Concept: Aspergillus parasiticus
Aspergillus parasiticus produces the minor aflatoxins M(1) (AFM(1)), M(2) (AFM(2)), GM(1) (AFGM(1)), and GM(2) (AFGM(2)), as well as the major aflatoxins B(1) (AFB(1)), B(2) (AFB(2)), G(1) (AFG(1)), and G(2) (AFG(2)). Feeding of A. parasiticus with aspertoxin (12c-hydroxyOMST) caused AFM(1) and AFGM(1), and cell-free experiments using the microsomal fraction of A. parasiticus and aspertoxin caused production of AFM(1), indicating that aspertoxin is a precursor of AFM(1) and AFGM(1). Feeding of the same fungus with O-methylsterigmatocystin (OMST) caused AFM(1) and AFGM(1) together with AFB(1) and AFG(1); feeding with dihydroOMST (DHOMST) caused AFM(2) and AFGM(2) together with AFB(2) and AFG(2). Incubation of either the microsomal fraction or OrdA enzyme-expressing yeast with OMST caused production of aspertoxin together with AFM(1) and AFB(1). These results demonstrated that the OrdA enzyme catalyzes both 12c-hydroxylation reaction from OMST to aspertoxin and the successive reaction from aspertoxin to AFM(1). In contrast, feeding of the fungus with AFB(1) did not produce any AFM(1), demonstrating that M-/GM-aflatoxins are not produced from B-/G-aflatoxins. Furthermore, AFM(1) together with AFB(1) and AFG(1) was also produced from 11-hydroxyOMST (HOMST) in feeding experiment of A. parasiticus, whereas no aflatoxins were produced when used the ordA deletion mutant. These results demonstrated that OrdA enzyme can also catalyze 12c-hydroxylation of HOMST to produce 11-hydroxyaspertoxin, which serves as a precursor for the production of AFM(1) and AFGM(1). The same pathway may work for the production of AFM(2) and AFGM(2) from DHOMST and dihydroHOMST through the formation of dihydroaspertoxin and dihydro-11-hydroxyaspertoxin, respectively.
- International journal of environmental research and public health
- Published about 3 years ago
Aflatoxins are produced by the fungi Aspergillus flavus and Aspergillus parasiticus and are common food contaminants in tropical developing countries. Extensive aflatoxin consumption has been shown to be highly associated with liver disease. A case-control study was conducted to determine the association between aflatoxin and liver disease in Kumasi, Ghana. A questionnaire was administered to examine socio-demographic characteristics and food storage and consumption practices, and urine samples were collected to measure levels of the aflatoxin metabolite (AFM₁). Two hundred and seventy-six people participated in the study; 38 had liver disease (cases), 136 had neither hepatitis B/C nor liver disease (negative controls), and 102 were hepatitis B/C positive without liver cancer (positive controls). A much higher percent of participants in each group was male (76% of cases, 88% of negative controls and 65% of positive controls). Multivariate analysis showed that age was a significant predictor for being a case when cases were compared to negative controls. The odds of being a case was 70% less for participants aged 25-34 years (odds ratios (OR) 0.30; 95% confidence interval (CI) 0.10-0.88) compared to those ≥45 years. For cases; Akans were seven times more likely to have AFM₁ levels below the median when compared to other ethnic groups (OR 7; CI 1.41-34.68). When cases were compared to positive controls, they were 2.29 times more likely to report awareness of aflatoxin contamination of groundnuts (95% CI 1.06-4.91). Cases were also two times more likely to report awareness of aflatoxin contamination of maize than all controls combined (95% CI 1.02-4.11). However, most cases reported that aflatoxin contamination does not cause sickness in humans. This shows that there is awareness of aflatoxin contamination without proper understanding of the serious potential adverse health impacts among these study participants. These findings indicate that educational interventions that stress the harmful health effects of aflatoxin in food, with an emphasis on the higher risk for males, are urgently needed. The reasons for lower aflatoxin levels among Akans need to be determined, and the findings used to design interventions that benefit other ethnic groups in the society.
Aflatoxin B1 (AFB₁) is produced by the Aspergillus flavus and Aspergillus parasiticus group of fungi which is most hepatotoxic and hepatocarcinogenic and occurs as a contaminant in a variety of foods. AFB₁ is mutagenic, teratogenic, and causes immunosuppression in animals and is mostly found in peanuts, corn, and food grains. Therefore, novel methodologies of sensitive and expedient strategy are often required to detect mycotoxins at the lowest level. Herein, we report an electrochemical impedance sensor that selectively detects AFB₁ at the lowest level by utilizing polyaniline nanofibers (PANI) coated with gold (Au) nanoparticles composite based indium tin oxide (ITO) disk electrodes. The Au-PANI nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and electrochemical impedance spectroscopy (EIS). The composite electrode exhibited a 14-fold decrement in |Z|1Hz in comparison with the bare electrode. The Au-PANI acted as an effective sensing platform having high surface area, electrochemical conductivity, and biocompatibility which enabled greater loading deposits of capture antibodies. As a result, the presence of AFB₁ was screened with high sensitivity and stability by monitoring the changes in impedance magnitude (|Z|) in the presence of a standard iron probe which was target specific and proportional to logarithmic AFB₁ concentrations (CAFB₁). The sensor exhibits a linear range 0.1 to 100 ng/mL with a detection limit (3) of 0.05 ng/mL and possesses good reproducibility and high selectivity against another fungal mycotoxin, Ochratoxin A (OTA). With regard to the practicability, the proposed sensor was successfully applied to spiked corn samples and proved excellent potential for AFB₁ detection and development of point-of-care (POC) disease sensing applications.
