Potencial de toxicidade de microfungos isolados de rações para peixes fabricadas no estado do Amazonas

Abstract

Microfungi in animal feed can produce metabolites detrimental to productivity, especially in intensive farming systems. Deleterious effects can reach the final consumer – the man. In this study, samples of extruded fish feed produced in Amazonas, Brazil (factories F1 and F2, n = 15 each) had the mycobiota identified and quantified. Some isolates (n=29) were characterized for toxicity against Artemia salina; additionally pH and moisture were compared at favorable conditions to fungal development. For isolation and quantification, decimal dilutions were inoculated on rose bengal chloramphenicol agar, in triplicate, incubated at 25 °C / 7 days. Obtained cfu/g (F1=1.45x102, F2=3.77x10) below the threshold for animal feed (105 cfu/g). Humidity (F1=8.82%, F2=8.21%) and pH (F1=6.64, F2=6.66) were suitable to fungi growth, especially xerophilic. 881 colonies were isolated (F1=85.5%, F2=14.5%) and 15 species identified, with a higher prevalence of Penicillium implicatum (F1=22.5%, F2=4.0%), Penicillium janczewskii (F1=22.4%, F2=4.1%) and Penicillium melinii (F1=21.9%, F2=4.0%). Crude aqueous extracts were submitted to two types of toxicity bioassay - with presence (DPFP) and absence (DPFA) paper filter disc - which confirmed the Artemia salina sensitivity to myco-metabolites. Altought mixed results in some isolates of Absidia cylindrospora and P. janczewskii (toxic when DPFP, highly toxic when DPFA). Nevertheless, statistically, bioassays aqueous extracts are not influenced by paper disk filter presence. Despite the good quality of extruded feed, these microorganisms occurrence is worrying due severe bioactivity of extrolits from isolates and relative metabolites stability to food processing, meaning risks to productivity, animal health and consumers of farmed fish.