Fungi and mycotoxins in silage: an overview Alonso, V.A.; Pereyra, C.M.; Keller, L.A.M. ...
Journal of applied microbiology,
September 2013, Letnik:
115, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Summary
The present revision shows the early and current knowledge in the field of silage fungi and mycotoxins explaining the relevance of fungi and mycotoxins in silage. The problem does not end in ...animal disease or production losses as mycotoxins in feed can lead to the presence of their metabolic products in dairy products, which will be eventually affecting human health, mainly infants. Silage is green forage preserved by lactic fermentation under anaerobic conditions. This ecosystem maintains its quality and nutritional value depending on interactions among physical, chemical and biological agents. Forages used for ensilage are naturally in contact with yeasts and filamentous fungi, and the contamination often occurs in the field and can also occur during harvesting, transport, storage. Moreover, postharvest poor management can lead to a rapid spoilage. Studies on fungal contamination of dairy cattle feed have shown how corn silage influences the contamination degree of feed supplied to livestock. Increasing knowledge in this area will help elucidate the influence that this microbiota exerts on production and/or degradation of mycotoxins present in silage. Some of these fungi, although opportunist pathogens, are relevant epidemiologically and represent a high risk of contamination to farm workers who handle them improperly.
Aims: To examine Saccharomyces cerevisae strains with previously reported beneficial properties and aflatoxin B1 binding capacity, for their ability to remove ochratoxin A (OTA) and zearalenone ...(ZEA) and to study the relation between cell wall thickness and detoxificant ability of yeast strains.
Methods and Results: A mycotoxin binding assay at different toxin concentrations and the effect of gastrointestinal conditions on mycotoxin binding were evaluated. Ultrastructural studies of yeast cells were carried out with transmission electronic microscopy. All tested strains were capable of removing OTA and ZEA. Saccharomyces cerevisiae RC012 and RC016 showed the highest OTA removal percentage, whereas RC009 and RC012 strains showed the highest ZEA removal percentages. The cell diameter/cell wall thickness relation showed a correlation between cell wall amount and mycotoxin removal ability. After exposure to gastrointestinal conditions, a significant increase in mycotoxin binding was observed.
Conclusions: All tested Saccharomyces cerevisiae strains were able to remove OTA and ZEA, and physical adsorption would be the main mechanism involved in ochratoxin A and ZEA removal. Gastrointestinal conditions would enhance adsorption and not decrease mycotoxin–adsorbent interactions.
Significance and Impact of the Study: Live strains with mycotoxin binding ability and beneficial properties are potential probiotics that could be included in animal feed. Previous and present results suggest that the RC008 and RC016 strains are very promising candidates for functional feed product development.
Aflatoxins (AF) are a major problem in broiler production and are significant economic and public health burdens worldwide. A commercial sodium bentonite (Na-B) adsorbent was used to prevent the ...effect of AF 50 μg of aflatoxin B₁ (AFB₁)/kg of feed in broiler productivity, biochemical parameters, macroscopic and microscopic liver changes, and AFB₁ liver residues. The influence of Na-B (0.3%) and monensin (MON, 100 mg/kg), alone or in combination, was investigated in depth. The dietary treatments were as follows: treatment (T) 1: basal diet (B); T2: B + MON; T3: B + Na-B; T4: B + Na-B + MON; T5: B + AFB₁; T6: B + AFB₁ + Na-B + MON; T7: B + AFB₁ + MON; T8: B + AFB₁ + Na-B. Birds were fed dietary treatments for 28 d (d 18 to 46). No significant differences (P < 0.05) were observed among treatments with respect to broiler performance, biochemical parameters, or relative liver weights. With the exception of T8, all livers showed histopathological alterations, with accumulation of fat vacuoles. The normal appearance of livers from T8 showed the protective effect of Na-B against aflatoxicosis. The residual AFB₁ levels in livers from T5 to T8 ranged from 0.2 to 1.0 ng/g and were higher in livers from T6 (P < 0.05). Results of this study indicate a competition between AFB₁ and MON for adsorption sites on Na-B when feed contains low levels of the toxin, indicating a nonselective adsorption capacity of this particular Na-B. In addition, significant levels of AFB₁ in livers indicate that this determination is an important technique not only for diagnosis of aflatoxicosis in broilers, but also for quality control of avian products.
Aim
This study evaluated the binding capacity of aflatoxin B1 (AFB1) by two Enterococcus faecium strains (MF4 and GJ40) isolated from faeces from healthy dogs.
