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Effects of different substrates and oils on aflatoxin B1 production by Aspergillus parasiticus

Ma Huihui,Zhang Niya,Sun Lvhui,Qi Desheng

Aflatoxin contamination levels vary from crop to crop, suggesting that it is of great significance to explore the effects of different substrates on aflatoxins production. In this study, the effects of corn, wheat, peanut, and soybean on aflatoxin B 1 (AFB 1 ) production by Aspergillus parasiticus were investigated, and the effects of corn germ, wheat germ, soybean, and peanut oils on the production of AFB 1 by A . parasiticus in the corresponding defatted substrates were evaluated at the rates of 2, 5, 10, and 15 g/100 g of substrate. The effects of the combinations of different oils with different defatted substrates on the accumulation of AFB 1 by A . parasiticus were also studied. AFB 1 concentration was determined by HPLC. The results indicated that high-lipid substrates of soybean and peanut had significantly higher AFB 1 production than low-fat substrates of wheat and corn throughout the entire incubation period (15 days) in both autoclaved and non-autoclaved grains. Corn germ, wheat germ, soybean, and peanut oils with different doses could effectively stimulate AFB 1 accumulation, and AFB 1 production was determined by the oil content of the substrates. Our results suggest that the oil content of substrates is one of the factors affecting AFB 1 production by A . parasiticus and that the composition and content of the substrates may also play a role.

Investigations on the Antifungal Effect of Nerol against Aspergillus flavus Causing Food Spoilage

Jun Tian,Xiaobin Zeng,Hong Zeng,Zhaozhong Feng,Xiangmin Miao,Xue Peng

The antifungal efficacy of nerol (NEL) has been proved against Aspergillus flavus by using in vitro and in vivo tests. The mycelial growth of A. flavus was completely inhibited at concentrations of 0.8 μL/mL and 0.1 μL/mL NEL in the air at contact and vapor conditions, respectively. The NEL also had an evident inhibitory effect on spore germination in A. flavus along with NEL concentration as well as time-dependent kinetic inhibition. The NEL presented noticeable inhibition on dry mycelium weight and synthesis of aflatoxin B1 (AFB1) by A. flavus, totally restraining AFB1 production at 0.6 μL/mL. In real food system, the efficacy of the NEL on resistance to decay development in cherry tomatoes was investigated in vivo by exposing inoculated and control fruit groups to NEL vapor at different concentration. NEL vapors at 0.1 μL/mL air concentration significantly reduced artificially contaminated A. flavus and a broad spectrum of fungal microbiota. Results obtained from presented study showed that the NEL had a great antifungal activity and could be considered as a benefit and safe tool to control food spoilage.

Inhibition of Aspergillus flavus growth and aflatoxins production on peanuts over α-Fe2O3 nanorods under sunlight irradiation

Di Sun,Jin Mao,Zhijian Wang,Hui Li,Liangxiao Zhang,Wen Zhang,Qi Zhang,Peiwu Li

Peanut is an important resource of edible oil and digestible protein in daily life, which is rich in the nutriments and antioxidants such as vitamins, minerals and polyphenols. However, peanut is susceptible to the contamination of Aspergillus flavus ( A. flavus ), which can produce highly carcinogenic toxins that brings serious threats to human health and food safety. Exploring green and effective methods to control A. flavus is meaningful. Herein, a green and economical way to control A. flavus on peanuts was demonstrated. It was found that the growth of A. flavus hyphae and germination of its spores could be inhibited in the presence of α-Fe 2 O 3 nanorods under sunlight irradiation according to the agar diffusion method , flat colony counting method and fluorescence-based live/dead test. The diameter of inhibition zone was 22.3 ± 0.2 mm and the inhibition rate of spores germination was about 60 ± 5%, when the concentration of α-Fe 2 O 3 was 10 mg/mL for 7 h sunlight irradiation. Most important, α-Fe 2 O 3 showed the photocatalytic inhibition of A. flavus on peanuts under sunlight irradiation with the inhibition rate of about 90 ± 5%, and the production of aflatoxin B 1 and aflatoxin B 2 were reduced by 90 ± 2% and 70 ± 3%, respectively. By comparing the fat contents, protein contents, acid value, peroxide value and antioxidative compositions of peanuts, it was found that there was no obvious effect on the quality of peanuts after inhibition treatment. The findings provide a green, safe and economical strategy to control A. flavus on peanuts, which may be as a promising way to be used in food and agro-food preservation.

