Aflatoxin contamination of dried red chilies: Contrasts between the United States and Nigeria,two markets differing in regulation enforcement

Dried red chilies are among the world’s most consumed spices. From farm to fork, chilies go through cropping, harvest, drying, processing and storage. Chilies are susceptible to infection by aflatoxin producing fungi and subsequent contamination by aflatoxins at every stage. Aflatoxins are highly regulated, hepatotoxic carcinogens produced by fungi in Aspergillus section Flavi. The current study examined prevalence of aflatoxin B₁ (AFB₁) in chilies from markets across the United States (US) and Nigeria, and determined predisposition of chilies to aflatoxins post-harvest. Aflatoxin B₁ was detected in 64% chilies from US markets (n = 169), and 93% of Nigerian chilies (n = 55) with a commercial lateral flow assay (Limit of Detection = 2 μg/kg). Two percent of US samples exceeded the aflatoxin regulatory limit of 20 μg/kg, while the highest concentration detected was 94.9 μg/kg. Aspergillus spp. could be recovered only from 40% of samples from the US, and aflatoxin levels did not correlate with quantities of Aspergillus section Flavi (Colony Forming Units g⁻¹), suggesting fungi associated with chilies in US markets were killed during processing. Both average AFB₁ concentrations and fungal quantities were significantly higher (p < 0.01) in Nigerian chilies. The most contaminated sample contained 156 μg/kg AFB₁. Aflatoxin concentrations in Nigerian chilies increased as an exponential function of the quantities of Aspergillus section Flavi (r² = 0.76). Results indicate that high rates of chili consumption may be associated with unacceptable aflatoxin exposure.     

Aflatoxin B1 production by Aspergillus parasiticus and strains of Aspergillus section Nigri in currants of Greek origin

Aflatoxin B₁ (AFB₁) mostly produced by Aspergillus flavus and Aspergillus parasiticus, is an extremely toxic and carcinogenic metabolite. Currants are used in the Mediterranean diet as a food with antioxidant properties. Four strains of Aspergillus section Nigri have been isolated from currants originated from Crete and Corinth. In this study AFB₁ production by A. parasiticus and the four strains of Aspergillus section Nigri in Cretan and Corinthian currants (Vitis vinifera L.) is investigated. AFB₁ determination was performed by HPLC–FID. Results revealed that the four strains Aspergillus section Nigri, as well as the aflatoxigenic strain A. parasiticus produced AFB₁ (0.0052–1.31 μg AFB₁ 15 g⁻¹, corresponding to 0.0003–0.087 μg AFB₁ g⁻¹) in both type of currants (Cretan and Corinthian) on the 12th day of observation. Moreover, AFB₁ production, by A. parasiticus in the synthetic Yeast Extract Sucrose (YES) medium was also studied. The ability of AFB₁ production has been affected by the special characteristics of each isolate and the currants substrate.     

Inactivation of aflatoxigenic fungi and the reduction of aflatoxin B1 in vitro and in situ using gamma irradiation

Detailed investigation on the effect of gamma (γ) irradiation on germination, sporulation, and growth of aflatoxigenic moulds (Aspergillus parasiticus 2999, Aspergillus flavus 305, and Aspergillus niger 388), as well as on the reduction of aflatoxin B₁ (AFB₁) level in artificially and naturally contaminated maize/feed samples was performed. The results of in vitro and in situ experiments with aflatoxigenic moulds demonstrated that 5 kGy-γ irradiation manages to prevent sporulation, germination and growth of the tested moulds both when in form of a pure and when in form of a mixed culture. In the feed samples artificially contaminated with AFB₁ (50 μg kg⁻¹) 5 kGy-γ irradiation reduced AFB₁ level by around 60%, while 10 kGy-dose reduce it for around 85%. Similarly, in feed samples spiked with AFB₁ in the concentrations of 100 μg kg⁻¹ 5 kGy-dose reduced the AFB₁ level by approximately 70%, while the dose of 10 kGy reduced it by approximately 90%. The experiments on naturally contaminated maize samples (n = 30) confirmed these observations; following a 5 kGy-irradiation, the overall mean AFB₁ reduction equalled to 69.8%, while the irradiation with a 10 kGy-dose achieved the overall mean toxin reduction of 94.5%. The obtained results indicate that γ irradiation can be used to prevent the growth of aflatoxigenic moulds and to reduce the AFB₁ levels in various goods intended for animal and human consumption, thus minimizing the animal and human exposure to this carcinogenic mycotoxin.     

