Hydrocarbon-based plastics: Progress and perspectives on consumption and biodegradation by insect larvae.

The obvious contrast between the remarkable durability and the high consumption of plastic products leads to the deposition of at least 100 million tons of plastics per year in nature. Since 2010, several studies have shown the potential of insect larvae to biodegrade different types of plastics, at higher rates than those reported for microorganisms. This review discusses a compilation of studies about the consumption and biodegradation of hydrocarbon-based plastics, particularly PE, PS, PP and PVC, by lepidopteran and coleopteran larvae. Insects of the Coleoptera order seem to have a better adaptation for PS biodegradation, while those of the Lepidoptera order can better biodegrade PE. Tenebrio molitor biomineralize PE and PS into CO2, and PVC into HCl; while Tenebrio obscurus and Zophobas atratus converts PE and PS into CO2, respectively. Plastic biodegradation by T. molitor has been shown to be dependent on microbiota, exception for PE. Similar PS and PE biodegradation profile has been shown for T. obscurus. PS, PP and PE biodegradation by Z. atratus is also reported to be microbial-dependent. For Galleria mellonella, microbial role on PE biodegradation is still controversial, but the PS metabolism was proved to be microbiota-independent. Advances in this field has stimulated new studies with other insect species, which need to be better explored. Uncovering and understanding the chemical processes behind the innate plastic biodegradation by insect larvae will open the perspective to new eco-friendly innovative biotechnological solutions for the challenge of plastic waste.

Toxicological evaluation of the herbicide Palace® in Drosophila melanogaster.

Drosophila melanogaster is a suitable model for toxicological studies of environmental pollutants including pesticides, which are known to produce adverse effects on the ecosystem. The aim of the present study was to investigate the adverse influence of the pesticide Palace®, a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D) and picloram, using D. melanogaster as a model organism. D. melanogaster larvae were exposed to 0.011%, 0.022%, 0.112%, 0.224%, and 1.12% of Palace® and development examined. Adult flies were treated with 0.224%, 1.12%, 2.24%, 11.2%, and 22.4% of Palace® and the following analyzed survival, locomotor behavior, acetylcholinesterase (AchE) activity, reactive oxygen species (ROS) production, total and non-protein thiol levels, and mitochondrial function. Data demonstrated that exposure of flies during larval stage to Palace® significantly affected development of larvae to the adult stage. In adults, treatment with Palace® resulted in dose-dependent progressive adverse effects on survival and behavior with males more sensitive than females. In both males and females, ROS production and AchE activity were not markedly affected by Palace®. However, total thiol levels increased in female heads treated with highest dilution of Palace®, while decreased levels of non-protein thiols were detected in heads of male flies following Palace® exposure. In females and males flies exposed to Palace® reduced mitochondrial oxygen consumption related to oxidative phosphorylation (OXPHOS) state, mitochondrial capacity of excess (E-P) and respiratory control ratio (RCR) was noted, indicating that the pesticide mixture altered mitochondrial complexes functionality with consequences on bioenergetics. In summary, Palace® exposure produced adverse effects on D. melanogaster affecting survival, development, behavior and mitochondrial function, which may exert ecotoxicological consequences which poses risks to different organisms in the ecosystem.

Weathering Resistance of Waterborne Polyurethane Coatings Reinforced with Silica from Rice Husk Ash.

Waterborne polyurethanes (WPUs) are interesting materials for coatings when compared to solvent-based polyurethanes, once that reducing the concentration of volatile organic compounds that are harmful for human health and the environment. However, the WPU has low weathering resistance. In order to improve this behavior among others properties, inorganic fillers has been added in these systems. SiO2 particles from various sources, mainly, from agro-industrial waste, as rice husk has attracted the scientific and technological interest. In this study, the accelerated weathering essay was performed in waterborne polyurethane (WPU)/ silica (from rice husk ash) composites in order to evaluate the thermal and physical changes in these materials. These composites were prepared by two distinct methods: in situ polymerization and blending method. The highest resistance to thermal degradation and to accelerated weathering was reached with WPU/silica composites obtained by blending method due the interactions between SiO2 particles and the polymer matrices. Blending method for preparation WPU/silica composites proved to be a simpler and faster method, with no drawback for large scale application.