Removal of heavy metals using a brewer's yeast strain of Saccharomyces cerevisiae: the flocculation as a separation process.

In this work, a brewer's yeast strain was used to remove heavy metals from a synthetic effluent. The solid-liquid separation process was carried out using the flocculation ability of the strain. The yeast strain was able to sediment in the presence of Cu2+, Ni2+, Zn2+, Cd2+ and Cr3+, which evidences that the flocculation can be used as a cheap and natural separation process for an enlarged range of industrial effluents. For a biomass concentration higher than 0.5 g/l, more than 95% of the cells were settled after 5 min; this fact shows that the auto-aggregation of yeast biomass is a rapid and efficient separation process. Cells inactivated at 45 degrees C maintain the sedimentation characteristics, while cells inactivated at 80 degrees C lose partially (40%) the flocculation. The passage of metal-loaded effluent through a series of sequential batches allowed, after the second batch, the reduction of the Ni2+ concentration in solution for values below the legal limit of discharge of wastewater in natural waters (2mg/l); this procedure corresponds to a removal of 91%. A subsequent batch had a marginal effect on Ni2+ removal (96%). Together, the results obtained suggest that the use of brewing flocculent biomass looks a promising alternative in the bioremediation of metal-loaded industrial effluents since the removal of the heavy metals and cell separation are simultaneously achieved.