A comprehensive approach to evaluate microplastic biodegradation potential of mangrove rhizobacteria

Aim: The study investigates the microplastic degradation potential of mangrove rhizobacteria and their efficiency as a consortium. Methodology: Rhizosphere sediments were collected from three common mangrove species, Avicennia sp., Acanthus sp. and Bruguiera sp. in Kerala, India. Rhizobacteria were isolated, characterized and a consortium was formulated, which were analyzed for the production of plastic-degrading enzymes. Structural changes in PVC microplastic films treated with individual cultures and consortium were determined by FTIR spectroscopy and Scanning Electron Microscopy. Results: The most abundant bacteria from each of the three mangrove species were identified as Priestia megaterium (SXC01) from Avicennia sp., Bacillus cereus (1MM03) from Acanthus sp. and Priestia megaterium (1MB38) from Bruguiera sp. Semi-quantitative and quantitative analysis showed that Priestia megaterium (SXC01) was efficient in the production of PEG dehydrogenase, Bacillus cereus (1MM03) in lipase production and Priestia megaterium (1MB38) in esterase and cutinase synthesis. Interestingly, the bacterial consortium showed higher production of enzymes and also exhibited greater stability in their attachment to the PVC surface compared to individual bacterial isolates. Further, FTIR spectral studies revealed pronounced vibrations in the hydroxyl (OH) regions, C-H regions and C-Cl stretching regions, providing evidence of bacterial PVC degradation. Interpretation: This study highlights the potential of consortium in the effective degradation of microplastics, surpassing individual isolates in enzymatic activity. To mitigate microplastic contamination, mangrove rhizobacteria are important players with potential uses in the restoration and maintenance of mangrove ecosystems. Key words: Bacterial consortium, Mangrove ecosystems, Microplastic degradation, Rhizobacterial strains