Aflatoxin B1 Concentration Research Articles

The Efficiency of Aloe vera Gel Extract in Inhibiting the Growth of Aspergillus flavus Fungus Associated with Imported and Domestic Rice Grains in Iraq and its Ability to Reduce Aflatoxin B1 Production

Al-Hamiri, K.A.A. and H.Z. Hussein. 2022. The Efficiency of Aloe vera Gel Extract in Inhibiting the Growth of Aspergillus flavus Fungus Associated with Imported and Domestic Rice Grains in Iraq and its Ability to Reduce Aflatoxin B1 Production. Arab Journal of Plant Protection, 40(2): 164-168. https://doi.org/10.22268/AJPP-040.2.164168 The study aimed to evaluate the efficiency of different concentrations of Aloe vera gel extract in inhibiting the growth of A. flavus on potato dextrose agar (PDA) culture medium, as well as evaluating the efficiency of the extract in inhibiting the growth of A. flavus and reducing Aflatoxin B1 (AFB1) production in rice grains. The results obtained showed that the concentrations 1, 2, 3, and 4% of Aloe vera gel extract caused variable inhibition rates of A. flavus growth on PDA culture medium; of 97, 100, 5.88 and 17.64%, respectively. The best concentration from the laboratory experiment, (2%) was used, to evaluate its efficiency in inhibiting the growth of A. flavus on rice grains during storage and reduced AFB1 production by 86.5%, from 21.2 ppb in the control to 2.86 ppb in the treatment using HPLC high- performance liquid chromatography. The same treatment reduced AFB1 concentration in rice grains contaminated with AFB1 by 74.7%, from 22.88 ppb in control to 5.78 ppb in the extract treatment. Keywords: A. flavus, mycotoxins, aflatoxin B1, Aloe vera, food, feed, toxicity

Assessment of aflatoxin M1 and B1 in some dairy products with referring to the analytical performances of enzyme-linked immunosorbent assay in comparison to high-performance liquid chromatography.

Background and Aim:Aflatoxin M1 (AFM1) is a major fungal metabolite found in milk coming from aflatoxin B1 (AFB1) contaminated rations and is subsequently present in milk-based products demonstrating a serious public health hazard. This study aimed to investigate the levels of AFM1 and AFB1 in milk and some dairy products consumed widely by infants and children.Materials and Methods:This study investigated the incidence of AFM1 in 105 samples of processed cheese, Ras cheese, and raw milk (35 of each) retailed in the Egyptian markets. The degree of sensitivity and accuracy was evaluated using the enzyme-linked immunosorbent assay (ELISA) method followed by the estimation of the positive samples using the high-performance liquid chromatography (HPLC) with fluorescence detection. Mold count was determined in the examined samples by investigating AFB1 content using HPLC.Results:AFM1 was found in all investigated Ras cheese, raw milk, and 82.86% of the processed cheese samples with mean values of 51.05±6.19, 40.27±3.996, and 10.77±1.39 ng/kg, respectively. Moreover, there was statistically no significant difference between AFM1 levels in the core and crust parts of the tested Ras cheese. AFM1 contaminated Ras cheese and raw milk samples were 48.57% and 25.71%, which exceeded the European and Egyptian tolerance levels. Results showed an acceptable correlation between ELISA and HPLC methods with no significant difference (p>0.05). Alternatively, none of the examined samples proved to be contaminated with AFB1 despite the presence of mold with mean counts of 3.79±3.29, 4.39±4.34, and 4.84±4.29 log CFU/g in the examined processed cheese, Ras cheese, and raw milk samples, respectively.Conclusion:Therefore, it is urgent to regularly inspect the contamination of animal feeds with AFB1 and apply special measures and novel techniques to protect the feed and food from public health hazards.

