Enhanced polymer degradation of polyethylene and polypropylene by novel thermophilic consortia of Brevibacillus sps. and Aneurinibacillus sp screened from waste management landfills and sewage treatment plants

The current study prioritizes the polymer degradation potential of novel thermophilic consortia of Brevibacillus sps. and Aneurinibacillus sp. screened from sewage treatment plants and waste management landfills for low and high density polyethylene (LDPE, HDPE) and polypropylene (PP) films and pellets. The screening of 36 plastic degrading isolates was carried out and degradation abilities were studied for 140 days. The eight isolates that showed highest percentage degradation were combined in various possible combinations to study the degradation efficiency. Among them, the combination of IS1, IS3, ISA and ISC demonstrated highest percentage weight reduction for three forms of plastic which was selected for further degradation study at varying temperature conditions. The biodegradation end products post 140 days were studied by Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), nuclear magnetic resonance (NMR) and gas chromatography-mass spectroscopy (GC-MS). The isolates were characterized by 16S rDNA gene sequencing and secondary structures of 16S rDNA were predicted. The highest percentage weight reduction for LDPE, HDPE and PP strips treated with the consortia of four isolates was determined to be 58.21 +/- 2, 46.6 +/- 3 and 56.3 +/- 2% respectively and LDPE, HDPE and PP pellets that were treated with consortia was determined to be 45.7 +/- 3, 37.2 +/- 3 and 44.2 +/- 3% respectively (p <= 0.05) at 50 degrees C in comparison with other combinations and varying temperatures. FTIR analysis of the plastic film post 140 days showed that the presence of new adsorption bands. SEM and AFM analysis revealed that biofilm formation and structural variations on the treated plastic strips and EDS analysis suggested significant reduction in percentage weight of carbon content. NMR analysis suggested the appearance of methyl and aldehyde moieties and GC-MS analysis revealed fatty acid end-products. IS1, IS3, ISA and ISC were found to be four novel strains and were designated as Aneurinibacillus aneurinilyticus btDSCE01, Brevibacillus agri btDSCE02, Brevibacillus sp. btDSCE03 and BrevibaciUus brevis btDSCE04 respectively. The study suggested that these novel thermophilic consortia can be scaled up as potential inoculums for the enhanced biodegradation of polyethylene and polypropylene derivatives in plastic wastes.