Assessment of the Effect of Satureja montana and Origanum virens Essential Oils on Aspergillus flavus Growth and Aflatoxin Production at Different Water Activities

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Aflatoxin contamination of foodstuffs poses a serious risk to food security, and it is essential to search for new control methods to prevent these toxins entering the food chain. Several essential oils are able to reduce the growth and mycotoxin biosynthesis of toxigenic species, although their efficiency is strongly influenced by the environmental conditions. In this work, the effectiveness of Satureja montana and Origanum virens essential oils to control Aspergillus flavus growth was evaluated under three water activity levels (0.94, 0.96 and 0.98 aw) using a Bioscreen C, a rapid in vitro spectrophotometric technique. The aflatoxin concentrations at all conditions tested were determined by HPLC-FLD. Aspergillus flavus growth was delayed by both essential oil treatments. However, only S. montana essential oil was able to significantly affect aflatoxin production, although the inhibition percentages widely differed among water activities. The most significant reduction was observed at 0.96 aw, which is coincident with the conditions in which A. flavus reached the highest levels of aflatoxin production. On the contrary, the treatment with S. montana essential oil was not effective in significantly reducing aflatoxin production at 0.94 aw. Therefore, it is important to study the interaction of the new control compounds with environmental factors before their application in food matrices, and in vitro ecophysiological studies are a good option since they provide accurate and rapid results.Peer reviewedFinal Published versio

Interacting Abiotic Factors Affect Growth and Aflatoxin B1 Production Profiles of Aspergillus flavus Strains on Pistachio-Based Matrices and Pistachio Nuts

© 2021 Baazeem, Garcia-Cela, Medina and Magan. This is an openaccess article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.Pistachio nuts are an economically important commodity produced by many countries. They can be colonized by mycotoxigenic fungi, especially Aspergillus flavus, resulting in contamination with aflatoxins (AFs), especially aflatoxin B1 (AFB1), a Class 1a carcinogen. The objectives were to examine the effect of interactions between the two key abiotic factors, temperature and water activity (aw) on (a) in vitro growth and AFB1 production by four strains of A. flavus isolated from pistachio nuts, on a milled pistachio nut medium modified ionically (NaCl) and non-ionically (glycerol) in the range 20–35°C and 0.995–0.85 aw, (b) colonization of layers of raw pistachio nuts stored at different interacting temperature x aw conditions and on relative AFB1 production and (c) develop models to produce contour maps of the optimal and marginal boundary conditions for growth and AFB1 production by up to 4 strains of this species. On pistachio nut-based media, optimum growth of four strains of A. flavus was at 0.98–0.95 aw and 30–35°C. Optimum AFB1 production was at 30–35°C and 0.98 aw. No significant differences in growth was found on ionic and non-ionically modified media. Colonization of layers of raw pistachio nuts was slower and contamination with AFB1 significantly less than in in vitro studies. Contour maps based on the pooled data for up to four strains (in vitro, in situ) showed the optimum and marginal conditions for growth and AFB1 production. These data can be used to identify those conditions which represent a high, intermediate or low risk of colonization and AFB1 contamination in the pistachio nut processing chain. These results are discussed in the context of the development of appropriate intervention strategies to minimize AFB1 contamination of this economically important commodity.Peer reviewedFinal Published versio

Electrospinning Alginate/Polyethylene Oxide and Curcumin Composite Nanofibers

© 2020 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/.Manufacturing a sodium alginate (SA) and polyethylene oxide (PEO) composite loaded with curcumin (CU) was accomplished in this study by using electrospinning. These composite nanofibers were crosslinked using trifluoroacetic acid (TFA) mechanically characterized along with the morphological properties of the composite nanofiber mesh. We were successful in manufacturing the composite nanofibers with a wide range of CU concentrations ranging from 10 to 40 wt%. Firstly, dissolved in a saturated water/CU solution it was added to SA/PEO blending, homogenized and electrospun. Mechanical properties were affected by both CU addition and the cross-linking process, resulting in a higher ultimate tensile stress (MPa) (from 4.3±2 to 15.1±2 at 10% CU) and Young modulus (GPa) (0.0076±0.003, 0.044±0.003 before and after TFA). CU was successfully encapsulated in the SA nanofibers and excellent mechanical properties were obtained. By using a biocompatible TFA crosslinking and the natural properties of alginate this nanofiber composite could potentially be used for filtering, environmental pollution control, food packaging and for tissue engineering.Peer reviewe

