Prospection of microbial enzymes for plastic biodegradation from plastic dumped soil in Tepic, Nayarit, Mexico

Abstract

The environmental impact of plastics has motivated the search for biotechnological strategies for their degradation. This study isolated and characterized microorganisms with hydrolytic and oxidoreductase enzymatic activity from a contaminated site in Nayarit, Mexico, called Arena Cora. 23 plastic waste samples were collected, isolating 172 strains. A preliminary screening of halo formation in a solid medium at 30°C for 48h was performed to identify extracellular enzymes, followed by quantification through submerged fermentation at 30°C, 150 rpm for 72h, both with inducers. Identification was carried out using MALDI-TOF mass spectrometry. The enzymatic screening in solid medium identified 22 strains with relevant activity, with Bacillus (76.4%) and Pseudomonas (11.8%) being the most prevalent genera. The most frequent activities were esterase/lipase and hydrolase, with 48 and 34 positive strains, respectively. 6.4% of these strains reached the highest activity levels. Furthermore, five strains with cutinase activity and 15 with laccase activity were identified. Submerged fermentation confirmed the production of hydrolytic and oxidoreductase extracellular enzymes. B. subtilis (A55A) exhibited the highest induced activity with tributyrin and mineral oil, reaching over 120 U/mL at 24h. B. cereus (A41C) showed the highest cutinase activity (17.05 U/mL at 72h). The highest laccase production was observed in strain A46E (10.3 U/mL at 72h). P. koreensis (A58F), with no prior records of plastic degradation, displayed lipase activity at 24h. These results highlight the potential of native microorganisms in plastic biodegradation and their potential application in bioremediation strategies.