Taxonomic Characterization and Secondary Metabolite Profiling of Aspergillus Section Aspergillus Contaminating Feeds and Feedstuffs

Abstract

Xerophilic fungal species of the genus Aspergillus are economically highly relevant due to their ability to grow on low water activity substrates causing spoilage of stored goods and animal feeds. These fungi can synthesize a variety of secondary metabolites, many of which show animal toxicity, creating a health risk for food production animals and to humans as final consumers, respectively. Animal feeds used for rabbit, chinchilla and rainbow trout production in Argentina were analysed for the presence of xerophilic Aspergillus section Aspergillus species. High isolation frequencies (>60%) were detected in all the studied rabbit and chinchilla feeds, while the rainbow trout feeds showed lower fungal charge (25%). These section Aspergillus contaminations comprised predominantly five taxa. Twenty isolates were subjected to taxonomic characterization using both ascospore SEM micromorphology and two independent DNA loci sequencing. The secondary metabolite profiles of the isolates were determined qualitatively by HPLC-MS. All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B. Physcion and preechinulin were detected in a minor proportion of the isolates. This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.

A survey of xerophilic Aspergillus from indoor environment, including descriptions of two new section Aspergillus species producing eurotium-like sexual states

“…Echinulin was first discovered in A. brunneus (= E. echinulatum) by Quilico and Panizzi (1943). It was subsequently detected in many more section Aspergillus species (Ali et al 1989;Almeida et al 2010;Greco et al 2015;Li et al 2008b;Slack et al 2009;Smetanina et al 2007;Vesonder et al 1988) and shown to be toxic to animal cells (Ali et al 1989;Umeda et al 1974), while swine and mice respectively refused feed and water containing echinulin (Vesonder et al 1988). The presence of echinulin in the environment is not well documented however.…”

“…Most notably, compounds from A. chevalieri were shown to be active against Plasmodium falciparum (malaria), Mycobacterium tuberculosis and cancer cell lines (Kanokmedhakul et al 2011), an antitumor compound was reported from A. cristatus (Almeida et al 2010), while many compounds are known to be antioxidants. They also produce mycotoxins, especially echinulin, flavoglaucin and physcion, which are toxic to animals (Ali et al 1989;Bachmann et al 1979;Cole and Cox 1981;Greco et al 2015;Nazar et al 1984;Rabie et al 1964;Semeniuk et al 1971;Slack et al 2009;Vesonder et al 1988), but toxicity has not been reported in humans. These species are not considered significant human pathogens, because most infections are superficial, with few cases of invasive infections known (de Hoog et al 2014).…”

Polyphasic taxonomy of Aspergillus section Aspergillus (formerly Eurotium), and its occurrence in indoor environments and food

“…Aspergillus are generally referred to as osmo-, xero- or halotolerant. They have a world-wide distribution and are common in indoor air, house dust, cereals, food products containing high concentrations of sugar, such as syrups, jams and jellies, salted meat products, semi-dry foods, feeds, leather goods and so on ( Raper and Fennell, 1965 , Blaser, 1975 , Chelkowski et al., 1987 , Pitt and Hocking, 2009 , Samson et al., 2010 , Greco et al., 2015 ). Species in this section are able to initiate growth at minimum moisture levels, thus establishing bridgeheads and facilitating the invasion of slightly less xerophilic molds ( Semeniuk et al., 1947 , Raper and Fennell, 1965 , Kozakiewicz, 1989 ).…”

“…Aspergillus cristatus or “Golden Flower Fungus” is used in the production of Fuzhuan brick tea in China ( Wen, 1990 , Qi and Sun, 1990 , Xu et al., 2011 ); Aspergillus pseudoglaucus (= Eurotium repens ) is used as a starter culture in the manufacturing of katsuobushi and fish sauce ( Hayakawa et al., 1993 , Dimici and Wada, 1994 ); A. pseudoglaucus , A. chevalieri and A. montevidensis are frequently isolated from meju (dried fermented soybeans); two newly described species A. cibarius and A. cumulatus are also isolated from meju or meju fermentation related environment ( Hong et al., 2011 , Hong et al., 2012 , Kim et al., 2014 ). Aspergillus chevalieri , A. cristatus , A. glaucus , A. montevidensis , A. proliferans , A. pseudoglaucus and A. ruber have been reported from feedstuffs very often ( Pitt and Hocking, 2009 , Samson et al., 2010 , Greco et al., 2015 ). These species have also been reported from other habitats and substrates.…”

Response to Pitt & Taylor 2016: Conservation ofAspergilluswithA. nigeras the conserved type is unnecessary and potentially disruptive

“…(2016) in their studies on molecular screening of xerophilic Aspergillus strains; (iii) Schulthess & al. (2014) for their identifications of clinical moulds; and (iv) Greco & al. (2015) in their characterization of species on feeds and feedstuff.…”