Evaluation of Aflatoxin B1 in poultry feeds marketed in Nsukka agricultural zone, Enugu State, South Eastern Nigeria

Aflatoxin contamination of poultry feeds is a major challenge to profitable poultry productivity and trade. This study was carried out to evaluate the levels of aflatoxin B1 (AFB1) contamination of poultry feeds commonly sold in Nsukka, Enugu State, Nigeria. A total of 48 representative feed samples, comprising 24 toll-milled and 24 commercial feeds, were collected. aflatoxin B1 was detected in all (100%) the samples analysed using Indirect Competitive ELISA technique at various concentrations, with AFB1 concentrations of toll-milled and commercial feeds samples ranging from 2.5 – 473.8 ppb and 1.1 – 1683.2 ppb, respectively. The mean AFB1 concentration (77.69 ± 19.36 ppb) of toll-milled feed samples was significantly less (p ≤ 0.05) than the mean AFB1 concentration of commercial feeds brands (231.10 ± 71.1 ppb). The mean AFB1 concentration of commercial brand A feeds (12. 11 ± 3.25 ppb) was significantly less (p < 0.05) than the mean concentrations of commercial brand B feeds (385.91 ± 152 ppb) and brand C feeds (425.90 ± 97.93 ppb). The toll-milled and commercial feeds samples evaluated showed that 79.17% and 70.8% of the feeds, respectively, had AFB1 concentrations above the United State Food and Drugs Administration action value, 20 ppb. The levels of AFB1 contaminations in the feed samples studied were high, and thus make the feeds unsafe for poultry consumption. Therefore, there is need for routine screening and monitoring of AFB1 in poultry feeds marketed in this area to avoid high levels of AFB1 in feeds and the subsequent accumulation in the poultry products.

Optimization of gluten-free bread production with low aflatoxin level based on quinoa flour containing xanthan gum and laccase enzyme

This study was aimed to develop a new cereal-based product using quinoa flour, xanthan gum, and laccase and also to evaluate their effects on the quality characteristics of gluten-free bread (GFB). Experimental design method was applied for optimization of gluten-free formulation. The effects of three variables of quinoa flour (0–50%), laccase activity (0–2 U/g flour), and xanthan gum (0–0.5%) on the contents of total aflatoxin (TAF) and aflatoxin B1 (AFB1), color indices (L*, a*, and b*), and texture properties (hardness, cohesiveness, and springiness) of GFB were evaluated. The results showed that quinoa flour and laccase enzyme significantly reduced TAF and AFB1 (p < 0.05). The lowest AFB1 level (3.67 ± 0.96 ng/g) in the GFB formulation containing quinoa flour (40%), laccase enzyme (2.0 U/g), and xanthan gum (0.46%) was very close to the predicted amount (3.66 ± 0.96 ng/g). Quinoa flour significantly reduced the L* and a* values and increased b* value and improved the texture parameters. Laccase enzyme also improved color indices and texture properties. Therefore, the use of laccase enzyme and quinoa flour is recommended based on the desired effect on the quality characteristics of GFB.

Levels of filamentous fungi and selected mycotoxins in leafy and fruit vegetables and analysis of their potential health risk for consumers

The aim of the study was to determine the presence, concentration and generic composition of filamentous fungi. Considering the significant role of mycotoxins in the pathogenicity of fungal contaminants of vegetables, the scope of the study was extended by determination of aflatoxins and deoxynivalenol.In the years 2019-2020, samples of vegetables (lettuce, spinach, tomato, red pepper) collected on conventional farms located in eastern Poland were subjected to mycological examination. The concentration and species composition of filamentous fungi were determined by the method of plate dilutions on malt agar. The isolated strains were identified with the use of macroscopic and microscopic methods. Samples were also analyzed for the presence of aflatoxin B1 (AFB1), total aflatoxin (AFT) and deoxynivalenol (DON) using the immunoenzymatic ELISA method.The median concentrations of filamentous fungi ranged from 2.778-3.204 log10 CFU g -1. Overall, 40 fungal species were identified in the examined vegetables, of which 38 are classified as potentially pathogenic for humans. The mean prevalence values for AFB1 and AFT were moderate or high (16.0-60.0% and 57.8-75.6%, respectively) and very low for DON (0-2.2%). The median concentrations of filamentous fungi, AFB1 and AFT were distinctly greater in leafy vegetables than on non-leafy tomato and pepper fruits, and the differences were highly significant (P<0.001).The levels of filamentous fungi and mycotoxins in Polish vegetables could be classified as moderate or low. The abundant presence of species with various pathogenic abilities may pose a risk for some categories of people consuming raw vegetables, mostly for immuno-compromised persons or atopics susceptible to food allergy caused by ingested moulds.