Evaluation of latex agglutination inhibition reaction test for rapid detection of aflatoxin B1

Aflatoxin B₁ (AFB₁), a mycotoxin mainly produced by some Aspergillus species, has been found in a wide range of agricultural products. To avoid the risk of AFB₁ consumption, many agricultural commodities, foods and feeds should be analyzed and a rapid and non-instrumental method for the detection of AFB₁ is needed. In this study, a rapid, inexpensive and user-friendly latex agglutination inhibition reaction test (LAIRT) for on site testing of AFB₁ had been established. At first, carboxylated polystyrene latex particles (CPLP) were prepared by soap-free polymerization and sensitized with aflatoxin B₁ oxime-BSA (AFB₁O-BSA) for the detection of AFB₁. In LAIRT, the agglutination reaction with AFB₁O-BSA-sensitized CPLP and anti-AFB₁ antiserum mixture was inhibited by 5 ng/mL AFB₁ and the analysis time for 6 samples on one glass slide was less than 10 min. Subsequently, 10 rice and peanut samples were analyzed by LAIRT and ELISA, and the results showed that 1 rice sample and 2 peanut samples were positive and in agreement with those of ELISA. However, the results could be obtained more rapidly by LAIRT than ELISA. This easy and rapid LAIRT might be useful for screening AFB₁ of agricultural commodities, foods and feeds in the field.     

Effect of Hibiscus sabdariffa extract and Nigella sativa oil on the growth and aflatoxin B1 production of Aspergillus flavus and Aspergillus parasiticus strains

This study was undertaken to evaluate the inhibitory effect of Hibiscus sabdariffa calyx extract at concentrations of 5, 7.5, 10 and 12.5 g/100 ml and Nigella sativa oil at concentrations of 1, 2 and 3 ml/100 ml on the growth and aflatoxin B₁ production by Aspergillus parasiticus (CBS 921.7) and Aspergillus flavus (SQU 21) strains. The inhibition of aflatoxin B₁ production by the different concentrations of H. sabdariffa calyx ranged between 91.5-97.9% and 87.1-93.3% for A. flavus and A. parasiticus strains, respectively, whereas the inhibition by different concentrations of N. sativa oil ranged between 47.9 and 58.3% for A. flavus and 32-48% for A. parasiticus strains. The different concentrations of H. sabdariffa calyx and N. sativa oil had no significant effect on the growth of either Aspergillus species. Neither H. sabdariffa calyx nor N. sativa oil detoxified pure aqueous aflatoxin. Our results suggest that H. sabdariffa calyx and N. sativa oil extracted from seeds had metabolic effects on aflatoxin biosynthesis pathway of both Aspergillus species and can be used as an effective biocontrol and non-toxic biopreservatives in food industry against aflatoxin contamination.     

Effect of water activity and temperature on the growth of Aspergillus flavus,the expression of aflatoxin biosynthetic genes and aflatoxin production in shelled peanuts

