Degradation of newly developed date palm agro-residues-filled polyethylene biocomposites in the planktonic and benthic zones of a marine environment

Although biodegradable polyethylene (PE)-based biocomposites reinforced using date palm fibers have emerged as an eco-friendly alternative to minimize plastic pollution, not much is known regarding their degradability especially in the marine environment. Our study aimed at developing date palm- and cellulose-based PE biocomposite panels (DPE and CPE, respectively), testing their biodegradability in planktonic and benthic marine habitats, and examining the associated bacterial community and its possible role in biodegradation. Mechanical, physical, chemical, and thermal properties of biocomposites were characterized using tensile and flexural tests, crystallinity and water absorption tests, fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA), respectively. Fabricated DPE panels demonstrated increased flexural attributes, and overall physical/structural integrity reflecting an improved mechanical sustainability than PE. Post-immersion, all panels revealed biotic rather than abiotic degradation of both PE matrix and date palm or cellulose. This was mainly evident from significant reductions in flexural strength, density, and intensity of PE-specific FTIR peaks. A mature biofouling community was developed on DPE and CPE based on the total biomass, bacterial, and phototroph abundances analyses. Non-metric multidimensional scaling (NMDS) analysis of the MiSeq dataset revealed habitat- rather than substrate-specific clustering of the bacterial community. Major bacterial groups detected included alpha- and gamma-proteobacteria, Clostridia, and Bacilli. Although certain genera such as Psychrobacter, Pseudomonas, and Bacillus were previously reported to play a major role in PE degradation, their degradation mechanisms remain unclear till date. We conclude that the newly designed biocomposites can potentially replace conventional materials, since they are derived from natural resources and biodegradable.