Regulation of Ru(bpy)32+ Electrochemiluminescence Based on Distance-Dependent Electron Transfer of Ferrocene for Dual-Signal Readout Detection of Aflatoxin B1 with High Sensitivity.

Ferrocene (Fc) is a common quencher of Ru(bpy)32+ luminescence. However, interactions between Fc and Ru(bpy)32+ can be extremely complicated. In this work, we reported the first use of Fc to regulate the electrochemiluminescence (ECL) of Ru(bpy)32+ by tuning the length of the DNA sequence between Fc and the luminophore of nitrogen-doped graphene quantum dots-Ru(bpy)32+-doped silica nanoparticles (SiO2@Ru-NGQDs). The ECL of SiO2@Ru-NGQDs was depressed when the distance between Ru(bpy)32+ and Fc was less than 8 nm; a stronger ECL was observed when the distance was more than 12 nm. The switching of the ECL of Ru(bpy)32+ by Fc was attributed to the electron transfer mechanism, in which Fc participated in the redox of Ru(bpy)32+ for "signal-off" ECL; this favored electron transfer at the electrode fabricated with an Fc-labeled aptamer (Fc-apt) and SiO2@Ru-NGQDs for "signal-on" ECL depending on the length of the DNA sequence. Here, a dual-signal readout aptasensor for aflatoxin B1 (AFB1) detection was developed via the enhanced ECL of SiO2@Ru-NGQDs by Fc-apt. The redox currents of Fc and the ECL of Ru(bpy)32+ were simultaneously collected as yardsticks, and both decreased with higher concentrations of AFB1. The aptasensor allowed linear ranges of 3 × 10-5 to 1 × 102 ng mL-1 for ECL mode and 1 × 10-3 to 3 × 103 ng mL-1 for electrochemical mode. Our work provides insight into the interactions between Fc and Ru(bpy)32+. The dual-signal readout strategy is a potential platform for the versatile design of aptasensors.

Occurrence of Aflatoxin B1 in Animal Feed Collected from the Northeastern Area of Morocco

The carry-over of contaminants from feed to animal products is an important issue in the animal production chain, therefore, the quality control of those animal products should include the control of the animal feed. The current study was carried out to assess the contamination levels of three types of animal feed (dairy animal feed, poultry feed, and fish feed) by Aflatoxin B1. A total of 68 animal feed samples were collected from the Northeastern Moroccan area (Tangier-Tétouan-AL Hoceima). The samples were extracted with a mixture of acetone/water. The sample extractions were filtered, diluted with phosphate-buffered saline, and applied to an immunoaffinity column. Aflatoxin B1 was eluted with methanol then analyzed by high-performance liquid chromatography with fluorescence detection, after post-column photochemical derivatization. The analytical results for the level of Aflatoxin B1 in the animal feed samples revealed an average presence of 44.12% for all analyzed samples. The concentrations were between 1.02 and 13.59 µg/Kg, with a mean value of 4.08 ± 3.11 µg/Kg. The results indicated that there was a significant difference across the three types of animal feeds regarding the concentrations of Aflatoxin B1.

Dysregulation of Intestinal Physiology by Aflatoxicosis in the Gilthead Seabream (Sparus aurata).