The contamination of peanuts with Aspergillus flavus and subsequent aflatoxins is considered to be one of the most serious safety problems in the world. Water activity (a_w) and temperature are limiting factors for fungal growth and aflatoxins production during storage. To optimize the practical storage parameter, the effect of a_w (0.85–0.99) and temperature (15–42 °C) on fungal growth, aflatoxin production and the expression of aflatoxin biosynthetic and regulatory genes in shelled peanuts was investigated. A. flavus grew at a lower rate when temperature ≤20 °C or a_w ≤ 0.85. For the growth of A. flavus in shelled peanuts, the optimum conditions were a_w was 0.98, and the optimum temperature was 37 °C. The maximum amount of AFB₁ in peanuts was obtained at 28 °C and a_w 0.96. Real-time analysis showed that 16 of 25 genes had highest expression levels at 28 °C under a_w 0.92, while 9 genes had highest expression levels at 37 °C under a_w 0.92. Compared with 37 °C, all aflatoxin biosynthetic pathway genes were down-regulated at 42 °C. All the pathway genes and laeA were up-expressed at a_w of 0.96 under 28 °C, compared to a_w 0.99. Furthermore, there was a good positive correlation between the ratio of aflS/aflR and AFB₁ production. The expression of laeA was also positively correlated with AFB₁ production while the expression of brlA was correlated with the A. flavus growth. The results of this study suggest that AFB₁ production in peanut kernels can occur over a wider range of a_w × temperatures levels compared to formula media and peanut media. Previous studies have showed that AFB₁ could not be produced on formula media at 37 °C without the expression of most aflatoxin structural genes. But, in the un-autoclaved shelled peanuts, high concentration of AFB₁ was produced at 37 °C with up-regulation of some aflatoxin biosynthetic genes. From a food safety point of view, the results can be used to optimize certain food technological processes and develop prevention strategies to control such carcinogenic natural metabolites in grains (such as peanuts, maize and rice) and derived products.     

Aflatoxin-producing Aspergillus spp. and aflatoxin levels in stored cassava chips as affected by processing practices

Cassava chips (cassava balls, and cassava pellets) are derived cassava products traditionally produced by farmers in sub-Saharan Africa following fermentation, and drying of fresh roots of cassava, and are widely consumed in Cameroon. Once produced, this food commodity can be stored for more than two months and contaminated by a wide array of harmful microbes. In order to assess persistence of toxigenic fungi in cassava chips, aflatoxin-producing fungi (Aspergillus flavus, Aspergillus nomius, and Aspergillus parasiticus) and aflatoxins were contrasted at regular intervals in home-stored cassava chips collected in two locations of southern Cameroon throughout a two-month monitoring period. Three hundred and forty-six isolates of aflatoxin-producing fungi were found to be associated with all samples. A. flavus contaminated more samples in both types of chips (267 isolates in 53 samples), followed by A. nomius (58 isolates in 15 samples), whereas A. parasiticus was rarest. A direct competitive Enzyme-linked immunosorbent assay (ELISA)-based method was implemented to quantify the content in aflatoxins. Eighteen of the samples contained some aflatoxins at detectable levels whereas 54 did not. The levels of aflatoxin ranged between 5.2 and 14.5 ppb. The distribution of aflatoxin in positive samples depended on 8 parameters including pH, moisture content, storage duration, types of chips, level of contamination by aflatoxin-producing fungi, processing practices and storage facilities. From analysis of variance results, only pH (p < 0.01), duration of storage (p < 0.01), population of aflatoxin-producing species (0.0001) and the chip type (p < 0.05) were significantly related to aflatoxin in positive samples. A stepwise regression analysis (forward selection procedure) indicated that aflatoxin levels were significantly (p < 0.01) correlated with processing practices, storage facilities, and storage duration of the chips.     

Isolation and characterization of a Bacillus subtilis strain with aflatoxin B1 biodegradation capability

Aflatoxins are type of mycotoxins mainly produced by Aspergillus flavus and a common contaminant of food and grain, posing a serious economic and health problem worldwide. In order to find efficient bacteria to remove or detoxify these mycotoxins, a bacterial strain capable of degrading aflatoxin B₁ (AFB₁) was isolated from soil samples using a culture medium containing coumarin as the sole carbon source. Based on 16S rRNA gene sequence analysis, this isolate was identified as Bacillus subtilis JSW-1; its further characterization showed that it could inhibit the growth of A. flavus with an inhibition ratio of 58.3% and could degrade AFB₁ by 67.2% after incubation at 30 °C for 72 h. The aflatoxin B₁-degrading activity of isolate JSW-1 was predominantly attributed to the cell-free supernatant and this activity was found to be heat stable but sensitive to proteinase K treatment, indicating that the extracellular proteins or enzymes are responsible for the AFB₁ degradation. In addition, no degradation products of AFB₁ could be detected by liquid chromatography-mass spectrometry (LC-MS) analysis, indicating that the parent AFB₁ might be biotransformed to compounds with chemical properties different from that of AFB₁.     