Materials and Methods
The binding assay ...was performed using 50 and 100 ppb of AFB1 analysing the effects of the viability, incubation time and pH on AFB1 binding. Binding stability was determined by washing three times the bacteria‐AFB1 complexes with phosphate buffer saline.
Results
Both GJ40 and MF4 strains have the ability to remove AFB1 from aqueous solution. Viable cells were slightly more effective in AFB1 binding than nonviable ones for both strains. Enterococcus faeciumGJ40 removes 24–27% and 17–24%, and Ent. faeciumMF4 removes 36–42% and 27–32% of AFB1 (50 and 100 ppb, respectively) throughout a 48 h incubation period. In general, the removal of AFB1 was highest at pH 7·00 for both strains. The stability of the bacteria‐AFB1 complex formed was found to be high (up to 50% of AFB1 remained bounded in bacterial cell after three washes with phosphate buffered saline).
Conclusion
The Ent. faecium strains assayed are capable of removing AFB1 under different conditions in vitro.
Significance and Impact of the Study
This is the first AFB1 binding assay performed with Ent. faecium strains isolated from dog faeces, being an interesting strategy for AFB1 decontamination of pet food.
Aims
To isolate and characterize native yeast strains from broilers’ environment as feedstuff, faeces and gut, and to evaluate their binding capacity for aflatoxin B1 (AFB1).
Methods and Results
A ...total of nine yeast strains were isolated: three from feedstuff identified as Pichia kudriavzevii (2) and Clavispora lusitaniae (1), two from gut identified as Candida tropicalis and four from faeces identified as Cl. lusitaniae (3) and Cyberlindnera fabianii (1). AFB1 binding percentages varied among yeast strains and with AFB1 concentrations. To carry out adsorption studies, one strain from each genus and each origin was selected as follows: Cl. lusitaniae and P. kudriavzevii from feedstuff, Cl. lusitaniae and Cy. fabianii from faeces and Ca. tropicalis from gut. The most appropriate concentrations for cells and toxin were 107 cells per ml and 100 ng ml−1 of AFB1 respectively. All the tested yeast strains showed similar adsorption capacities independently of the origin. The adsorption isotherm studies in all yeasts assayed showed behaviour of L type or Langmuir and a varied affinity for the toxin. The stability of the AFB1–yeast complex demonstrated the irreversibility of the binding process.
Conclusion
Yeast strains tested in this study constitute potential AFB1 adsorbents and they possess the advantage to be native from the avian environment.
Significance and Impact of the Study
This study makes a contribution to using native yeasts from broilers’ environment for controlling chronic aflatoxicosis in avian production.
Aim
To evaluate the ability of probiotic Saccharomyces cerevisiae RC016 strain to reduce fumonisin B1 (FB1) in vitro and to optimize the culture conditions for the growth of the yeast employing ...surface response methodology.
Methods and Results
Using Plackett–Burman screening designs (PBSD) and central composite designs (CCD), an optimized culture medium containing (g l−1) fermentable sugars provided by sugar cane molasses (CMs), yeast extract (YE) and (NH4)2HPO4 (DAP) was formulated. The S. cerevisiae RC016 strain showed the greatest binding at all assayed FB1 concentration. The CMs, YE, DAP concentrations and incubation time influenced significantly the biomass of S. cerevisiae RC016.
Conclusion
A combination of CMs 17%; YE 4·61 g l−1 and incubation time 60 h was optimum for maximum biomass of S. cerevisiae RC016.
Significance and Impact of the Study
The importance of this work lies in the search for live strains with both probiotic and fumonisin B1 decontamination properties that could be sustainably produced in a medium just containing cheap carbon, nitrogen and phosphorus sources and would be included in a novel product to animal feed.
Aims: The aims of this work were to identify the mycoflora and to evaluate the natural occurrence of OA in dried vine fruits. Likewise, the capacity to produce OA by Aspergillus section Nigri was ...studied.
Materials and Methods: Fifty samples of dried vine fruits were obtained from Mendoza and San Juan provinces. The surface disinfection method was used for mycoflora determination using the medium dichloran 18% glycerol agar (DG18) and dichloran Rose Bengal chloramphenicol agar (DRBC).
Results: Statistical analysis demonstrated that the species A. niger var. niger and Aspergillus niger var. awamori were isolated in higher frequency from black dried vine fruits from DRBC and DG18 media (P < 0·01). OA was found in 74% of the dried vine fruits samples. Sixty‐two strains (28%) of Aspergillus section Nigri, were OA producers. In the species A. carbonarius the highest percentages of ochratoxigenic strains were detected (82·6%).