Aflatoxin B1 (AFB1) is a mycotoxin often present in food. This study aimed to understand the physiological effects of AFB1 on the seabream (Sparus aurata) gastrointestinal system. In a first in vitro approach, we investigated ion transport using the short-circuit current (Isc) technique in Ussing chambers in the anterior intestine (AI). Application of apical/luminal AFB1 concentrations of 8 and 16 μM to healthy tissues was without effect on tissue transepithelial electrical resistance (TER), and apparent tissue permeability (Papp) was measured using fluorescein FITC (4 kD). However, it resulted in dose-related effects on Isc. In a second approach, seabream juveniles fed with different AFB1 concentrations (1 and 2 mg AFB1 kg−1 fish feed) for 85 days showed significantly reduced gill Na+/K+-ATPase (NKA) and H+-ATPase (HA) activities in the posterior intestine (PI). Moreover, dietary AFB1 modified Isc in the AI and PI, significantly affecting TER in the AI. To understand this effect on TER, we analyzed the expression of nine claudins and three occludins as markers of intestinal architecture and permeability using qPCR. Around 80% of the genes presented significantly different relative mRNA expression between AI and PI and had concomitant sensitivity to dietary AFB1. Based on the results of our in vitro, in vivo, and molecular approaches, we conclude that the effects of dietary AFB1 in the gastrointestinal system are at the base of the previously reported growth impairment caused by AFB1 in fish.

Effects of Lactic Acid Bacterial Inoculants on Fermentation Quality, Bacterial Community, and Mycotoxins of Alfalfa Silage under Vacuum or Nonvacuum Treatment

To investigate the effects of lactic acid bacterial (LAB) inoculants and vacuuming on the fermentation quality and bacterial community, alfalfas were ensiled with or without a commercial LAB YX or Lactobacillus plantarum strain ZZUA493 for 10, 30, 60, and 90 days while undergoing either vacuum (V) or nonvacuum (NV) treatment. At 90 days, analysis of the microbial community by high-throughput sequencing was performed, and contents of aflatoxin B1 and deoxynivalenol (DON) mycotoxins in alfalfa silage were determined. In all inoculated alfalfa silage, irrespective of V or NV treatment, lactic acid (LA) content increased, pH (p < 0.05), and ammonia nitrogen (p < 0.05) content decreased, and no butyric acid was detected. Lactobacillus or Pediococcus became the dominant genus, and the abundance of Garciella decreased in alfalfa silage with the addition of either inoculant. The LAB inoculants YX and ZZUA493 helped reduce the mycotoxin content in alfalfa silage. The abundance of Garciella in the control and DON content in all alfalfa silage groups were higher (p < 0.05) in NV than V. In summary, LAB inoculants and vacuuming had a positive influence on alfalfa silage quality, and LAB inoculants were effective in reducing mycotoxins in silage alfalfa.

Effects of hexanoic acid on microbial communities, fermentation, and hygienic quality of corn silages infested with toxigenic fungi.

This study aims to reveal the effects of hexanoic acid on the microbial communities, fermentation, and the hygienic quality of corn silages with or without fungal infection. Fungal-infested (FI) and non-infested (NFI) whole-crop corn samples were separately ensiled without (control, CON) or with hexanoic acid (Hex, 90% purity) at 0.2g·kg-1 fresh weight (FW). The addition of Hex accelerated the pH decline during the first 5 days of ensiling regardless of fungal infestation. The lactic acid (LA) concentration in Hex silages was lower than that in CON during 45 days of ensiling; however the FI-Hex silage had the highest LA concentration among treatments on day 90. The Hex silage showed lower aflatoxin B1 (AFB1 ), zearalenone (ZEA), and deoxynivalenol (DON) concentrations than CON for FI silages. On day 5, the addition of Hex decreased the relative abundance of Klebsiella, Pantoea, and Enterobacter compared with CON, regardless of fungal infestation. This inhibitory effect lasted until day 90 for NFI silages but disappeared for FI silages on day 90. The fungal infestation resulted in the accumulation of Candida (34.05%) and Wickerhamomyces (19.46%). Hex decreased the relative abundance of Asperigillus, Issatchenkia, and Penicillium for NFI silages on day 5; however, its inhibitory effects were not observed in FI silages on day 5. Fungal infestation was associated with poor fermentation and hygienic quality of corn silage. Adding Hex accelerated the pH decline and maintained the antifungal activity until 90 days of ensiling, attenuating adverse effects of fungal infestation on the fermentation and preventing the accumulation of mycotoxins in corn silages. © 2021 Society of Chemical Industry.