Development of an aptasensor for the fast detection of Versicolorin A

Aflatoxins (AFs) are secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus. The molds may contribute to pre-harvest aflatoxin contamination of susceptible crops. For the customer and food producer, a predictive model for aflatoxin detection is very desirable. Versicolorin A (VerA), which is the first precursor in the pathway of aflatoxin B₁ (AFB₁) biosynthesis, shares similar toxic group with the furofuran structure in aflatoxin B₁. VerA exhibits a much lower teratogenic toxicity than AFB₁ and may be used as a predictive indicator for aflatoxin B₁ contamination of storage crops. Therefore, the development of a fast detection method for VerA is important. One of the randomly computer-generated aptamers of VerA was confirmed by isothermal titration calorimetry with K_d = 9.26 × 10⁻⁶ mol l⁻¹. In addition, a simple and sensitive label-free aptasensor was developed for the electrochemical detection of VerA. According to the results from differential pulse voltammetry (DPV), a linear relationship existed between the log conc. of VerA (ranged from 0.01 to 100 ng ml⁻¹) and the current (△I_p) with a limit of detection (LOD) of 10 pg ml⁻¹. The resulting aptasensor exhibited good reproducibility for detecting VerA and stability after storage for 15 days at 4 °C with acceptable anti-interference against ZEN, OTA, DON, and FB₁. When used in corn samples, the recoveries of VerA were determined to be in the range of 81.3%–104.4 %. Although with some intercross, result suggests that the obtained aptamer for VerA is potentially used as a sorbent for the preparation of solid-phase-extraction procedure to clean up food samples in conjunction with high-performance liquid chromatography analysis.     

A survey of mycotoxins in random street-vended snacks from Lagos,Nigeria, using QuEChERS-HPLC-MS/MS

A survey in African snacks was carried out in order to evaluate the intake of 23 mycotoxins. The African snack samples were purchased from street vendors within Lagos metropolis (Nigeria) and evaluated for the presence of 23 mycotoxins using a modified QuEChERS procedure coupled with liquid chromatography-triple quadrupole linear ion trap mass spectrometer. The snacks included akara, baked coconut, coconut candy, donkwa, groundnut cake (kulikuli), lafun, milk curd (wara), fresh and dried tiger-nuts, and yam flour. Only three mycotoxins were detected in 23.8% of the studied snacks, and at concentrations ranging from 6 to 54 μg kg⁻¹. The concentrations of aflatoxin B₁ (AFB₁) and AFB₂ reached 23 μg kg⁻¹ and 3 μg kg⁻¹, respectively. Moreover a sample of baked coconut contained α-zearalenol (α-ZOL), which was up to 54 μg kg⁻¹ in coconut candy. As considers prevalence, aflatoxins and α-ZOL were not detected in lafun and groundnut-based snacks (donkwa and kulikuli), whereas each of the three mycotoxins contaminated 12.5% (1/8) of the coconut-based samples. This is the first report of α-ZOL in cassava and coconut, and their products. AFB₁ and total aflatoxins (TAFs) concentrations exceeded the maximum allowable limit recommended by National Agency for Food and Drug Administration and Control Nigeria (NAFDAC) in one sample of baked coconut (AFB₁ = 23 μg kg⁻¹ and TAFs = 26 μg kg⁻¹) and donkwa (AFB₁ = 19 μg kg⁻¹ and TAFs = 21 μg kg⁻¹).     

Annual and regional variations of aflatoxin B1 levels seen in grains and feed coming from Croatian dairy farms over a 5-year period

The aim of the study was to investigate annual and regional differences in the level of aflatoxin B₁ (AFB₁) in grains and dairy cattle feed. Maize (n = 972), wheat (n = 201), barley (n = 147), oat (n = 136), grain mixtures (n = 168), and dairy cattle feed (n = 325) were sampled from 2009 to 2013 on different farms and in different farm factories situated in four Croatian regions. The samples were analysed for AFB₁ using the validated ELISA immunoassay. AFB₁ was determined in 16.4% of all investigated samples, among which maize was proven to be the most contaminated, with 21.7% of the samples recovered during 2013 harbouring AFB₁ in concentrations over the permissible ones. Levels higher than permitted were observed in 17.9% and 12.3% of grain mixtures and dairy cattle feed, respectively, whereas concentrations of AFB₁ determined in other crops throughout the investigated period met the stipulated requirements. The results revealed the AFB₁ occurrence to be significantly (p < 0.05) dependent on the cultivation region, with the highest levels generally found in maize harvested in 2013 and consequently in grain mixtures and cattle feed that can most likely be associated with climatic conditions as the most critical factor for mould formation, and thus also AFB₁ production.     

