LPDE biodegradation promoted by a novel additive based on silica nanoparticles: Structural, microbial and ecotoxicological characterization.

Abstract

This study developed a biodegrading additive based on nanosilica and modified by cellulase enzyme in the presence of citric acid and sodium citrate. The additive was tested as a facilitator for biodegradation of the commercial low-density polyethylene (LDPE) in soil. Enzyme immobilization was confirmed by enzymatic assays. Moreover, additive and nanocomposites were characterized by spectroscopic and microscopic techniques. To assess the role of additive in biodegradation, CO₂ production in soil was measured at 30 °C for 83 days. Biodegraded nanocomposites were cultivated to isolate possible LDPE-biodegrading microorganisms. Ecotoxicity of the studied materials was evaluated on cucumber (Cucumis sativus L.). CO₂ production from LDPE/additive sample was similar to the starch (1055 ± 14 mg and 1078 ± 28 mg, respectively), and higher than pure LDPE (882 ± 34 mg) and LDPE/nanosilica (992 ± 30 mg). Although the presence of LDPE/nanosilica and LDPE/additive led to root length reduction of 24.3 ± 2.3% compared to the control (soil), the accumulation of root biomass was not affected. Furthermore, the nanocomposites did not cause harmful effects on seedling growth. Nine microbial isolates were recovered from biodegraded samples and identified by molecular techniques. It was demonstrated for the first time the LDPE biodegradation potential by four bacterial isolates (Bacillus safensis FO-36b, Lysinibacillus capsici, Bacillus albus N35-10-2 and Bacillus paranthracis Mn5) and two fungal isolates (Cladosporium halotolerans clone EF_526 and Cladosporium sp. MV-2018B isolate MLT-27). Our study sheds light on the biodegradation of commercial LDPE by soil microorganisms using a novel LDPE-biodegrading additive nanocomposite.