title: A method to increase silver biosorption by an industrial strain of Saccharomyces cerevisiae.
abstract: Ag+ biosorption by an industrial strain of Saccharomyces cerevisiae was investigated. Older (96 h old) biomass had half the biosorption capacity of younger (24 h old) biomass (0.187 and 0.387 mmol Ag+/g dry mass respectively). Comparisons of cell walls isolated from biomass of either age indicated that chemical composition and Ag+ biosorption capacity varied little over the time span examined and that cell walls from either age of culture had small Ag+ biosorption capacities compared to whole cells of a similar age. Silver-containing precipitates were observed both on the cell wall and within the cell, indicating that intracellular components sorbed Ag+. The concentration of these precipitates within the cell appeared visually to decrease with age in Ag(+)-exposed cells. Incorporation of L-cysteine into the growth medium resulted in biomass with increased silver biosorption capacities, protein and sulphydryl group content. Increasing the concentration of L-cysteine in the growth medium from 0 to 5.0 mM increased silver biosorption from 0.389 to 0.556 mmol Ag+/g dry mass. Isolated cell walls of biomass grown in supplemented media also showed a possible link between silver biosorption capacities, protein and sulphydryl group content. No precipitates were observed in silver-exposed biomass that had been grown in the presence of 5.0 mM L-cysteine.
authors.affiliation: Department of Industrial Microbiology, University College Dublin, Ireland.
authors.forename: P
authors.initials: P
authors.lastname: Simmons
authors.forename: I
authors.initials: I
authors.lastname: Singleton
mesh_terms: D000327:Adsorption; D001426:Bacterial Proteins / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D003545:Cysteine / Q000494:pharmacology; D004577:Electron Probe Microanalysis; D008854:Microscopy, Electron; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D012834:Silver / Q000493:pharmacokinetics*; D012996:Solutions; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012996:Solutions; D013438:Sulfhydryl Compounds; D012834:Silver; D003545:Cysteine