Influence of two garlic-derived compounds, propyl propane thiosulfonate (PTS) and propyl propane thiosulfinate (PTSO), on growth and mycotoxin production by Fusarium species in vitro and in stored cereals

Two garlic-derived compounds, Propyl Propane Thiosulfonate (PTS) and Propyl Propane Thiosulfinate (PTSO), were examined for their efficacy against mycotoxigenic Fusarium species (F. graminearum, F. langsethiae, F. verticillioides). The objectives were to assess the inhibitory effect of these compounds on growth and mycotoxin production in vitro, and in situ in artificially inoculated wheat, oats and maize with one isolate of each respectively, at different water activity (aw) conditions when stored for up to 20 days at 25 °C. In vitro, 200 ppm of either PTS or PTSO reduced fungal growth by 50–100% and mycotoxin production by >90% depending on species, mycotoxin and aw conditions on milled wheat, oats and maize respectively. PTS was generally more effective than PTSO. Deoxynivalenol (DON) and zearalenone (ZEN) were decreased by 50% with 80 ppm PTSO. One-hundred ppm of PTS reduced DON and ZEN production in wheat stored at 0.93 aw for 20 days, although contamination was still above the legislative limits. Contrasting effects on T-2/HT-2 toxin contamination of oats was found depending on aw, with PTS stimulating production under marginal conditions (0.93 aw), but at 0.95 aw effective control was achieved with 100 ppm. Treatment of stored maize inoculated with F. verticilliodies resulted in a stimulation of total fumonsins in most treatments. The potential use of such compounds for mycotoxin control in stored commodities is discussed

Influence of two garlic-derived compounds, propyl propane thiosulfonate (PTS) and propyl propane thiosulfinate (PTSO), on growth and mycotoxin production by Fusarium species in vitro and in stored cereals

Two garlic-derived compounds, Propyl Propane Thiosulfonate (PTS) and Propyl Propane Thiosulfinate (PTSO), were examined for their efficacy against mycotoxigenic Fusarium species (F. graminearum, F. langsethiae, F. verticillioides). The objectives were to assess the inhibitory effect of these compounds on growth and mycotoxin production in vitro, and in situ in artificially inoculated wheat, oats and maize with one isolate of each respectively, at different water activity (aw) conditions when stored for up to 20 days at 25 °C. In vitro, 200 ppm of either PTS or PTSO reduced fungal growth by 50–100% and mycotoxin production by >90% depending on species, mycotoxin and aw conditions on milled wheat, oats and maize respectively. PTS was generally more effective than PTSO. Deoxynivalenol (DON) and zearalenone (ZEN) were decreased by 50% with 80 ppm PTSO. One-hundred ppm of PTS reduced DON and ZEN production in wheat stored at 0.93 aw for 20 days, although contamination was still above the legislative limits. Contrasting effects on T-2/HT-2 toxin contamination of oats was found depending on aw, with PTS stimulating production under marginal conditions (0.93 aw), but at 0.95 aw effective control was achieved with 100 ppm. Treatment of stored maize inoculated with F. verticilliodies resulted in a stimulation of total fumonsins in most treatments. The potential use of such compounds for mycotoxin control in stored commodities is discussed

Solute and matric potential stress on Penicillium verrucosum : Impact on growth, gene expression and ochratoxin A p production