PP2C phosphatases Ptc1 and Ptc2 dephosphorylate PGK1 to regulate autophagy and aflatoxin synthesis in the pathogenic fungus Aspergillus flavus

Zhuo Zhu,Mingkun Yang,Guang Yang,Bei Zhang,Xiaohong Cao,Jun Yuan,Feng Ge,Shihua Wang

Inhibition Mechanism of Cinnamomum burmannii Leaf Essential Oil Against Aspergillus flavus and Aflatoxins

Huanyan Liang,Feifei Lv,Mengting Xian,Chenghua Luo,Lei Zhang,Meihua Yang,Qian Li,Xiangsheng Zhao

This investigation evaluates the comparative efficacy ofCinnamomum burmanniileaf essential oil (YXYO) and its main active ingredients as a novel preservative to protect stored food commodities from fungal infestations, aflatoxin B1(AFB1) contamination caused byAspergillus flavus. Morphological observations utilizing SEM and TEM revealed significant alterations in treated samples, alongside a decrease in ergosterol content and a dose-dependent disruption of the antioxidant system and energy system. Transcriptomic analysis suggested that differentially expressed genes were predominantly associated with spore growth, the cell wall, the cell membrane, oxidative stress, energy metabolism, and aflatoxin biosynthesis. Solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS) identified ten active ingredients in YXYO, including borneol,α-terpineol, terpinen-4-ol, etc. Moreover, an effective inhibition ofA. flavusinfection in peanuts was observed with the application of 30 μL/disc of YXYO and a blend of its active compounds.

Screening a Strain of Aspergillus niger and Optimization of Fermentation Conditions for Degradation of Aflatoxin B1

Wei Zhang,Beibei Xue,Mengmeng Li,Yang Mu,Zhihui Chen,Jianping Li,Anshan Shan

Aflatoxin B1, a type of highly toxic mycotoxin produced by some species belonging to theAspergillusgenus, such asAspergillus flavusandAspergillus parasiticus, is widely distributed in feed matrices. Here, coumarin was used as the sole carbon source to screen microorganism strains that were isolated from types of feed ingredients. Only one isolate (ND-1) was able to degrade aflatoxin B1after screening. ND-1 isolate, identified as a strain ofAspergillus nigerusing phylogenetic analysis on the basis of 18S rDNA, could remove 26.3% of aflatoxin B1after 48 h of fermentation in nutrient broth (NB). Optimization of fermentation conditions for aflatoxin B1degradation by selectedAspergillus nigerwas also performed. These results showed that 58.2% of aflatoxin B1was degraded after 24 h of culture under the optimal fermentation conditions. The aflatoxin B1degradation activity ofAspergillus nigersupernatant was significantly stronger than cells and cell extracts. Furthermore, effects of temperature, heat treatment, pH, and metal ions on aflatoxin B1degradation by the supernatant were examined. Results indicated that aflatoxin B1degradation ofAspergillus nigeris enzymatic and this process occurs in the extracellular environment.Keywords:Aspergillus niger;coumarin;aflatoxin B1;degradation

Study on the Dynamic Changes in Fungal Communities During the Storage of Polygalae Radix and the Antifungal Effects of Peppermint Essential Oil