Aspergillus flavus is an opportunistic pathogen and may produce aflatoxins in maize, one of the most important crops in Argentina. A promising strategy to reduce aflatoxin accumulation is the biological control based on competitive exclusion. In order to select potential biocontrol agents among isolates from the maize growing region in Argentina, a total of 512 A. flavus strains were isolated from maize kernels and soil samples. Thirty-six per cent of the isolates from maize kernels did not produce detectable levels of aflatoxins, while 73% of the isolates from soil were characterized as non-aflatoxin producers. Forty percent and 49% of the isolates from maize kernels and soil samples, respectively, were not producers of cyclopiazonic acid (CPA). Sclerotia morphology was evaluated using Czapek Dox media. Eighty-six per cent of the isolates from maize kernels and 85% of the isolates from soil samples were L sclerotia morphotype (average diameter > 400 μm). The remaining isolates did not produce sclerotia. All isolates had MAT 1-1 idiomorph. The competitive ability of 9 non aflatoxigenic strains, 4 CPA(+) and 5 CPA(-), was evaluated in co-inoculations of maize kernels with an aflatoxigenic strain. All evaluated strains significantly (p < 0.05) reduced aflatoxin contamination in maize kernels. The aflatoxin B1 (AFB1) reduction ranged from 6 to 60%. The strain A. flavus ARG5/30 isolated from maize kernels would be a good candidate as a potential biocontrol agent to be used in maize, since it was characterized as neither aflatoxin nor CPA producer, morphotype L, MAT 1-1 idiomorph, and reduced AFB1 content in maize kernels by 59%. This study showed the competitive ability of potential aflatoxin biocontrol agents to be evaluated under field trials in a maize agro-ecosystem in Argentina.
Herbs derived from roots, leaves, flowers, or fruits of plants are unavoidably contaminated with fungi and mycotoxins during growth, harvest, and storage, thereby posing a health threat to humans. Especially, root herbs (RHs) are more easily contaminated with fungi and mycotoxins because the roots are in direct contact with the soil. Here, we investigated the occurrence of fungi, aflatoxins (AFs), and ochratoxin A (OTA) in eight RHs that are used as medicines, beverages, dietary supplements, and functional foods in China and other countries. Morphological observation and MultiGeneBlast (β-tubulin and calmodulin) were used to identify the potentially toxigenic fungi. Of the 48 samples tested, all were contaminated by fungi, and 1,844 isolates belonging to 25 genera were detected. The genera Aspergillus and Penicillium, which contain potentially toxigenic fungal species, represented a frequency of 10 and 25%, respectively. Thirty-three isolates of Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger, and Penicillium polonicum were arbitrarily selected for analysis of their toxigenic potential. Five of 13 isolates of A. flavus and 1 isolate of A. parasiticus produced AFs, whereas OTA production was not detected for any of the isolates of A. niger and P. polonicum. The occurrence of AFs and OTA in the 48 samples of eight RHs was tested by ultraperformance liquid chromatography-tandem mass spectrometry; 37.50% of samples from six RHs were contaminated with AFs and 16.67% of samples from four RHs were contaminated with OTA. Seven (14.58%) and four (8.33%) samples of ginseng, polygala, and liquorice exceeded the permissible limits of aflatoxin B1and AFs, respectively. Because ginseng, polygala, and liquorice are widely used as herbs, dietary supplements, and functional foods, the high frequency of AF contamination of these herbs indicated by our current study warrant attention to raise public awareness.
Brazil produce approximately 63 million tons of corn kernels annually, which is commonly contaminated with fungi and mycotoxins. The objective of this study was to evaluate the efficacy of gaseous allyl isothiocyanate (AITC) to inhibit the growth of Aspergillus parasiticus and Fusarium verticillioides, and mycotoxin production (aflatoxins B1 , B2 , G1 and G2 , fumonisins B1 and B2 ) in corn during 180 d of storage.