Funding Information: S.A. is grateful to the British Council and the Newton Musharraf Programme for financial support. Publisher Copyright: © 2020 Wageningen Academic Publishers. All rights reserved. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Penicillium verrucosum survives in soil and on cereal debris. It colonises grain during harvesting, drying and storage. There is no information on the relative tolerance of P. verrucosum to solute and matric stress in terms of colonisation, or on the biosynthetic toxin gene clusters or ochratoxin A (OTA) production. The objectives were to examine the effect of ionic and non-ionic solute and matric potential stress on (a) growth, (b) expression of two toxin biosynthetic genes otapksPV and otanrpsPV, and (c) OTA production by a strain of P. verrucosum. Optimum growth and OTA production were at-7.0 MPa (= 0.95 water activity, aw) and-1.4 MPa (= 0.99 aw), respectively, regardless of whether solute (Ψs) or matric (Ψm) stress was imposed. P. verrucosum was more sensitive to ionic solute stress (NaCl) with no growth at-19.6 MPa (=0.86 aw) while growth still occurred in the non-ionic solute (glycerol) and matric stress treatments. Relative gene expression of the biosynthetic genes using PCR (RT-qPCR) showed that the otapksPV gene was expressed over a wide range of ionic/non-ionic solute stress conditions (-1.4 to-14.0 MPa; = 0.99-0.90 aw). The highest expression was in the non-ionic Ψs stress treatments at-7.0 MPa (= 0.95 aw). However, the otanrpsPV gene was significantly up regulated under Ψm stress, especially with freely available water (-1.4 MPa = 0.99 aw). OTA production was significantly decreased as Ψs or Ψm stress were imposed. Limited OTA production occurred in the driest treatments under Ψs and Ψm stress respectively. The impact of these two types of stresses on the growth of P. verrucosum was quite different from that for OTA production. The results are discussed in the context of the life cycle and ecological characteristics of this species in contaminating cereals with OTA in the post-harvest phase of the cereal chain.Peer reviewedFinal Accepted Versio

Fungal diversity and metabolomic profiles in GM and isogenic non-GM maize cultivars from Brazil

The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. To view a copy of this licence, http://creativecommons.org/licenses/by/4.0/.There is little knowledge of the microbial diversity, mycotoxins and associated secondary metabolites in GM maize and isogenic non-GM cultivars (cvs). This study has quantified the microbial populations and dominant fungal genera in 6 cvs of each type representative of herbicide, pesticide or stacked resistance to both. The predominant mycotoxins and targeted metabolomics profiles were also compared between the two sets of cvs. This showed that the overall fungal populations were 8.8 CFUs g−1 maize. The dominant genera, isolated from maize samples, whether surface-sterilised or not, in all maize cvs were Fusarium, followed by Penicillium, Aspergillus and occasionally Cladosporium and Alternaria. The analysis of the targeted metabolomics showed that approx. 29 different metabolites were detected. These were dominated by fumonisins and minor Penicillium spp. metabolites (questiomycin A and rugulovasine A). Interestingly, the range and number of mycotoxins present in the GM cvs were significantly lower than in the non-GM maize samples. This suggests that while the fungal diversity of the two types of maize appeared to be very similar, the major contaminant mycotoxins and range of toxic secondary metabolites were much lower in the GM cvs.Peer reviewedFinal Published versio

Fusarium graminearum in stored wheat: use of CO2 production to quantify dry matter losses and relate this to relative risks of Zearalenone contamination under interacting environmental conditions

