Microbial diversity and enzymatic potential for plastic degradation in contaminated dumpsites in Mazamitla, Jalisco

Plastic pollution has become an important global environmental concern, emphasizing the urgent need for effective plastic degradation strategies. Microorganisms have demonstrated potential in degrading plastics through enzymatic activities. This study investigated the microbial diversity and enzymatic potential of microorganisms isolated from plastic-contaminated dumpsites located in Mazamitla, Jalisco a west-central region of Mexico. Microbial diversity was assessed through metataxonomic analysis based on 16S rRNA gene sequencing of DNA extracted from soil samples. A total of 946 genera across 49 phyla were identified, with Actinobacteria, Pseudomonadota, Bacillota, Bacteroidota, and Acidobacteria as the most dominant, while at genus level, Pseudomonas, Bacillus, and Streptomyces were the most representative. Culturable microorganisms were isolated, identified, and screened from soil samples for enzymatic activities associated with plastic degradation. From these, 280 mesophilic isolates were recovered, of which 251 were successfully identified. Among them, 94 % belonged to the domain Bacteria, primarily from the phyla Bacillota and Pseudomonadota. The remaining 6 % of isolates were fungi from the phylum Basidiomycota. During agar-based functional enzymatic screening using mineral oil as an inducer, Serratia marcescens demonstrated the highest extracellular carboxylesterase activity (240.3 ± 11.0 U/L), Comamonas testosteroni (193.9 ± 2.5 U/L), and Pseudomonas koreensis (180.4 ± 8.0 U/L) exhibited significant esterase/lipase activities. C. testosteroni (125.6 ± 15.5 U/L), Chryseobacterium joostei (125.1 ± 14.2 U/L), and Bacillus mycoides (120.6 ± 9.9 U/L) were the most active for cutinase activity. Lelliottiaamnigena, S. marcescens, Pseudomonaschlororaphis, and Pseudomonaskilonensis exhibited the highest growth using plastics as the sole carbon source. These results highlight the metabolic diversity and enzymatic capabilities of microorganisms in plastic-contaminated soils, identifying promising candidates for sustainable plastic waste management.