Aflatoxin B1 in imported cinnamon consumed in the Yazd province of Iran

ABSTRACT Aflatoxins are toxic secondary metabolites produced mainly by Aspergillus flavus and A. parasiticus, which are fungal contaminants found in several foodstuffs, including spices. In this study 40 cinnamon samples were collected in November and December 2020 in the Iranian province of Yazd and analysed for the presence of aflatoxin B1 (AFB1) by high performance liquid chromatography. Seven out of 40 (17.5%) samples were contaminated with AFB1 at levels ranging from 0.59 to 5.8 μg/kg. In addition, 2.5% of cinnamon samples contained AFB1 concentrations above the maximum level of 5 μg/kg, as established by the Iranian national standard. Due to the harmful effects of aflatoxins, even at low amounts, these can cause serious chronic health problems. Therefore, continuous control to avoid AFB1 contamination in foodstuffs is required.

Application of SWIR hyperspectral imaging coupled with chemometrics for rapid and non-destructive prediction of Aflatoxin B1 in single kernel almonds

Almonds are highly susceptible to Aflatoxin B1 (AFB1) contamination, which can result in significant economic losses. Current detection techniques are destructive, time consuming and unfit for in-line application. This study investigated the potential of hyperspectral imaging in the near infrared (NIR) range (900–1700 nm) to develop a rapid and non-destructive protocol for determination of AFB1 content of single almond kernels. Almond kernels were treated to varying AFB1 concentration by artificial infection using standard AFB1 solution and used for Experimentation. Reference AFB1 concentration and their association with the spectral data were modelled using partial least squares regression (PLSR) combined with suitable spectral preprocessing techniques. Superior models were obtained with full-spectrum regression models with R2 and RMSEP values of 0.958 and 0.089 μg/g, respectively. Competitive-adaptive reweighted sampling (CARS) was used to select the feature wavelengths for rapid quantification of AFB1 at commercial scale. Multiple linear regression (MLR) models were developed using the selected wavelengths for its applicability in multispectral imaging systems. Results showed that the MLR model achieved good prediction capabilities with R2 and RMSEP values of 0.948 and 0.090 μg/g, respectively. The results demonstrated that hyperspectral imaging had potential for rapid and nondestructive determination of AFB1 concentration in single kernel almonds.

Development of a colorimetric aptasensor for aflatoxin B1 detection based on silver nanoparticle aggregation induced by positively charged perylene diimide

A sensitive colorimetric aptasensor for rapid quantification of aflatoxin B1 (AfB1) has been successfully developed. The sensing strategy is based on the aggregation and localized surface plasmon resonance (LSPR) of silver nanoparticles (AgNPs) that involves interactions of a specific aptamer, positively charged perylene diimide (PCPD), and AgNPs nanoprobes. The aptamer can explicitly bind to AfB1, resulting in a conformational change of the aptamer, leading to a dissociation of the PCPD-aptamer complex. Eventually, the released PCPD induces aggregation of AgNPs, producing a new color tone derived from the surface plasmon wavelength shift of AgNPs. The absorbance ratio between 520 nm and 393 nm (A520/393 nm) of AgNPs aggregation has been applied to calculate AfB1 concentration in the sample. A high concentration of AfB1 displays the increasing A520/393 nm. Inversely, a low concentration of AfB1 exhibits the decreasing A520/393 nm. A calibration graph of the aptasensor exhibits excellent linear response to the AfB1 amount in the range of 0.2–6.0 ng/mL. A detection limit for AfB1 determination is 0.09 ng/mL with very low cross-reactivity from other mycotoxins, signifying high selectivity. Furthermore, the proposed method has been successfully applied to determine AfB1 in peanut, corn, and chicken feed samples. Obtained recoveries are more significant than 80%, with RSD lower than 10%. Hence, an innovative aptasensor can be used as an alternative method for quantifying AfB1 in real samples.