Occurrence of toxigenic fungi and ochratoxin A in Ethiopian coffee for local consumption

Information on the presence of ochratoxin A (OTA) in local Ethiopian coffee is scarce. Therefore, the objective of this study was to type the fungal and mycotoxin contamination levels in Ethiopian coffee consumed by the local community. Coffee samples were collected from six major coffee growing districts in Jimma zone of Oromiya regional state in Ethiopia. Total fungal incidence mounted up to 87% and Aspergillus (79%), Fusarium (8%) and Penicillium (5%) were the predominant toxigenic genera. OTA producing species A. westerdijkiae, Aspergillus ochraceus, and Aspergillus steynii were identified for the first time in Ethiopia and were shown to be the predominant species while aflatoxin (AF) producing Aspergillus species were scarce. Using an in vitro approach, the OTA production potential was assessed under standardized conditions. Based on this experiment, it was concluded that Aspergillus westerdijkiae isolates were clearly the most potent producers of OTA. The median OTA level in the locally sold Ethiopian coffee was 1.53 μg/kg. Notwithstanding this low median value, significant differences in fungal and toxin incidences were observed between the different coffee processing types, coffee sample types, and storage characteristics.     

Inhibition of non-toxigenic Aspergillus niger FS10 isolated from Chinese fermented soybean on growth and aflatoxin B1 production by Aspergillus flavus

A non-toxigenic strain FS10 was isolated from Chinese fermented soybean to control AFB₁ contamination and conformed as Aspergillus niger by 18S rDNA. To elucidate the biocontrol mechanism, the ability of culture filtrate of strain FS10 against growth and AFB₁ production by toxigenic Aspergillus flavus was evaluated in vitro. Meanwhile, the influence of filtrate on spore morphology of A. flavus was analyzed by optical microscope and atomic force microscope (AFM). Results demonstrated that the culture filtrate of FS10 significantly suppressed A. flavus growth, sporulation and AFB₁ biosynthesis. After 9 days, the inhibition of mycelia growth, sporulation and AFB₁ production reached to 37.7%, 100% and 94.5%, respectively. In addition, optical microscopy and AFM showed that the culture filtrate serious damaged spore morphology, accompanying with spore analysis and cell wall collapse, resulted in inhibition of spore germination. The degradation activity of FS10 culture filtrate on AFB₁ was also estimated. When AFB₁ was incubated with the culture filtrate, 85.8% of AFB₁ could be degraded after 5 days. It is concluded that the culture filtrate of strain FS10 has pleiotropic effects on control AFB₁ contamination. As a safe, effective and economic biological agent, the filtrate could be applied in fermented food to prevent toxigenic Aspergillus spp. and AFB₁ contamination.     

Natural occurrence of aflatoxin B1, ochratoxin A and citrinin in Croatian fermented meat products

When domestic animals are exposed to mycotoxins, significant amounts of the latter shall be carried over into animal products such as milk, eggs and meat. This study was carried out in order to determine the possible presence of aflatoxin B₁ (AFB₁), ochratoxin A (OTA) and citrinin (CIT) in game sausages (n = 15), semi-dry sausages (n = 25) and fermented dry-meat products (n = 50), randomly taken from individual producers and the Croatian market. AFB₁ and OTA were quantified using ELISA, while CIT was quantified using HPLC-fluorescence detector. Out of 90 samples, the fungi most frequently isolated from dry-cured meat products were of Penicillium species, while Aspergillus was isolated from only one sample. As much as 68.88% of the samples were positive for mycotoxins. Finally, the analysis of different types of meat products resulted in OTA identification in 64.44%, CIT identification in 4.44% and AFB₁ identification in 10% of the samples. The maximum OTA concentrations established in the commercial sausage samples equalled to 7.83 μg/kg, while that of AFB₁ amounted to 3.0 μg/kg. Generally, although OTA was detected in all three types of products in different percentage shares, mutual differences were not statistically significant (P > 0.05).     

