Saccharomyces cerevisiae From Silage inhibit Aspergillus parasiticus Growth And AFB1 Production

ARMANDO, MR; DOGI, CA; DALCERO, AM; CAVAGLIERI, LR

Mendoza

Congreso; International Society of Mycotoxicology; 2011

Aflatoxin contamination of crops is a worldwide problem that compromises the safety of food and feed and devastates agricultural economies. Many strategies, including biological control, are being investigated to manage, reduce, and ultimately eliminate aflatoxin contamination of crops. Microbial biocontrol agents have shown to be great potential as an alternative to synthetic pesticides and fungicides. Forage stored in silo such as maize silage is subjected to a wide range of different environmental conditions. Poor storage conditions can lead to undesirable mold contamination, mycotoxin production and the reduction of nutritional value. Yeasts are prevalent microorganisms in feed ecosystems and they have been assigned as deteriorating agents in this substrate. The aim of this work was to study the effect of Saccharomyces cerevisiae RC008 and RC016, previously selected based on their aflatoxin B1 (AFB1) binding ability and antagonistic substances production, against Aspergillus parasiticus under different interacting environmental conditions. Studies on the lag phase, growth rate and aflatoxin B1 production were carried out in vitro under different regimes of aw (0.95 and 0.99); pH (4 and 6); temperature (25 and 37°C) and oxygen availability (normal and reduced), simulating the environmental conditions of silage. The effect of supernatant yeast culture on A. parasiticus growth and AFB1 production was also evaluated. At pH 4, some level of fungal growth inhibition was observed by yeast interaction, especially with RC008 strain. Both yeast strains showed great antagonistic activity at pH 4, decreasing growth rate compared to the control. The RC008 strain showed the greatest inhibitory activity at all assayed conditions. Aspergillus parasiticus was able to in vitro produce large amounts of AFB1. A great decrease of AFB1 levels in comparison with the control were observed with yeast interaction. Differences between control and treatment values ranged between 130 and 5400 ng/ml. The yeast culture supernatant-A. parasiticus interaction showed that the presence of yeast cells are necesary to growth inhibition, but some metabolite released after yeast growth are able to inhibit the AFB1 production at pH 6. The present work indicates a possible beneficial role that S. cerevisiae plays in the silage ecosystem, since the assayed strains could prevent AFB1 contamination in this substrate. The data show that S. cerevisiae RC008 and RC016 strains could be considered as effective agents to reduce growth and AFB1 production by aflatoxin producer strains. The information obtained is of relevance for controlling growth and AFB1 production at different interacting environmental conditions, related to that found in stored feedstuff.