Quantitative detection of Aflatoxin B1 by subpixel CNN regression

Aflatoxin is a highly toxic substance dispersed in peanuts, which seriously harms the health of humans and animals. In this paper, we propose a new method for aflatoxin B1(AFB1) detection inspired by quantitative remote sensing. Firstly, we obtained the relative content of AFB1 at the sub-pixel level by subpixel decomposition (endmember extraction, nonnegative matrix decomposition). Then we modified the transfer learning models (LeNet5, AlexNet, VGG16, and ResNet18) to construct a deep learning regression network for quantitative detection of AFB1. There are 67,178 pixels used for training and 67,164 pixels used for testing. After subpixel decomposition, each aflatoxin pixel was determined to contain content, and each pixel had 400 hyperspectral values (415–799 nm). The experimental results showed that, among the four models, the modified ResNet18 model achieved the best effect, with R2 of 0.8898, RMSE of 0.0138, and RPD of 2.8851. Here, we implemented a sub-pixel model for quantitative AFB1 detection and proposed a regression method based on deep learning. Meanwhile, the modified convolution classification model has high predictive ability and robustness. This method provides a new scheme in designing the sorting machine and has practical value.

Lignin and organic free radicals in maize (Zea mays L.) seeds in response to aflatoxin B1 contamination: an optical and EPR spectroscopic study.

Aflatoxin B1 (AFB1 ) is the most dangerous of the mycotoxins that contaminate cereal seeds naturally. A stress lignin formation is linked with the accumulation of reactive oxygen species causing a change in the redox status and formation of stable organic radicals, constituting the first layer of defense. The relationship between AFB1 and changes in lignin organic free radicals in seeds is not known, nor is the part of the seed that is more targeted. Using optical and electron paramagnetic resonance spectroscopy, we investigated AFB1 -induced changes in lignin and organic free radicals in seeds, and whether the inner and outer seed fractions differ in response to increasing AFB1 . Different changes in the content of lignin and free radicals with increasing AFB1 concentrations were observed in the two seed fractions. There was a significant positive linear correlation (R=0.9923, P=0.00005) between lignin content and AFB1 concentration in the outer fraction, and no correlation between the lignin content and the AFB1 concentration in the inner fraction. We found a positive correlation between the area of the green spectral emission component (C4) and the AFB1 concentration in the outer fraction. To the best of our knowledge, the results showed, for the first time, that maize seed fractions respond differently to aflatoxin with regard to their lignin and organic free radical content. Lignin content and (C4) area may be reliable indicators for the screening of lignin changes against AFB1 content in the seeds, and thus for seed protection capacity. © 2021 Society of Chemical Industry.

Photocatalytic detoxification of aflatoxin B1 in an aqueous solution and soymilk using nano metal oxides under UV light: Kinetic and isotherm models

Aflatoxin B1 (AFB1) is the greatest toxic aflatoxin, contaminating a substantial portion of the global food supply. In this work, the effects of nanoparticles (NPs) type (ZnO, Fe2O3, MnO2 and CuO), contact time (10–90 min), initial concentration of AFB1 (10–30 μg/L) and NPs concentration (0.02–0.12 mg/mL) on the photocatalytic detoxification of AFB1 were investigated in aqueous solution under UV light. These NPs were successfully prepared and confirmed with energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The findings indicated complete removal of 10 μg/L AFB1 by 0.10 mg/mL ZnO NPs aqueous solution after 60 min UV irradiation. The detoxification results of AFB1 were adequately compatible with the pseudo-first-order kinetic and Langmuir isotherm models. Two AFB1 degradation products with m/z values of 331 and 279 were identified by mass spectrometry. Application of this NP in soymilk completely removed AFB1 under UV irradiation with no significant effect on its overall acceptability. Therefore, it can be considered as a promising approach to reduce AFB1 in contaminated liquid foods.