Hui Zhang,Yuying Su,Xinnan Wang,Ying Ren,Jinfeng Li,Jianping Han

Polygalae Radix, a traditional Chinese medicine for insomnia and memory disorders, is highly susceptible to fungal contamination and mycotoxin production (especially byAspergillus flavus) during storage, compromising its safety and efficacy. Therefore, in this study, high-throughput sequencing was employed to evaluate the dynamic changes in fungal communities during the storage of Polygalae Radix and to analyze common mycotoxin-producing genera. Furthermore, the inhibitory effects of peppermint essential oil (PEO) onA. flavuswere assessed through fumigation treatments, combined with colony counting and quantification of aflatoxins. Results showed the following: (1) Storage for 1–3 months significantly altered the fungal structure, promoting saprophytic and pathogenic fungi (e.g.,Wallemia,Paraphoma,Didymella,Cladosporium…) and increasing the relative abundance of mycotoxin producers likePenicillium,Aspergillus, andFusarium(notably,Penicilliumincreased from 0.28–2.33% to 5.39–80.43%). Additionally,A. flavus, capable of producing aflatoxins, was detected in samples stored for two months (RM2). (2) Antifungal tests demonstrated that PEO significantly inhibited the common fungi in Polygalae Radix. At 10 μL/g, it suppressed fungal growth and significantly reduced aflatoxin B1(AFB1) and total aflatoxins (AFT, including AFB1, AFB2, AFG1, and AFG2) levels (p< 0.05). At 10 μL/g, AFB1and AFT were reduced to undetectable levels. PEO can serve as a green and effective protective strategy to inhibitA. flavusduring the storage of Polygalae Radix and control aflatoxin contamination.

Adsorption of aflatoxins and ochratoxins in edible vegetable oils with dopamine-coated magnetic multi-walled carbon nanotubes

Hongwen Xu,Jiadi Sun,Haiming Wang,Yinzhi Zhang,Xiulan Sun

A new, green, and cost-effective magnetic solid-phase extraction of aflatoxins and ochratoxins from edible vegetable oils samples was developed using polydopamine-coated magnetic multi-walled carbon nanotubes (PDA@Fe 3 O 4 -MWCNTs) as the absorbent. PDA@Fe 3 O 4 -MWCNTs nanomaterials were prepared by chemical co-precipitation and in situ oxidation and self-polymerization of dopamine and was characterized. Factors affecting MSPE and the adsorption behavior of the adsorbent to mycotoxins were studied, and the optimal extraction conditions of MSPE and the complexity of the adsorption process were determined. Based on this, the magnetic solid-phase extraction-high-performance liquid chromatography-fluorescence detection method (MSPE-HPLC-FLD) was established for determining six mycotoxins [aflatoxin B 1 (AFB 1 ), AFB 2 , AFG 1 , and AFG 2 , and ochratoxin A (OTA) and OTB)] in vegetable oils. The recovery was 70.15%~89.25%, and RSD was ≤6.4%. PDA@Fe 3 O 4 -MWCNTs showed a high affinity toward aflatoxins and ochratoxins, allowing selective extraction and quantification of aflatoxins and ochratoxins from complex sample matrices.

Electrochemical analysis of specific catalase activity during development of Aspergillus flavus and its correlation with aflatoxin B1 production

Yanjing Yun,Zhisong Lu,Jing Yang,Taotao Liang,Gang Xiao,Yan Qiao,Yang Liu

Aflatoxin B 1 (AFB 1 ) contamination causes huge economic losses. To explore the correlation between catalase (CAT) and AFB 1 production during fungal development, we fabricated an electrochemical CAT-activity sensor by measuring residual H 2 O 2 after enzymatic degradation. The sensor made by palladium nanoparticles/carbonized bacterial cellulose nanocomposites exhibits a linear range over 0.5–3.5 U/mL and a detection limit of 0.434 U/mL. Both dry weight and CAT activity of mycelia continuously increase. But, the latter shows a greater increase than the former after three days. Specific CAT activity in crude enzyme extract of A. flavus was quantified. It maintains at ~25.00 U/mg for 3 days and enhances to 28.91 and 45.30 U/mg, respectively, on days 4 and 5. AFB 1 production follows the same trend. On days 4 and 5, AFB 1 concentration reaches 201.35 and 767.9 ng/mL, respectively. The positive correlation between specific CAT activity and AFB 1 production suggests that CAT is involved in AFB 1 biosynthesis.

