Bioaccumulation of some hazardous metals by sol-gel entrapped microorganisms

This paper reports immobilization of baker's yeast cells (saccharomyces cerevisiae) by entrapment of the biomass in a sol-gel matrix. The solid biogel was observed to accumulate hazardous heavy metals from aqueous solutions. The metal uptake capacity of the biogels was essentially the same as that of the foe yeast cells for Hg(II) and Cd(II). However, free yeast cells showed better bioaccumulation capacity for Pb(II) and Cu(II) while a lower capacity was observed in the cases of Co(II), Ni(II), and Zn(II). The siloxane based sol-gel entrapment matrix positively contributes to the overall metal uptake of the biogel, which was observed to contain intact yeast cells homogeneously distributed into the solid matrix. The affinity of the biogel for metal ion bioaccumulation followed the order Hg(II)> Zn(II) > Pb(II) > Cd(II) > Co(II) = Ni(II) > Cu(II). Metal uptake characteristics of the biogel also depend on pH, buffer type and temperature. (C) 1999 Published by Elsevier Science B.V. All rights reserved.