Assessing the Biodegradation of Low-Density Polyethylene Films by Candida tropicalis SLNEA04 and Rhodotorula mucilaginosa SLNEA05

Environmental pollution resulting from the accumulation of plastic waste poses a major ecological challenge. Biodegradation of these polymers relies on microorganisms capable of decomposing them, generally through the biodeterioration, biofragmentation, assimilation, and mineralization stages. This study evaluates the contribution and efficacy of indigenous soil yeasts isolated from a northeastern Algerian landfill in degrading low-density polyethylene (LDPE) plastic bag films. Candida tropicalis SLNEA04 and Rhodotorula mucilaginosa SLNEA05 were identified through internal transcribed spacer (ITS) and large subunit ribosomal RNA gene sequencing. These isolates were then tested for their ability to biodegrade LDPE films and utilized as the sole carbon source in vitro in a mineral salt medium (MSM). The biodegradation effect was examined using scanning electron microscopy (SEM), attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, and X-ray diffraction (XRD). After 30 days of incubation at 25 °C, a significant weight loss was observed compared to the control for both cultures: 7.60% and 5.53% for C. tropicalis and R. mucilaginosa, respectively. SEM analysis revealed morphological alterations, including cracks and holes, ATR-FTIR detected new functional groups (alcohols, alkynes, aldehydes, alkenes and ketones), while XRD identified changes in the polymer crystallinity and phase composition. These findings underscore the potential of the two yeast isolates in LDPE biodegradation, offering promising insights for future environmental applications.