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The effect of Saccharomyces cerevisiae RC008 and RC016, previously selected based on their aflatoxin B1 binding ability and beneficial properties, against Aspergillus parasiticus under different interacting environmental conditions was evaluated. Studies concerning the lag phase, growth rate and aflatoxin B1 production were carried out in vitro under different regimes of a w (0.95 and 0.99), pH (4 and 6), temperature (25 and 37°C), and oxygen availability (normal and reduced). Both yeast strains showed great antagonistic activity at pH 4, decreasing growth rate compared with the control. The RC008 strain showed the greatest inhibitory activity at all assayed conditions. A. parasiticus produced large amounts of AFB1 in vitro. A significant decrease of AFB1 levels in comparison with the control were observed with yeast interaction. Differences between control and treatment values ranged from 130 to 5400 ng ml−1. S. cerevisiae RC008 and RC016 could be considered as effective agents in reducing growth and AFB1 production at different interacting environmental conditions, related to that found in stored feedstuff. The importance of the present work lies in the search for live strains with both probiotic and biocontrol properties able to prolong the safe storage of feedstuff and exert beneficial properties after animal consumption and which could be included in a novel product for animal feed. [ABSTRACT FROM AUTHOR]

The aim was to evaluate both the ability of yeast strains to survive and bind AFB1under ruminant gastrointestinal conditions and the effect of these yeast strains on ruminal fermentation. Yeast viability was studied under simulated gastrointestinal conditions. AFB1binding ability was evaluated at different pH values as present in the ruminant gastrointestinal tract. The effect of yeast strains on cellulose digestion and volatile fatty acids production by ruminal bacteria was also evaluated. All yeast strains were able to survive under gastrointestinal conditions and to adsorb AFB1at the different pH assayed. The strain RC016 showed the highest binding percentage at the three tested pH. The number of cellulolytic bacteria in ruminal fluid increased in the presence of RC008 and RC016 yeast strains. The concentration of acetate and propionate after ruminal fermentation increased with the addition of RC008 and RC016 strains; this effect was less significant with RC009 strain. Strains RC008 and RC016 are potential probiotic to be included in animal feed: they help to increase fibber digestibility and could reduce AFB1bioavailability in the gastrointestinal tract. ViableS. cerevisiaeRC008 and RC016 strains with both probiotic and mycotoxins adsorption properties could be used as feed additives in ruminant feedstuff. [ABSTRACT FROM AUTHOR]