation of PS-MPs.
• GC-MS metabolic data, when cross-referenced with the KEGG database, suggested potential degradation pathways.
• The bacterium exhibited key PGPR traits, including Indole Acetic Acid (IAA) production, phosphate solubilization, ammonia, Hydrogen Cyanide (HCN), and siderophore production.

Conclusions:

• Bacillus spizizenii is a highly effective agent for the degradation of polystyrene microplastics.
• The bacterium's ability to degrade PS-MPs and its PGPR characteristics make it a promising candidate for bioremediation of plastic-contaminated soils.
• This study presents a novel biological solution for addressing polystyrene pollution.