Mycobiota Isolation and Aflatoxin B1 Contamination in Fresh and Stored Sesame Seeds from Rainfed and Irrigated Zones of Punjab, Pakistan

This study was carried out to evaluate the prevalence of mycobiota and aflatoxin (AF) B1 contamination in sesame seeds from rainfed and irrigated zones of the Punjab, Pakistan. For this purpose, 100 sesame seed samples were collected directly from the fields of major sesame-producing areas in rainfed and irrigated zones. The agar plate method was used for isolation of mycobiota, and thin-layer chromatography was used to determine AFB1 concentrations. Seed samples were then stored for 12 months. After 12 months, the seeds were again analyzed for mycobiota and AFB1 for comparison. All samples were positive for fungal growth under fresh and stored conditions. Twenty-one fungal species of 10 genera were isolated. Aspergillus flavus was the most prevalent contaminant found in fresh and stored sesame seeds from rainfed and irrigated zones, followed by Aspergillus niger, Alternaria alternata, and Fusarium oxysporum. The least prevalent fungi were Aspergillus ochraceus and Cladosporium oxysporum. Analysis revealed that 92% of fresh and 99% of stored seed samples were contaminated with AFB1. In the rainfed zone, 88% of fresh and 100% of stored seed samples were contaminated with AFB1, with mean concentrations of 15.74 and 33.8 ppb, respectively. In the irrigated zone, 96% of fresh and 98% of stored seed samples were contaminated with AFB1, with mean concentrations of 20.5 and 27.56 ppb, respectively. AFB1 concentrations >20 ppb were found in 20% of fresh and 100% of stored seeds samples from the rainfed zone and in 28% of fresh and 60% of stored samples from the irrigated zone and thus were not fit for human consumption as per the maximum limit (20 ppb) assigned by the U.S. Food and Drug Administration and the Food and Agriculture Organization of the United Nations. This report is the first on the mycobiota and AFB1 contamination in sesame seeds from rainfed and irrigated zones of the Punjab, Pakistan. These baseline data are an initial step in the effort to deal with this significant food safety issue.

Effect of Lactic Acid Bacteria on the Fermentation Quality and Mycotoxins Concentrations of Corn Silage Infested with Mycotoxigenic Fungi.

This study was conducted to evaluate the effect of lactic acid bacteria (LAB) on fermentation quality, mycotoxin concentrations, and microbial communities of whole-crop corn silages infested with mycotoxigenic fungi. Cultured spores (106 cfu/mL) of mycotoxigenic Aspergillus flavus and Fusarium graminearum were sprayed (5 mL) on corn forage on 27 July and 10 August 2018. On 21 August 2018, sprayed (FI; 3 plots) and unsprayed (NFI; 3 plots) corn forage were harvested at the 1/2 kernel milk line stage, followed by chopping and ensiling without inoculants (CON), or with Lactobacillus buchneri (LB, 1 × 106 cfu/g FW), Lactobacillus plantarum (LT, 1 × 106 cfu/g FW), or L. buchneri + L. plantarum (BT: both L. buchneri and L. plantarum applied at 0.5 × 106 cfu/g FW). After 90 d of ensiling, FI silages had a higher (p < 0.05) pH value and higher acetic acid (ACA), ethanol, and ammonia nitrogen (ammonia N) concentrations, but lower (p < 0.05) lactic acid (LA) concentrations than NFI silage. The inoculants decreased pH and increased LA concentration and LA/ACA compared with CON. The aflatoxin B1 (AFB1) was only detected in FI fresh corn and silages; ensiling decreased (p < 0.05) AFB1 concentration compared with fresh corn, and LB and BT decreased AFB1 concentration compared with CON. The zearalenone (ZEN), deoxynivalenol (DON), and fumonisin B1 (FB1) concentrations were similar (p < 0.05) for NFI silages, while ZEN concentration in BT was the lowest (p < 0.05) among all FI silages; DON and FB1 concentrations in LB, LT, and BT silages were significantly lower (p < 0.05) than those of CON in FI silages. The fungal infestation increased the bacterial and fungal diversity of silages compared with NFI silages. The FI silages had a higher relative abundance (RA) of Lactobacillus, Weissella, Wickerhamomyces, Pichia, and Epicoccum than the corresponding NFI silages. The RA of Aspergillus and Fusarium markedly decreased after 90 d of ensiling, and the inoculation expanded this trend irrespective of fungal infestation. The Penicillium in FI silages survived after 90 d of ensiling, while the inoculants decreased the RA of Penicillium. Inoculants mitigate the adverse effects of fungal infestation on corn silage quality by changing the bacterial and fungal communities.