Aflatoxin B1(AFB1) is a naturally occurring secondary metabolites of Aspergillus flavus and Aspergillus parasiticus, and is the most toxic form of aflatoxins. Selenium (Se) with antioxidant and detoxification functions is one of the essential trace elements for human beings and animals. This study aims to evaluate the protective effects of Se on AFB1-induced tissue damage and cell cycle arrest in bursa of Fabricius (BF) of chickens. The results showed that a dietary supplement of 0.4 mg·kg-1Se alleviated the histological lesions induced by AFB1, as demonstrated by decreasing vacuoles and nuclear debris, and relieving oxidative stress. Furthermore, flow cytometry studies showed that a Se supplement protected AFB1-induced G2M phase arrest at 7 days and G0G1phase arrest at 14 and 21 days. Moreover, the mRNA expression results of ATM, Chk2, p53, p21, cdc25, PCNA, cyclin D1, cyclin E1, cyclin B3, CDK6, CDK2, and cdc2 indicated that Se supplement could restore these parameters to be close to those in the control group. It is concluded that a dietary supplement of 0.4 mg kg-1Se could diminish AFB1-induced immune toxicity in chicken’s BF by alleviating oxidative damage and cell cycle arrest through an ATM-Chk2-cdc25 route and the ATM-Chk2-p21 pathway.
- Food additives & contaminants. Part B, Surveillance
- Published about 1 year ago
The presence of Aspergillus section Flavi and aflatoxin (AF) contamination was investigated in 112 samples of peanuts, almonds and dried figs collected in Algeria. The occurrence of aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) in different commodities has been determined with a sensitive method based on high performance liquid chromatography (HPLC) coupled with fluorescence detection with post-column photochemical derivatization. Analytical results indicated that 28 samples of peanuts, 16 samples of almonds and 26 samples of dried figs contained detectable levels of AFS. A total of 69 samples (61.6%) were contaminated with AFB1 ranging from the limit of quantification to 174 μg kg-1. AFB2 was found in 12 samples (10.7%) and varied from 0.18 to 193 μg kg-1. Seven samples revealed AF concentrations lower than the limit of quantification. Eleven peanut and fourteen dried fig samples exceeded the European maximum limits for AFB1.
An extensive sampling of Aspergillus section Flavi considered to be the main agent responsible for aflatoxin contamination, was carried out in the field and along the processing phases of chestnut flour production in 2015. Fifty-eight isolates were characterized by means of biological, molecular and chemical assays. The highest incidence of Aspergillus section Flavi was found in the field. The identification of the isolates was based on β-tubulin and calmodulin gene sequences. A. flavus was found to be the dominant species, and this was followed by A. oryzae var effusus, A. tamarii, A. parasiticus and A. toxicarius. Nineteen percent of the strains produced aflatoxins in vitro and forty percent in vivo. The pathogenicity assay on chestnut showed 56 virulent strains out of 58. The molecular, morphological, chemical and biological analyses of A. flavus strains showed an intraspecific variability. These results confirm that a polyphasic approach is necessary to discriminate the species inside the Aspergillus section Flavi. The present research is the first monitoring and characterization of aflatoxigenic fungi from fresh chestnut and the chestnut flour process, and it highlights the risk of a potential contamination along the whole chestnut production chain.
Selected plant essential oils and their main active components, a promising approach to inhibit aflatoxigenic fungi and aflatoxin production in food
- Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment
- Published over 1 year ago
Recent research has showed that Aspergillus flavus and Aspergillus parasiticus are aflatoxigenic species that can become very competitive in the framework of climate change. Aflatoxins show carcinogenic, mutagenic, immunotoxic and teratogenic effects on human and animals. Effective and sustainable measures to inhibit these species and aflatoxins in food are required. Origanum vulgare and Cinnamomum zeylanicum essential oils (EOs) and their major active constituents, carvacrol and cinnamaldehyde, respectively, were assayed for inhibiting these species and aflatoxin production in maize extract medium under different environmental conditions. Doses of 10-1000 mg l-1 were assayed and the effective doses for 50 (ED50) and 90% (ED90) growth inhibition were determined. The ED50 of cinnamaldehyde, carvacrol, oregano EO, and cinnamon EO against A. flavus were in the ranges 49-52.6, 98-145, 152-505, 295-560 mg l-1 and against A. parasiticus in the ranges 46-55.5, 101-175, 260-425 and 490-675 mg l-1, respectively, depending on environmental conditions. In A. flavus treatments ED90 were in the ranges 89.7-90.5, 770-860 and 820->1000 mg l-1 for cinnamaldehyde, carvacrol and cinnamon EO, and in A. parasiticus treatments in the ranges 89-91, 855->1000 and 900->1000 mg l-1, respectively. ED90 values for oregano EO against both species were >1000 mg l-1. Growth rates of both species were higher at 37 than at 25°C and at 0.99 than at 0.96 aw. Aflatoxin production was higher at 25 than at 37°C. Stimulation of aflatoxin production was observed at low doses except for cinnamaldehyde treatments. The effectiveness of EOs and their main constituents to inhibit fungal growth and aflatoxin production in contact assays was lower than in vapour phase assays using bioactive EVOH-EO films previously reported.