Degradation of Polylactic Acid (PLA) by Microorganisms Recovered from Buried PLA/Wood Composite Forestry Containers in the Biobío Region, Chile

The environmental impact of petroleum-derived plastics has stimulated the development of biodegradable alternatives such as polylactic acid (PLA), a renewable polymer increasingly used in biodegradable nursery containers in the forestry sector. However, PLA degradation in natural soil environments remains relatively slow, highlighting the need to better understand the microorganisms involved in this process. In this study, we investigated the diversity and biodegradation potential of cultivable PLA-degrading bacteria recovered from buried PLA/wood composite forestry containers in the Biobío Region, Chile. The containers were buried for one year in trumao and granitic soils, and microorganisms recovered from the containers were screened for their ability to degrade PLA. Three bacterial strains (5, 12, and 16) exhibiting PLA-degrading activity were isolated. PLA depolymerization was observed in the presence of gelatin under the experimental conditions. Taxonomic analyses identified strain 5 as belonging to the genus Amycolatopsis, whereas strains 12 and 16 were assigned to the genus Bacillus. PLA degradation assays using PLA films over a 14-day period revealed distinct degradation behaviors among the isolates. Strain 5 showed the greatest film weight loss (37.00 ± 0.20 mg), whereas strain 16 produced the largest reduction in PLA molecular weight, indicating a higher depolymerization potential. SEM observations further confirmed surface alterations of the polymer after incubation with the isolates. These results demonstrate that forest soils harbor bacteria capable of degrading PLA under laboratory conditions and highlight strain 16 as a promising candidate for future studies on PLA-degrading enzymes and biotechnological applications.