Contribution of Eisenia andrei earthworms in pathogen reduction during vermicomposting

Earthworm activity reduces bacterial pathogen loads in sewage sludge

Wastewater processing plants (WWTPs) produce large amounts of sewage sludge that are mainly disposed of on the land. This represents a health hazard due to the high loads of human bacterial pathogens (HBPs) the sludge generally contains. Vermicomposting, a mesophilic process, can reduce HBPs in organic wastes. This raises the question as to how earthworms eliminate HBPs. We aimed to determine whether earthworms reduce the levels or eliminate HBPs from sewage sludge and to establish whether the reduction/elimination occur during active (earthworm casts) or maturation (vermicompost) stages of vermicomposting. To this end, we analyzed HBPs (Escherichia coli O157, Listeria monocytogenes, Salmonella spp., and total E. coli) in sewage sludge samples from three WWTPs and the fresh earthworm casts and vermicomposts by using qPCR, to assess the impact of earthworms on reducing and/or eliminating HBPs. We did not detect either Salmonella spp. nor E. coli O157 in any of the samples. Earthworms removed or significantly reduced the amounts of E. coli and L. monocytogenes (mean relative abundances of 2.4 × 10-7 and 1.5 × 10-8 respectively) in the sewage sludge. Thus, the abundance of these HBPs was lower (or not present) in casts than in sewage sludge. This was also observed in vermicomposts (95% and 43% reduction in E. coli abundance in casts and vermicompost, respectively). Finally, our findings indicate that vermicompost derived from sewage sludge meets the requirements of organic fertilizers at least regarding the microbial pathogen content. Thus, vermicomposting seems to be a promising technique for managing municipal waste.

Changes in the content of emerging pollutants and potentially hazardous substances during vermi/composting of a mixture of sewage sludge and moulded pulp

Processing sewage sludge can be problematic due to its potential environmental toxicity. It may contain high concentrations of pharmaceuticals, polycyclic aromatic hydrocarbons, and heavy metals, as well as pathogenic microorganisms. However, it is a good source of organic matter and rich in microbial communities and enzymatic activity. This study deals with composting and vermicomposting of pre-composted mixtures of two different kinds of sewage sludge blended with moulded pulp in an operating composting plant. Of the total number and concentration of pollutants detected in individual piles, a large percentage of them were reduced by the composting process. The composting 2 process resulted in the greatest reduction in contaminating substances--a total of 19 substances by 4.39-90.4%. Some pharmaceuticals accumulated in earthworm bodies during vermicomposting; a total of 11 substances were detected. Atorvastatin showed the highest percentage reduction in compost 2 (90.4%), vermicompost 1 (65.2%) and vermicompost 2 (97.3%). Both composting and vermicomposting appeared to be effective for removal of heavy metals. A higher content of microbial phospholipid fatty acids (PLFAs) was found in composts than vermicomposts. There was a significant reduction in the content of pathogenic microorganisms in both processes, but the reduction in enterococci was not significant.

Assessing quality and beneficial uses of Sargassum compost

Sargassum spp. (specifically Sargassum fluitans and S. natans), one of the dominant forms of marine macroalgae (seaweed) found on the beaches of Florida, is washing up on the shores throughout the Caribbean in record quantities. Currently, a common management option is to haul and dispose of beached Sargassum in local landfills, potentially wasting a valuable renewable resource. The objective of this study was to determine whether composting represents a feasible alternative to managing Sargassum inundations through measurements and comparisons to eleven guidelines. Specifically, we assessed the characteristics of the compost [physical-chemical parameters (temperature, moisture content, pH, and conductivity), nutrient ratios (C:N), elemental composition, bacteria levels, and ability to sustain plant growth] in both small- and large scale experiments. Results show that although nutrient concentration ratios were not within the standards outlined by the U.S. Composting Council (USCC), the Sargassum compost was able to sustain the growth of radishes (Raphanus sativus L., var. Champion). Trace metal concentrations in the compost product were within five regulatory guidelines evaluated, except for arsenic (As) (6.64-26.5 mg/kg), which exceeded one of the five (the Florida Soil Cleanup Target Level for residential use). Bacteria levels were consistent with regulatory guidelines for compost produced in large-scale outdoor experiments but not for the small-scale set conducted in enclosed tumblers. Overall results support that Sargassum compost can be beneficially used for fill and some farming applications.

Problems associated with vermicomposting of dog excrement in practice using Eisenia andrei

One 25-kg dog produces about 500 g of excrement per day. Excrement is a potentially hazardous material, as it may contain pathogenic microorganisms. Our samples were tested for the presence of thermotolerant coliform bacteria, Enterococcus spp., Escherichia coli and Salmonella spp., which are indicators of faecal contamination, as well as for the presence of helminths and their eggs. During the experiment, it was observed whether these microorganisms could be eliminated by vermicomposting. There were two variants of vermicomposting piles: one test pile (with continuous feeding) and one control pile (with a single feeding). The vermicomposting process was run in outdoor conditions in park for 51 weeks using Eisenia andrei earthworms. The vermicomposting of dog excrement with waste from park maintenance (1:2) can produce a good quality fertiliser. During the process of vermicomposting, there was a gradual decrease in the content of pathogenic bacteria. At the end of the vermicomposting process, there were no eggs or adult helminths. The vermicompost was very rich in microorganisms and enzymatic activity. The pH value was slightly alkaline, and the C:N ratio corresponded to value of mature vermicompost.