Dual-ratiometric electrochemical aptasensor enabled by programmable dynamic range: Application for threshold-based detection of aflatoxin B1

Aptamer-based sensor with high-specificity typically has a fixed linear range due to the host-guest binding. To expand the dynamic range for multiple scenarios, we report here a dual-ratiometric electrochemical aptasensor that integrates two aptamer profiles with varied affinity into a single sensing interface for aflatoxin B1 (AFB1) detection. Using functional aptamer as recognition element and generator of signals, we fabricate the dual-ratiometric aptasensor with anthraquinone loaded reduced graphene oxide (AQ-rGO), methylene blue labeled hairpin DNA (MB-DNA), and ferrocene labeled linear aptamer (Fc-apt), using MB and Fc probes to work in tandem while AQ as reference. The current of Fc (IFc) is used to detect the low-concentration analyte, and that of MB (IMB) varies when the concentration of AFB1 reaches a threshold. The threshold switch for IMB could be tuned by engineering the quantity ratio of Fc-apt and MB-DNA (a ratio of 1:1 is used here). The aptasensor can rapidly achieve the positive (+)/negative (-) detection of AFB1 with a threshold concentration of 10 pg mL-1, while the quantitative detection employs the ratio of current of AQ, MB, and Fc (i.e., IAQ/IMB and IAQ/IFc) as yardsticks, offering two linear ranges of 10-106 and 10-2-5 × 104 pg mL-1, respectively. The aptasensor is successfully used to monitor the amount of AFB1 in a 7-days mildew process of peanut. Such a protocol opens a new way for the design of sensors with the programmable linear range in the advanced biological and chemical sensing.

A novel colorimetric biosensor for sensitive detection of aflatoxin mediated by bacterial enzymatic reaction in saffron samples

Aflatoxin is regarded as the potent carcinogenic agent which is secreted from fungi and present in some food products. So far, many detection methods have been developed to determine the trace amounts of aflatoxin in foods. In the present study a colorimetric competitive assay for detection of aflatoxin B1 (AFB1) has been developed based on interaction of gelatin functionalized gold nanoparticles (AuNPs@gelatin) in specific enzymatic reaction. Bacterial supernatant containing gelatinase enzyme were used as the substrate that could digest the coated gelatin on the surface of AuNPs and following in the presence of NaCl medium ingredient resulted to color change of AuNPs colloidal solution from red to purple. It was observed that with addition of aflatoxin to the bacterial supernatant, aflatoxin could interfere in aggregation of AuNPs and inhibited the process which subsequently prevent the expected color change induced by AuNPs aggregation. The supernatant containing AuNPs were investigated to analyze their induced surface plasmon resonance spectra through UV–visible spectroscopy. The absorption values were directly proportional with the applied AFB1 concentration. The experiment conditions including incubation time, AuNPs concentration and pH were investigated. The obtained results showed that through this approach we could detect the AFB1 in a linear range from 10 to 140 pg ml−1, with detection limit of 4 pg ml−1. Real sample assay in saffron samples showed recoveries percentage of 92.4%–95.3%. The applied approach proposed simple, cost effective and specific method for detection of AFB1 toxin in food samples.