Toxicological effects of aflatoxin B1 on the earthworm Eisenia fetida as determined in a contact paper test

Soil Aspergillus Species, Pathogenicity and Control Perspectives

Five Aspergillus sections have members that are established agricultural pests and producers of different metabolites, threatening global food safety. Most of these pathogenic Aspergillus species have been isolated from almost all major biomes. The soil remains the primary habitat for most of these cryptic fungi. This review explored some of the ecological attributes that have contributed immensely to the success of the pathogenicity of some members of the genus Aspergillus over time. Hence, the virulence factors of the genus Aspergillus, their ecology and others were reviewed. Furthermore, some biological control techniques were recommended. Pathogenic effects of Aspergillus species are entirely accidental; therefore, the virulence evolution prediction model in such species becomes a challenge, unlike their obligate parasite counterparts. In all, differences in virulence among organisms involved both conserved and species-specific genetic factors. If the impacts of climate change continue, new cryptic Aspergillus species will emerge and mycotoxin contamination risks will increase in all ecosystems, as these species can metabolically adjust to nutritional and biophysical challenges. As most of their gene clusters are silent, fungi continue to be a source of underexplored bioactive compounds. The World Soil Charter recognizes the relevance of soil biodiversity in supporting healthy soil functions. The question of how a balance may be struck between supporting healthy soil biodiversity and the control of toxic fungi species in the field to ensure food security is therefore pertinent. Numerous advanced strategies and biocontrol methods so far remain the most environmentally sustainable solution to the control of toxigenic fungi in the field.

Ecotoxicological Effects of Aflatoxins on Earthworms under Different Temperature and Moisture Conditions

Aflatoxin contamination remains one of the most important threats to food safety and human health. Aflatoxins are mainly found in soil, decaying plant material and food storage systems and are particularly abundant during drought stress. Regulations suggest the disposal of aflatoxin-contaminated crops by incorporation into the soil for natural degradation. However, the fate and consequences of aflatoxin in soil and on soil organisms providing essential ecological services remain unclear and could potentially pose a risk to soil health and productivity. The protection of soil biodiversity and ecosystem services are essential for the success of the declared United Nations Decade on Ecosystem Restoration. The focus of this study was to investigate the toxicological consequences of aflatoxins to earthworms’ survival, growth, reproduction and genotoxicity under different temperature and moisture conditions. Results indicated an insignificant effect of aflatoxin concentrations between 10 and 100 µg/kg on the survival, growth and reproduction but indicated a concentration-dependent increase in DNA damage at standard testing conditions. However, the interaction of the toxin with different environmental conditions, particularly low moisture, resulted in significantly reduced reproduction rates and increased DNA damage in earthworms.

Development of a sensitive indirect competitive enzyme-linked immunosorbent assay for high-throughput detection and risk assessment of aflatoxin B1 in animal-derived medicines

Animal-derived medicine is an important part of traditional Chinese medicine (TCM). Studies have shown that many animal-derived medicinal products are susceptible to contaminate of aflatoxins, nevertheless, the rapid detection for animal-derived medicine is prone to be ignored. Here we developed a sensitive indirect competitive enzyme-linked immunosorbent assay (icELISA) for rapid screening of aflatoxin B₁ (AFB₁) in ground beetle, cockroach, silkworm and earthworm. The sensitivity of the icELISA method was significantly enhanced. The IC₅₀ for the four animal-derived medicinal samples ranged from 0.092 to 0.135 ng mL^-1; the limit of detection (LOD) was 0.008-0.020 ng mL^-1. To obtain high accuracy, the extraction solution and time were evaluated. By using this method, a total of 138 samples were investigated, and the detection rates of AFB₁ in ground beetle and earthworm samples were 26.6% and 16.7%, respectively. The result was validated by liquid chromatography combined with tandem mass spectrometry, and an excellent correlation was observed between the two datasets, with a R² value of 0.999. Our results indicate that the proposed method can be used for the rapid detection of AFB₁ in animal-derived medicine. Furthermore, the quantitative risk assessment was conducted for ground beetle and earthworm based on the results, demonstrating that the intake of AFB₁ in ground beetle had a slight threat to the risk of cancer.