A novel sample pretreatment of nanofiber-packed solid-phase extraction of aflatoxin B1, B2, G1 and G2 in foods and simultaneous determination with HPLC

Yunzheng Wang,Lanling Chu,Jiansong Qu,Bo Ding,Xuejun Kang

A novel analytical method based on nanofiber-packed solid-phase extraction (PFSPE) combined with HPLC-FLD has been successfully developed and applied to determine aflatoxin B1, B2, G1, G2 in foods. In order to effectively adsorb analytes from complex food matrices, four types of nanofibers based on skeleton of polystyrene–polyvinyl pyrrolidone were prepared by electrospinning and applied as adsorbent to home-made solid-phase extraction device. The effects of type of nanofibers, pH of sample, type and concentration of salt ion, type of activation solvent, type and volume of eluent, amount of nanofibers, and extraction time on the adsorption/desorption were investigated and optimized. Under optimal conditions, the method showed satisfactory linear relationship, with limits of detection (LODs) of 0.07–0.17 ng g −1 , intra-day and inter-day RSDs for spiked samples of 1.3–8.0 % and 1.9–5.8 %, and absolute recoveries in the range of 60.1–98.4 %. The results presented the great potential to be utilized to determine AFs in foodstuffs.

Hairpin DNA assisted dual-ratiometric electrochemical aptasensor with high reliability and anti-interference ability for simultaneous detection of aflatoxin B1 and ochratoxin A

Chengxi Zhu,Dong Liu,Yuye Li,Shuai Ma,Meng Wang,Tianyan You

The simultaneous detection of multiple mycotoxins in grains is significant due to the enhanced toxicity induced by their synergistic effects . In this work, a dual-ratiometric electrochemical aptasensing strategy for the simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA) was developed. Here, an anthraquinone-2-carboxylic acid (AQ)-labelled complementary DNA (cDNA) was used to provide separate and specific binding sites to assemble the ferrocene-labelled AFB1 aptamer (Fc-Apt1) and methylene blue-labelled OTA aptamer (MB-Apt2). The target-induced current ratios of I Fc /I AQ and I MB /I AQ were then used to quantitatively relate to AFB1 and OTA, respectively. Following this principle, two types of aptasensors involving the hairpin DNA (hDNA) and linear single-stranded DNA (ssDNA) as the cDNA were fabricated for performance comparisons. The results revealed that hairpin DNA with a rigid 2D structure can greatly improve the assembly and recognition efficiency of the sensing interface, which makes the hDNA-based aptasensor possess high sensitivity, reliability and anti-interference ability. The hDNA-based aptasensor exhibited a detection range of 10-3000 pg mL −1 for AFB1 and 30-10000 pg mL −1 for OTA, respectively, with no observable cross-reactivity. Furthermore, the aptasensor was applied to analyze corn and wheat samples, and the reliability was validated by HPLC-MS/MS. Our work has presented a novel way for fabricating a high-performance aptasensor for simultaneous detection of multiple mycotoxins .

Effect of sulfur dioxide and ethanol concentration on fungal profile and ochratoxin a production by Aspergillus carbonarius during wine making

Chunmei Jiang,Junling Shi,Xianqing Chen,Yanlin Liu

Fungal profiles and ochratoxin A (OTA) accumulation during wine making were investigated using five different wine grape cultivars, Cabernet Sauvignon, Pinot Noir, Merlot, Syrah and Petit Verdot and the intrinsic influences caused by sulfur dioxide, ethanol and combine effect of ethanol and reducing sugar were analyzed using Cabernet Sauvignon and inoculation of Aspergillus carbonarius . Aspergillus spp. and Penicillium spp. were found as the major fungi in all winemaking processes and were highly correlated with OTA accumulation in wine. Most fungi died and OTA production decreased after 48 h of alcoholic fermentation , being consistent with the period when ethanol accumulation increased. The addition of SO 2 significantly inhibited the growth and OTA production of A. carbonarius with complete inhibition at 500 mg/L. When the ethanol concentration in the must increased to the range of 2–4%, growth and OTA production of A. carbonarius were significantly inhibited. Reducing sugar concentration had no significant effect on the growth and OTA production of A. carbonarius within the levels changing during the winemaking. Therefore, the increase of ethanol concentration played an important role in causing the decrease of fungal contamination and OTA accumulation during winemaking.