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Degradation of polyvinyl chloride (PVC) microplastics employing the actinobacterial strain Streptomyces gobitricini
Summary
Researchers isolated a soil bacterium called Streptomyces gobitricini and tested its ability to break down PVC microplastics over 90 days. The bacterium achieved up to 66 percent weight reduction of the PVC particles and formed biofilms on the plastic surfaces. The study suggests that naturally occurring soil bacteria could potentially be harnessed for bioremediation of one of the most persistent and hazardous types of plastic waste.
The disposal of plastic materials has resulted in the huge increase of microplastics in the environment. One of the most hazardous plastic waste is polyvinyl chloride (PVC) due to its durability. A tool to remediate PVC microplastic polluted environment might be offered by microorganisms such as Actinobacteria, which has been proven to degrade PVC. Streptomyces gobitricini was isolated from soil polluted by heavy metals and plastic debris and used in a PVC microplastics degradation experiment. Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and scanning electron microscopy (SEM) were used to study the characteristics of microplastic particles. For the incubation, the optimal pH 7.5 was determined in a preliminary experiment where also pH 5.5 and pH 9.5 were included. Three PVC concentrations (200, 400, and 800 mg/L) were incubated in Luria-Bertani broth with S. gobitricini for 90 days. After the incubation, PVC-MP particles were recovered by filtering. The percentual weight loss of microplastics was highest (66%) in 200 mg/L treatment. Relatively high reductions were observed for the higher microplastic concentrations as well (400 mg/L; 65% and 800 mg/L; 60%). The bacterial growth decreased in order 200 mg/L (3.1 ± 0.1 CFU × 10/mL), 400 mg/L (3.0 ± 0.0 CFU × 10/mL) and 800 mg/L treatment (2.7 ± 0.0 CFU × 10/mL). High hydrophobicity was observed in all treatments at the end of the incubation indicating the formation of bacterial biofilm on the surfaces of plastic particles. The highest hydrophobicity (84%) associated with the bacterial strain was observed in 200 mg/L microplastics treatment. The results show that the bacterium S. gobitricini suits for further studies to reduce PVC microplastic waste in the environment.