Investigation of copper and lead tolerance and biosorption by three standard yeast strains

Environmental pollution by heavy metals has become one of the most serious environmental issues today. In past years، various physical and chemical methods were evaluated and tested to remove heavy metals، but most of them happen to be tough or hazardous، complex، incomplete، expensive moreover requiring lot of energy. Using microorganisms as adsorbents for removal of heavy metal offers a potential alternative to mentioned methods. In this study، three standard yeast including Saccharomyces cerevisiae PTCC 5052، Kluyveromyces marxianus DSMZ5422 Yarrowia lipolytica DSMZ 8218، was used. Resistance of yeast to different concentrations of copper and lead were measured، The yeast were more resistant towards copper (up to 6mM by Y. lipolytica، 5mM by K. marxianus and 1mM by S. cerevisiae) and less resistant towards lead (up to 2mM by the used yeasts). Then based on the observed resistance of the yeast، their ability in metal absorption was examined. Yeast metal uptake at concentrations that they were sensitive، were more. The maximum uptake by the yeasts were 168mg/ g dry weight (g dry W) copper and 54. 6mg/g dry W lead by S. cerevisiae، 75. 56mg/g dry W from copper and 67. 46mg/g dry W from lead by K. marxianus، and 696mg/g dry W copper and 69. 66mg/g dry W from lead by Y. lipolytica. Another test was performed to investigate the effect of glucose on uptake in low concentrations. It was observed that glucose was ineffective on absorption which is energy-independent and effective on bioaccumulation which is energy-dependant.