The earthworm microbiome is resilient to exposure to biocidal metal nanoparticles

Environmental pollution can disrupt the interactions between animals and their symbiotic bacteria, which can lead to adverse effects on the host even in the absence of direct chemical toxicity. It is therefore crucial to understand how environmental pollutants affect animal microbiomes, especially for those chemicals that are designed to target microbes. Here, we study the effects of two biocidal nanoparticles (NPs) (Ag and CuO) on the soil bacterial community and the resident gut microbiome of the earthworm Eisenia fetida over a 28-day period using metabarcoding techniques. Exposures to NPs were conducted following OECD test guidelines and effects on earthworm reproduction and juvenile biomass were additionally recorded in order to compare effects on the host to effects on microbiomes. By employing a full concentration series, we were able to link pollutants to microbiome effects in high resolution. Multivariate analysis, differential abundance analysis and species sensitivity distribution analysis showed that Ag-NPs are more toxic to soil bacteria than CuO-NPs. In contrast to the strong effects of CuO-NPs and Ag-NPs on the soil bacterial community, the earthworm gut microbiome is largely resilient to exposure to biocidal NPs. Despite this buffering effect, CuO-NPs did negatively affect the relative abundance of some earthworm symbionts, including 'Candidatus Lumbricincola'. Changes in the soil bacterial community and the earthworm microbiome occur at total copper concentrations often found or modelled to occur in agricultural fields, demonstrating that soil bacterial communities and individual taxa in the earthworm microbiome may be at risk from environmental copper exposure including in nanomaterial form.

Mutual interactions of E. andrei earthworm and pathogens during the process of vermicomposting

Vermicomposting is a process by which earthworms together with microorganisms degrade organic wastes into a humus-like material called vermicompost. This process does not include a thermophilic stage, and therefore, the possible presence of pathogens represents a potential health hazard. To elucidate the effect of earthworms in the selective reduction of pathogens, grape marc substrate was artificially inoculated with Escherichia coli, Enterococcus spp., thermotolerant coliform bacteria (TCB), and Salmonella spp., and their reduction during vermicomposting was monitored. Various defense mechanisms eliminating microorganisms in the earthworm gut were assumed to be involved in the process of pathogen reduction. Therefore, we followed the expression of three pattern recognition receptors (coelomic cytolytic factor (CCF), lipopolysaccharide-binding protein (LBP), and Toll-like receptor (v-TLR)), two antimicrobial molecules (fetidin/lysenins and lysozyme), and heat shock protein HSP70. We detected the significant decrease of some defense molecules (fetidin/lysenins and LBP) in all pathogen-inoculated substrates, and the increase of CCF and LBP in the Salmonella spp.-inoculated substrate. At the same time, the reduction of pathogens during vermicomposting was assessed. We observed the accelerated reduction of E. coli, Enterococcus spp., and TCB in pathogen-inoculated substrates with earthworms compared to that without earthworms. Moreover, the differences between the microbiome of grape marc substrate and earthworm intestines were determined by high throughput sequencing. This analysis revealed that the bacterial composition of grape marc substrate differed from the composition of the content of earthworm intestines, suggesting the elimination of specific bacterial species during food passage through the gut.

The Effects of In Vivo Exposure to Copper Oxide Nanoparticles on the Gut Microbiome, Host Immunity, and Susceptibility to a Bacterial Infection in Earthworms

Nanomaterials (NMs) can interact with the innate immunity of organisms. It remains, however, unclear whether these interactions can compromise the immune functioning of the host when faced with a disease threat. Co-exposure with pathogens is thus a powerful approach to assess the immuno-safety of NMs. In this paper, we studied the impacts of in vivo exposure to a biocidal NM on the gut microbiome, host immune responses, and susceptibility of the host to a bacterial challenge in an earthworm. Eisenia fetida were exposed to CuO-nanoparticles in soil for 28 days, after which the earthworms were challenged with the soil bacterium Bacillus subtilis. Immune responses were monitored by measuring mRNA levels of known earthworm immune genes. Effects of treatments on the gut microbiome were also assessed to link microbiome changes to immune responses. Treatments caused a shift in the earthworm gut microbiome. Despite these effects, no impacts of treatment on the expression of earthworm immune markers were recorded. The methodological approach applied in this paper provides a useful framework for improved assessment of immuno-safety of NMs. In addition, we highlight the need to investigate time as a factor in earthworm immune responses to NM exposure.

Performance and emission reduction characteristics of cerium oxide nanoparticle-water emulsion biofuel in diesel engine with modified coated piston

In the present scenario, the utilization of petroleum fuel is expanding forcefully worldwide in the vitality store and plays a highly hazardous role in the ecological system. Biofuel stands out among the most tenable keys for this issue. The lemongrass oil is used as a biofuel because of low density and viscosity when compared with diesel. The lemongrass oil is extracted by steam distillation process. In the present investigation, partially stabilized zirconium, due to its higher thermal conductivity, is selected as coating material. The top surface of the piston and the inlet and exhaust valves are coated up to the preferred thickness of 500 μm by the plasma spray technique. The lemongrass emulsion fuel is prepared in the proportion of 94% of lemongrass oil, 5% of water, and 1% of surfactant span 80. The nanoparticles of cerium oxide were used with lemongrass oil (LGO) nano-emulsion in the measurement of 30 ppm. The four-stroke diesel engine execution, ignition, and the outflow extent were contrasted in the diesel and lemongrass oil (LGO) compared with the base diesel engine. The performance characteristic curves of lemongrass-cerium oxide nano-emulsion fuel show the increase in brake thermal efficiency of 17.21% when compared with the mineral diesel fuel. The emission characteristics of lemongrass-cerium oxide nano-emulsion fuel show a drop in hydrocarbon and carbon monoxide emission by 16.21% and 15.21%, respectively, when compared with base diesel fuel and also there is a decrease in oxides of nitrogen and smoke emission by 24.1% and 6.3%, respectively, when compared to mineral diesel fuel.