Microbial biodegradation of polypropylene microplastics: a comparative assessment of single- and dual-species models

Microplastics (MPs) are persistent environmentalpollutants with adverse effects on ecosystems and health. Microbial biodegradation is a promising remediation strategy, yet microbial efficiency varies based on species and experimental conditions. However, comparative studies evaluating the performance of single-species and dual-species degradation of polypropylene microplastics (PPMPs) remain limited. Therefore, the present study investigated the PPMP- degradation potential of Pseudomonas aeruginosa, Bacillus subtilis, and Lactobacillus plantarum in single- and dual-species systems over a 30-day incubation period under controlled conditions on PPMPs. Growth kinetics, weight loss, FTIR spectroscopy, SEM imaging, and GC-MS analysis were employed to assess microbial degradation of PPMPS. The results demonstrated significant MP degradation in the presence of all bacterial species, with the dual-species model showing enhanced degradation efficiency compared to individual strains. Single-species degradation yielded 28.6% weight loss of MP for P. aeruginosa, 12% for B. subtilis, and 16% for L. plantarum. Dual-species models achieved 49% weight loss in P. aeruginosa and B. subtilis, 32% in B. subtilis and L. plantarum, and 20% in L. plantarum and P. aeruginosa, indicating higher polymer breakdown in the dual-species model. FTIR spectra revealed chemical modifications indicative of polymer oxidation, increased transmittance, e.g., 2978 cm^-1 (C-H alkane, up to 101%), 1735 cm^-1 (C=O carbonyl), 3657 cm^-1 (O-H), new peaks like 1450 cm^-1 (C-H bend). SEM imaging confirmed microbial colonisation, biofilm formation, and structural deterioration of PPMP surfaces. GC-MS analysis identified degradation byproducts, including monomers, acids, esters, and additives, confirming microbial catabolism of PPMPs. This study highlights the effectiveness of microbial biodegradation and underscores the potential of microbial consortia for MP remediation.