Recently, the contribution of earthworms to plastic degradation and their capability to swallow smaller plastic fragments, known as microplastics, has been emphasized. The worm physically changes the size of microplastics and enhances microbial activities to increase the possibility of degradation. However, no research has shown that earthworms can chemically degrade microplastics to an element form, CO₂ or H₂O. In this review, previous research has been thoroughly explored to analyse the role that earthworms could play in plastic degradation in the soil. Earthworms can significantly affect the physical characteristics of plastics. However, earthworms’ abilities to chemically degrade or change the chemical structure of plastics and microplastics have not been observed. Additionally, earthworms exhibit selective feeding behaviour, avoiding areas containing a high plastics concentration and rejecting plastics. Consequently, earthworms’ abilities to adapt to the microplastics in soil in the environment can cause a problem. Based on this review, the challenges faced in earthworm application for plastic degradation are mostly expected to be associated with the toxicity and complexity of the plastic material and environmental factors, such as the moisture content of the soil and its temperature, microbial population, and feeding method.

Although numerous studies have demonstrated the benefits of incorporating filler particles into maxillofacial silicone elastomer (MFPSE), a review of the types, concentrations and effectiveness of the particles themselves was lacking. The purpose of this systematic review and meta-analysis was to review the effect of different types of filler particles on the mechanical properties of MFPSE. The properties in question were (1) tensile strength, (2) tear strength, (3) hardness, and (4) elongation at break. The findings of this study can assist operators, technicians and clinicians in making relevant decisions regarding which type of fillers to incorporate based on their needs. The systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 26 original articles from 1970 to 2019 were selected from the databases, based on predefined eligibility criteria by two reviewers. The meta-analyses of nine papers were carried out by extracting data from the systematic review based on scoring criteria and processed using Cochrane Review Manager 5.3. Overall, there were significant differences favoring filler particles when incorporated into MFPSE. Nano fillers (69.23% of all studies) demonstrated superior comparative outcomes for tensile strength (P < 0.0001), tear strength (P < 0.00001), hardness (P < 0.00001) and elongation at break (P < 0.00001) when compared to micro fillers (30.76% of all studies). Micro fillers demonstrated inconsistent outcomes in mechanical properties, and meta-analysis of elongation at break argued against (P < 0.01) their use. Current findings suggest that 1.5% ZrSiO₄, 3% SiO₂, 1.5% Y₂O₃, 2–6% TiO₂, 2–2.5% ZnO, 2–2.5% CeO₂, 0.5% TiSiO₄ and 1% Ag-Zn Zeolite can be used to reinforce MFPSE, and help the materials better withstand mechanical degradation.

The suitability of bacteria application as fillers to reinforce calcium chloride cured sodium alginate film was investigated through the determination of the physical, morphological and mechanical properties of composite films. There were six species of bacteria isolated from palm oil mill effluent sample. The bacteria sample selected for filler reinforcement has a sub-micron diameter of 0.83 ± 0.13 µm. The growth curve of selected bacteria revealed that four days of broth culture produced the maximum bacteria mass. The composite films were produced with reinforcement of 0.1 g, 0.2 g, 0.3 g and 0.4 g of bacteria respectively. Overall, the increment of bacteria mass resulted in the production of yellowish composite films with improved morphological, physical and mechanical properties. The results revealed that the composite films reinforced with 0.3 g and 0.4 g of bacteria appeared to have less curling on the surface of the film. The water absorption properties of the films were initially 140.74% and remained constant at an approximate of 200% after the reinforcement. The tensile strength properties showed a total increment of approximately 22.70% (from 36.10 ± 1.94 MPa to 44.29 ± 0.60 MPa). Based on the results, bacteria fillers were not able to enhance the elongation properties because only about 0.6% of overall increment was observed which was considered insignificant. It was concluded that the bacteria biomass has the potential to be used as fillers to reinforce calcium chloride cured sodium alginate film.