Mid-infrared spectroscopy for discrimination and classification of Aspergillus spp. contamination in peanuts

In this study, Aspergillus spp., common colonists in peanut, were characterized, classified and quantified using FTIR coupled with ATR accessory. FTIR-ATR spectral data of infected peanut samples were preprocessed (mean-centering, smoothing the 1st derivative), and used for the PLS regression analysis for quantitative results. Very high R² values (96.20–99.98%) together with low error of RMSEC values (0.014–0.153 Log CFU/g of peanut) were obtained. Even, the spectrum of peanut matrix was dominant at early stages of invasion (≤2.5 Log CFU/g peanut), resulting in section separation (Nigri from Flavi) and at higher population (>4 Log CFU/g, species level separation (Aspergillus alliaceus, Aspergillus caelatus, Aspergillus flavus, Aspergillus parasiticus, and Aspergillus tamari) was observed. The accuracy of correct classification increased proportionally with fungal invasion level and 100% correct classification was reached when the cell level was Log CFU/g = 4.5–5. Samples with similar secondary metabolites (toxin producers) grouped close-by in PC score diagrams for all levels of fungal growth. Results highlight the possible implementation of FTIR-ATR model to detect infected peanuts even at early stages of invasion; besides, to prove the potential separation capability in terms of species and their secondary metabolites.     

Fungal and aflatoxin contamination of marketed spices

Fourteen spice samples were collected from local markets in Doha, Qatar, during 2012, and were surveyed for the presence of potentially harmful mycoflora and for contamination with aflatoxins B₁, B₂, G₁, and G₂ by high-performance liquid chromatography (HPLC). Among the tested spice samples, chili powder showed the highest presence of fungal propagules, while ginger, curry and garlic samples did not present any fungal contamination. A total of 120 isolates, mostly belonging to Aspergillus and Penicillium genera, were collected and 33 representative species were identified by amplification and sequencing of the internal transcribed spacer (ITS) region. Aspergillus flavus, Aspergillus nomius and Aspergillus niger were the most dominant. Thirty-seven Aspergillus strains were screened for their potential to produce aflatoxins using biochemical and molecular tools: only 9 A. flavus strains showed both fluorescence and amplification with all the three primers targeting aflP, aflM and aflR genes. Aflatoxins were detected in five spices (black pepper, chili, tandoori masala. turmeric and garam masala), and with the exception of garam masala, the tested samples of turmeric, black pepper, tandoori masala and chili powder exceeded B₁ and/or total aflatoxin maximum levels. Our results demonstrate the potential for mycotoxin biosynthesis by fungi contaminating imported spice products.     

Effectiveness of pulsed light treatment for degradation and detoxification of aflatoxin B1 and B2 in rough rice and rice bran

Aflatoxins primarily accumulate in the hull and bran layers of rough rice making these by-products of rice milling unsuitable for animal feed or human consumption. Contaminated rough rice is also a potential source of aflatoxin exposure to workers handling the grain during post-harvest storage and processing. Currently, no technologies are available to remove or detoxify these toxic and mutagenic fungal metabolites from contaminated rough rice. Pulsed light (PL) is a novel technology with the potential to degrade and detoxify aflatoxins in foods and their processing by-products. Rough rice was inoculated with Aspergillus flavus to produce aflatoxin B₁ (AFB₁) and B₂ (AFB₂) contamination, followed by PL treatments of 0.52 J/cm²/pulse for various durations. A PL treatment time of 80 s reduced AFB₁ and AFB₂ in rough rice by 75.0% and 39.2%, respectively; while a treatment time of 15 s reduced AFB₁ and AFB₂ in rice bran by 90.3% and 86.7%, respectively. Since PL treatments result in the degradation of aflatoxins in situ, the toxicity and mutagenic activity of the residual by-products of AFB₁ and AFB₂ after PL treatment were evaluated. Toxicity was estimated using the brine shrimp (Artemia salina) lethality assay and mutagenicity measured by the fluctuation test with Salmonella typhimurum tester strains TA98 and TA100. The mutagenic activity of AFB₁ and AFB₂ was completely eliminated by PL treatment, while the toxicity of these two aflatoxins was significantly decreased. The obtained results suggest that PL technology has a promising potential to degrade, detoxify, and inactivate the mutagenic activity of aflatoxins in rough rice and rice bran.     

