Risk of low stability Saccharomyces cerevisiae ATCC 9763-heavy metals complex in gastrointestinal simulated conditions

The biosorption of heavy metals by microorganisms has attracted the interest of food researchers as the last approach to reduce the risk of their absorption in the human body. But the stability of yeast-metal complexes under simulated gastrointestinal conditions has not been investigated. In this study stability of complex as well as isotherm and kinetic models of biosorption have been studied. Also, the impact of some pretreatment on yeast biosorption was studied to check the possible impact of different environmental conditions in food processing. Data showed a risk of heavy metal release in simulated gastrointestinal conditions. The best biosorption of metals from aqueous solutions by Saccharomyces (S.) cerevisiae may be achieved after NaOH pretreatment for Mercury (Hg) 92.7%. While biosorption of Lead (Pb) 37.48%, Arsenic (As) 19.44%, and Cadmium (Cd) 39.9% by untreated yeast were better. In gastrointestinal conditions, Hg and Cd-yeast complexes were more stable and biosorption of Cd and Pb increased. Bonds of As and Hg-yeast complexes in digestion conditions were reversible. The metals biosorption by untreated yeast followed the pseudo-second-order kinetic and the Langmuir isotherm model for Hg, Pb, and Cd and Freundlich for As. Results showed that biosorption of heavy metals by S. cerevisiae, although may decrease metal bioavailability in fermented foods, the complex is not enough stable in gastrointestinal conditions.