Isolation and MALDI–TOF MS‑based identification of new bacterial isolates from greenhouse and mulch film fields in Izmir (Turkiye) for LDPE biodegradation

Low density polyethylene (LDPE) plastic films, which are widely used in greenhouses and mulch areas in the agricultural sector, can remain in the environment for a long time due to their resistance to decomposition structures and create large amounts of plastic pollution. In this study, it was aimed to isolate and identify bacteria which are capable of polyethylene (PE) degradation from greenhouse and mulch film soils containing plastic wastes in Izmir, one of the cities where greenhouse farming is most common in Türkiye, and to determine the degradation potentials of these bacteria. Bacteria were screened in soil samples taken from different greenhouses, mulched film areas and garden areas containing plastic waste, which have been covered with PE film for 10-30 years. Eight bacterial isolates were identified for the first time from these areas using the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) system. Plastic degradation properties of bacterial isolates were demonstrated after 30-days degradation study by reduction in PE film weight, FTIR-ATR analysis to determine structural changes on these films and SEM imaging to visualize changes in surface morphology. It was determined that the reduction rates in PE film weights of individual bacterial isolates after 30 days varied between 25.39 and 7.08%, and the highest weight loss was recorded in Acinetobacter pittii HAT01. Also, the bacterium was observed to have biofilm formation capacity. FTIR-ATR analysis and SEM imaging findings of PE films supported the weight loss findings. This study provides new candidate strains adapted to long-term LDPE-contaminated agricultural soils and contributes to the development of sustainable biodegradation strategies.