Aflatoxin B1 decontamination by UV-mutated live and immobilized Aspergillus niger

The decontamination of Aflatoxin B₁ (AFB₁) by immobilized cells of a new mutant strain, prepared on a base of HSCAS (hydrated sodium calcium aluminosilicate), was studied. Novel strains were induced by UV irradiation, from which 50 were screened according to their degradation efficacy on AFB_1, compared with the wild strain (FS-Z1). The FS-UV1 strain exhibited highest degradation efficacy, which was confirmed by 18SrDNA to be Aspergillus niger. The results indicate that both immobilized cells and this mutant strain which are incubated for 48 h at 30 °C, would considerably remediate AFB₁ in nutrient broth culture, by 95.32% and 82.43%, respectively. By the application of samples of contaminated cottonseed meal, with results of 93.46%∼96.82%, the degradation rate was also validated. The results of Ames test indicate the mutagenic activity of treated AFB₁ is greatly abated, with treated controls. The Application of LC-q-TOFMS (liquid-chromatography, quadrupole, time-of-flight mass spectrometry) deduces the structure and molecular formulas of the degradation products. In the vivo study, the damages of photomicrographic evidence are decreased in kidney and liver and the serum biochemical parameters is improved, in response to preventative treatment with immobilized cells. This is the application of HSCAS-prepared, immobilized A. niger cells to degrade AFB₁ of contaminated samples. The investigation in this paper offers a novel path for economical, time-saving biodegradation of AFB₁ in foods and feeds.     

The in vitro ability of different Saccharomyces cerevisiae – Based products to bind aflatoxin B1

The purpose of this study was to evaluate the ability of Saccharomyces cerevisiae (SC) – based products from sugar cane fermentation (dried yeast – DY, autolyzed yeast – AY, cell wall – CW) and from beer fermentation (brewery dehydrated residue – BDR) to bind aflatoxin B₁ (AFB₁) in phosphate buffer saline (PBS) spiked with 0.5 μg AFB₁ mL⁻¹. All SC cells were heat-killed (121 ° C, 10 min) and then used for checking the effect of contact time (5, 10, 20 and 30 min) on toxin binding capacity. Compared to the CW and BDR treatments, DY and AY had higher (p < 0.05) capability to bind AFB₁ in PBS, although there were no differences (p > 0.05) among the contact times for any product evaluated. The mean percentages of AFB₁ bound by the DY were higher than AY, varying from 96.5% to 99.3% and from 90.4% to 97.5%, respectively, although the differences were not significant (p > 0.05). The SC-based products from sugar cane fermentation have a potential application for reducing levels of AFB₁ in contaminated food products. However, additional studies are needed to investigate the mechanisms involved in the removal process of toxin by SC and factors that affect toxin sequestration aiming the commercial application in food industry.     

Aflatoxigenic fungi and aflatoxins occurrence in sultanas and dried figs commercialized in Brazil

The presence of aflatoxins, Aspergillus flavus and Aspergillus parasiticus in dried fruits was investigated. A total of 62 dried fruit samples were analyzed (24 black sultanas, 19 white sultanas and 19 dried figs). A total of 10 A. flavus isolates were found, nine in one white sultana sample (corresponding to 18% infection) and one isolate in dried figs (2%), and all of them were aflatoxin B₁ and B₂ producers. A. parasiticus was not found. Aflatoxins were detected in 3 of 19 (16%) white sultana samples analyzed and, the limits were not higher than 2.0 μg/kg. In dried figs 11 of 19 (58%) samples were contaminated with aflatoxins and, with exception of one sample that was contaminated with 1500 μg/kg of B₁ aflatoxin, the others had less than 2.0 μg/kg. Neither aflatoxigenic or aflatoxins contaminated black sultanas.