Effects of temperature, incubation period and substrate on production of fusaproliferin by Fusarium subglutinans ITEM 2404

Influence of H2O2-Induced Oxidative Stress on In Vitro Growth and Moniliformin and Fumonisins Accumulation by Fusarium proliferatum and Fusarium subglutinans

Fusarium proliferatum and Fusarium subglutinans are common pathogens of maize which are known to produce mycotoxins, including moniliformin (MON) and fumonisins (FBs). Fungal secondary metabolism and response to oxidative stress are interlaced, where hydrogen peroxide (H₂O₂) plays a pivotal role in the modulation of mycotoxin production. The objective of this study is to examine the effect of H₂O₂-induced oxidative stress on fungal growth, as well as MON and FBs production, in different isolates of these fungi. When these isolates were cultured in the presence of 1, 2, 5, and 10 mM H₂O₂, the fungal biomass of F. subglutinans isolates showed a strong sensitivity to increasing oxidative conditions (27–58% reduction), whereas F. proliferatum isolates were not affected or even slightly improved (45% increase). H₂O₂ treatment at the lower concentration of 1 mM caused an almost total disappearance of MON and a strong reduction of FBs content in the two fungal species and isolates tested. The catalase activity, surveyed due to its crucial role as an H₂O₂ scavenger, showed no significant changes at 1 mM H₂O₂ treatment, thus indicating a lack of correlation with MON and FB changes. H₂O₂ treatment was also able to reduce MON and FB content in certified maize material, and the same behavior was observed in the presence and absence of these fungi, highlighting a direct effect of H₂O₂ on the stability of these mycotoxins. Taken together, these data provide insights into the role of H₂O₂ which, when increased under stress conditions, could affect the vegetative response and mycotoxin production (and degradation) of these fungi.

Ecophysiology of Fusarium temperatum isolated from maize in Argentina

The effect of water activity (aw = 0.95, 0.98 and 0.995), temperature (15, 25 and 30°C), incubation time (7, 14, 21 and 28 days), and their interactions on growth and moniliformin (MON), beauvericin (BEA), fusaproliferin (FUS) and fumonisin B1 (FB1) production by two strains of Fusarium temperatum isolated from Argentinean maize were determined in vitro on sterile layers of maize grains. The results showed that there was a wide range of conditions for growth and mycotoxins production by F. temperatum. Both strains were found to grow faster with increasing aw and at 30°C. In relation to mycotoxin production, the two strains produced more FUS than the other mycotoxins regardless of aw or temperature evaluated (maximum = 50,000 μg g(-1)). For FUS, MON and BEA, the maximum levels were observed at 0.98 aw and 30°C (50,000, 5000 and 2000 μg g(-1) respectively). The lowest levels for these three mycotoxins were detected at 15°C and 0.95 aw (1700 and 100 μg g(-1) for FUS and MON respectively), and at 0.98 aw (400 μg g(-1) for BEA). The maximum levels of FB1 were produced at 15°C and 0.98 aw (1000 μg g(-1)). At all aw and temperatures combinations evaluated there was an increase in toxin concentrations with time incubation. The maximum levels were detected at 21 days. Statistical analyses of aw, temperature, incubation time, and the two- and three-way interactions between them showed significant effects on mycotoxins production by F. temperatum. For its versatility on growth and mycotoxin production, F. temperatum represents a toxicological risk for maize in the field and also during grain storage.

Climate change impacts on mycotoxin risks in US maize

To ensure future food security, it is crucial to understand how potential climate change scenarios will affect agriculture. One key area of interest is how climatic factors, both in the near- and the long-term future, could affect fungal infection of crops and mycotoxin production by these fungi. The objective of this paper is to review the potential impact of climate change on three important mycotoxins that contaminate maize in the United States, and to highlight key research questions and approaches for understanding this impact. Recent climate change analyses that pertain to agriculture and in particular to mycotoxigenic fungi are discussed, with respect to the climatic factors – temperature and relative humidity – at which they thrive and cause severe damage. Additionally, we discuss how climate change will likely alter the life cycles and geographic distribution of insects that are known to facilitate fungal infection of crops.

Overview of analytical methods for beauvericin and fusaproliferin in food matrices

In recent years consumers and the scientific community have become increasingly interested in food safety, making it a major focus among the objectives of the international institutions responsible for food safety monitoring, e.g. the European Union or the EFSA. Aspects attracting much attention are the colonization of food by microscopic fungi which, under aerobic conditions, produce toxic secondary metabolites known as mycotoxins, and the accumulation of these toxins in the food chain. Numerous studies of surveillance, detoxification, prevention, and toxicological aspects reported in the literature mostly concentrate on major mycotoxins such as aflatoxins, ochratoxin A, trichothecenes, and fumonisins; studies on toxic secondary metabolites of mycotoxins are less common or are only just beginning. Among the molecules of interest, the family of beauvericin and fusaproliferin is certainly the most interesting. The objective of this review is to summarize reported data and the methods used to extract and quantify beauvericin and fusaproliferin in food matrices.

Purification of fusaproliferin from cultures of Fusarium subglutinans by preparative high-performance liquid chromatography

Thirty-six Fusarium strains were grown on cracked yellow corn and evaluated for optimum fusaproliferin production, with Fusarium subglutinans E-1583 producing the highest levels (1600 microg/g). Three solvent systems were tested for extracting fusaproliferin from the cultures of F. subglutinans E-1583. Methanol gave the highest fusaproliferin recovery, followed by methanol/1% aqueous NaCl (55:45, v/v) and acetonitrile/methanol/H(2)O (16:3:1, v/v/v). Hexane partitioning was effective in removing many impurities from the crude fusaproliferin extracts prior to the liquid chromatography step. Fusaproliferin samples were further purified by high-performance liquid chromatography (HPLC) with a C18 preparatory column using a mobile phase of acetonitrile/H(2)O (80:20, v/v). The purity of the fusaproliferin was verified by analytical HPLC, GC/MS, (1)H NMR spectroscopy, and electrospray ionization (ESI) MS. The isolated fusaproliferin was shown to be free of impurities and can be used as a standard for routine analysis. Fusaproliferin was shown to be temperature-sensitive when samples were stored at room temperature (20-24 degrees C) for more than several days. After 30 days at 4 degrees C, approximately 8% of the fusaproliferin had been transformed to deacetyl-fusaproliferin; however, samples stored at -20 degrees C for 1 year contained only trace amounts of the deacetylated form.