Cryptic speciation and blurred species boundaries of the earthworm: A challenge for soil-based toxicological risk assessments

The toxicological risk assessment of chemicals is largely based on the Organization for Economic Co-operation and Development (OECD) guidelines. These internationally approved methodologies help shape policy and political strategy of environment and human health issues. Risk assessments which pertain to soil biota 'recruit' sentinel organisms, including the earthworm Eisenia fetida. Despite E. fetida being morphologically similar to Dendrobaena veneta, they are characterized by a several-fold difference in sensitivity to xenobiotics. Worms, sold as either as pure E. fetida stocks or E. fetida/D. veneta mixed cultures, were obtained from five commercial suppliers. The species identity of 25 earthworms was determined by sequencing the cytochrome c oxidase subunit 2 (COII). We revealed that only one of 25 worms was E. fetida, the remaining worms were all identified as D. veneta. This underlines the notion that E. fetida and D. veneta are easily mis-identified. The occurrence of cryptic speciation combined with the well-documented species-specific variation in toxicological responses highlights the pressing need to accurately classify earthworms to species level prior to any toxicological research. Only this will ensure the validity and reliability of risk assessments.

Aflatoxins in the soil ecosystem: an overview of its occurrence, fate, effects and future perspectives

Aflatoxins are secondary metabolites produced by specific strains of fungi, especially Aspergillus spp. These natural toxins are mainly found in soil, decaying vegetation and food storage systems and are particularly abundant during drought stress. Aflatoxin contamination is one of the most important threats to food safety and human health due to its toxic, mutagenic and carcinogenic properties. Therefore, most research focuses on post-harvest contamination of aflatoxins in feed and food commodities but very limited information is available about aflatoxin contamination and its toxicological consequences in the soil ecosystem. Current regulations provide minimal options for the disposal of aflatoxin-contaminated crops, amongst which is the incorporation of residues into the soil for natural degradation. This form of mycotoxin loading into the soil could potentially change its physicochemical characteristics and biotic parameters. Recent studies suggest that as climate conditions change, the occurrence and geographical distribution of aflatoxins might increase, posing significant health risks to the soil ecosystem, food crop production and human health. This review will focus on studies that look at the environmental and toxicological consequences of aflatoxin contamination with the aim of clarifying the risk that aflatoxin contamination poses to soil ecosystems. Many aspects of aflatoxin occurrence, degradation and the effects of its transformation products in the soil environment are still unknown and remain an important area of research for soil health and productivity. A climatic approach, in terms of changes in soil moisture and air temperature, is important for future risk assessments of aflatoxin contamination.

Comparative analysis of vermicompost quality produced from brewers' spent grain and cow manure by the red earthworm Eisenia fetida

Brewers' spent grain (BSG) is a by-product of brewing that is usually used as low-value animal feed, although it can be better exploited in biotechnological processes, such as vermicomposting. Here, the chemical, biochemical and microbiological qualities of vermicomposts produced by the earthworm Eisenia fetida were evaluated using three substrates: BSG; cow manure (CM); BSG plus cow manure (1:1; BSG/CM). Over after 5 months of bioconversion by earthworms and microorganisms (thereafter vermicomposting), BSG and BSG/CM showed reduced total organic carbon, and increased total nitrogen and total humic substances like (HSl), suggesting enhanced mineralisation and stabilisation. Suitability of BSG as substrate for earthworms was confirmed by the earthworm fatty acid profile, characterised by prevalence of C:17, C18:1, C18:2 and C18:3 fatty acids. Higher fungi and yeast abundance in BSG vermicompost was accompanied by higher dehydrogenase activity. E. coli, Salmonella spp. and Ochratoxin A levels were below the legal limits.