P. Simmons et I. Singleton, A METHOD TO INCREASE SILVER BIOSORPTION BY AN INDUSTRIAL STRAIN OF SACCHAROMYCES-CEREVISIAE, Applied microbiology and biotechnology, 45(1-2), 1996, pp. 278-285
Ag+ biosorption by an industrial strain of Saccharomyces cerevisiae wa
s investigated. Older (96 h old) biomass had half the biosorption capa
city of younger (24 h old) biomass (0.187 and 0.387 mmol Ag+/g dry mas
s respectively). Comparisons of cell walls isolated from biomass of ei
ther age indicated that chemical composition and Ag+ biosorption capac
ity varied little over the time span examined and that cell walls from
either age of culture had small Ag+ biosorption capacities compared t
o whole cells of a similar age. Silver-containing precipitates were ob
served both on the cell wall and within the cell, indicating that intr
acellular components sorbed Ag+ The concentration of these precipitate
s within the cell appeared visually to decrease with age in Ag+-expose
d cells. Incorporation of L-cysteine into the growth medium resulted i
n biomass with increased silver biosorption capacities, protein and su
lphydryl 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 bios
orption capacities, protein and sulphydryl group content. No precipita
tes were observed in silver-exposed biomass that had been grown in the
presence of 5.0 mM L-cysteine.