Zearalenone (ZEN) contamination from Fusarium graminearum colonization is particularly important in food and feed wheat, especially during post-harvest storage with legislative limits for both food and feed grain. Indicators of the relative risk from exceeding these limits would be useful. We examined the effect of different water activities (aw; 0.95–0.90) and temperature (10–25 °C) in naturally contaminated and irradiated wheat grain, both inoculated with F. graminearum and stored for 15 days on (a) respiration rate; (b) dry matter losses (DML); (c) ZEN production and (d) relationship between DML and ZEN contamination relative to the EU legislative limits. Gas Chromatography was used to measure the temporal respiration rates and the total accumulated CO2 production. There was an increase in temporal CO2 production rates in wetter and warmer conditions in all treatments, with the highest respiration in the 25 °C × 0.95 aw treatments + F. graminearum inoculation. This was reflected in the total accumulated CO2 in the treatments. The maximum DMLs were in the 0.95 aw/20–25 °C treatments and at 10 °C/0.95 aw. The DMLs were modelled to produce contour maps of the environmental conditions resulting in maximum/minimum losses. Contamination with ZEN/ZEN-related compounds were quantified. Maximum production was at 25 °C/0.95–0.93 aw and 20 °C/0.95 aw. ZEN contamination levels plotted against DMLs for all the treatments showed that at ca. 1.0% DML, the risk was high. This type of data is important in building a database for the development of a post-harvest decision support system for relative risks of different mycotoxins

Determining future aflatoxin contamination risk scenarios for corn in Southern Georgia, USA using spatio-temporal modelling and future climate simulations

© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Aflatoxins (AFs) are produced by fungi in crops and can cause liver cancer. Permitted levels are legislated and batches of grain are rejected based on average concentrations. Corn grown in Southern Georgia (GA), USA, which experiences drought during the mid-silk growth period in June, is particularly susceptible to infection by Aspergillus section Flavi species which produce AFs. Previous studies showed strong association between AFs and June weather. Risk factors were developed: June maximum temperatures > 33 °C and June rainfall  33 °C and rainfall < 50 mm increased and then plateaued for both emissions scenarios. The percentage of years thresholds were exceeded was greater for RCP 8.5 than RCP 4.5. The spatial distribution of high-risk counties changed over time. Results suggest corn growth distribution should be changed or adaptation strategies employed like planting resistant varieties, irrigating and planting earlier. There were significantly more counties exceeding thresholds in 2010-2040 compared to 2000-2030 suggesting that adaptation strategies should be employed as soon as possible.Peer reviewe

Interacting environmental stress factors affects targeted metabolomic profiles in stored natural wheat and that inoculated with F. graminearum

Changes in environmental stress impact on secondary metabolite (SM) production profiles. Few studies have examined targeted SM production patterns in relation to interacting environmental conditions in stored cereals. The objectives were to examine the effect of water activity (aw; 0.95–0.90) x temperature (10–25 °C) on SM production on naturally contaminated stored wheat and that inoculated with Fusarium graminearum. Samples were analysed using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) on (a) total number of known SMs, (b) their concentrations and (c) changes under environmental stress. 24 Fusarium metabolites were quantified. Interestingly, statistical differences (ChisSq., p < 0.001) were observed in the number of SMs produced under different sets of interacting environmental conditions. The dominant metabolites in natural stored grain were deoxynivalenol (DON) and nivalenol (NIV) followed by a range of enniatins (A, A1, B, B1), apicidin and DON-3-glucoside at 10 °C. Increasing temperature promoted the biosynthesis of other SMs such as aurofusarin, moniliformin, zearalenone (ZEN) and their derivatives. Natural wheat + F. graminearum inoculation resulted in a significant increase in the number of metabolites produced (ChisSq., p < 0.001). For ZEN and its derivatives, more was produced under cooler storage conditions. Fusarin C was enhanced in contrast to that for the enniatin group. The relative ratios of certain groups of targeted SM changed with environmental stress. Both temperature and aw affected the amounts of metabolites present, especially of DON and ZEN. This study suggests that the dominant SMs produced in stored temperate cereals are the mycotoxins for which legislation exists. However, there are changes in the ratios of key metabolites which could influence the relative contamination with individual compounds. Thus, in the future, under more extreme environmental stresses, different dominant SMs may be formed which could make present legislation out of step with the future contamination which might occur