Chemical and enzymatic extraction of heavy metal binding polymers from isolated cell walls of Saccharomyces cerevisiae

Abstract

Isolated cell walls of the yeast Saccharomyces cerevisiae were treated by either chemical (alkali and acid) or enzymatic (protease, mannanase or beta-glucuronidase) processes to yield partially purified products. These products were partially characterized by infrared analysis. They were subsequently reacted with heavy metal cation solutions and the quantity of metal accumulated by the cell wall material determined. The Cu(2+) ion (0.24, 0.36, 1.12, and 0.60 micromol/mg) was accumulated to a greater extent than either Co(2+) (0.13, 0.32, 0.43, and 0.32 micromol/mg) or Cd(2+) (0.17, 0.34, 0.39, and 0.32 micromol/mg) by yeast cell walls, glucan, mannan, and chitin, respectively The isolated components each accumulated greater quantities of the cations than the intact cell wall. Removal of the protein component of the yeast cell walls by Pronase caused a 29.5% decrease in metal accumulation by yeast cell walls per mass, indicating the protein is a heavy metal accumulating component. The data indicate that the outer mannan-protein layer of the yeast cell wall is more important than the inner glucan-chitin layer in heavy metal action accumulation.