Conclusions: The presence of ochratoxigenic strains of Nigri section in dried vine fruits suggests that they may be an important source of OA in this substrate. Dried vine fruits can also be an important source of OA people who consume large amounts.
Significance and Impact of the Study: The dried vine fruits contamination with Aspergillus section Nigri and OA was significant.
Aim: To determine fungal genera, Aspergillus and Fusarium species and aflatoxin B1 (AFB1), zearalenone (ZEA), deoxynivalenol (DON), fumonisin B1 (FB1) contamination from pre‐ and postfermented corn ...silage produced in the most important region of Argentina where silage practice is developed.
Methods and Results: Sampling of corn silos was performed manually through silos in transects at three levels: upper, middle and low sections. AFB1 and FB1 were quantified by high‐performance liquid chromatography, zearalenone by enzyme‐linked immunosorbent assay and DON by gas chromatography. Over 90% of the samples showed counts higher than 1 × 104 CFU g−1. Aspergillus flavus and Fusarium verticillioides were the prevalent species. Some tested samples were contaminated with AFB1, ZEA, DON and FB1.
Conclusions: This study demonstrates the presence of fungi and AFB1, ZEA, DON and FB1 contamination in corn silage in Argentina.
Significance and Impact of the Study: This manuscript makes a contribution to the knowledge of mycotoxins in Argentinean silage in particular because the environmental conditions in this country differ from those of most reports. The comparison of pre‐ and postfermentation silage is also outstanding. Therefore, information on fungi and mycotoxins present in silage – an increasingly popular commodity – is useful to estimate potential risk for animal and human health.
The effect of Saccharomyces cerevisiae RC008 and RC016 strains, previously selected based on their aflatoxin B1 mycotoxin binding ability and beneficial properties, against Aspergillus carbonarius ...and Fusarium graminearum under different interacting environmental conditions was evaluated. In vitro studies on the lag phase, growth rate and ochratoxin A/zearalenone and DON production were carried out under different regimens of aw (0.95 and 0.99); pH (4 and 6); temperature (25 and 37°C) and oxygen availability (normal and reduced). Both yeast strains showed antagonistic activity and decreasing growth rate compared to the control. In general, the RC016 strain showed the greatest inhibitory activity. Except at the interacting condition 0.95 aW, normal oxygen availability and 37°C, at both pH values, A. carbonarius and F. graminearum were able to produce large amounts of mycotoxins in vitro. In general, a significant decrease in levels of mycotoxins in comparison with the control was observed.
S. cerevisiae RC008 and RC016 could be considered as effective agents to reduce growth and OTA, ZEA and DON production at different interacting environmental conditions, related to those found in stored feedstuff. The beneficial and biocontrol properties of these strains are important in their use as novel additives for the control of mycotoxigenic fungi in stored feedstuffs.
Aims: To evaluate mycobiota and aflatoxins B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2) and fumonisin B1 (FB1) contamination in different malted barley types and brands and brewer’s grain collected ...from a major Argentinean brewery. Methods and Results: Total fungal counts were performed using the plate count method. Aflatoxin B1, AFB2, AFG1, AFG2 and Zearalenone (ZEA) analyses were performed by thin‐layer chromatography (TLC). Fumonisin B1 was determined by HPLC. Eighty‐three percentage of the malted barley (100% M1, 50% M2 and 100% M3) and 61% of brewer’s grain samples had a count >1 × 104 CFU g−1. Yeasts were isolated from all malt and brewer’s grain samples. Genera containing some of the most important mycotoxin producer species –Fusarium ssp., Aspergillus ssp., Penicillium ssp. and Alternaria ssp. – were isolated from the analysed samples, along with other environmental saprophytic fungi such as Geotrichum ssp., Mucorales and Cladosporium ssp. All samples were contaminated with 104–145 μg kg−1 FB1. Eighteen per cent of brewer’s grain samples were contaminated with 19–44·52 μg kg−1 AFB1. Aflatoxin B2, AFG1, AFG2 and ZEA were not detected in any of the analysed samples. Conclusions: Fungal and mycotoxin contamination in malt and brewer’s grain is an actual risk for animal and human health. Significance and Impact of the Study: This study may be useful for assessing the risk of mycotoxins in Argentinean beers and especially in animal feeds.
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