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Biosorption of Cr(III) by the cell wall of Mucor
hiemalis Biosorption
of chromium(III) by whole cells and isolated cell walls of Mucor hiemalis was
investigated. A fast initial sorption of Cr(III) on the cell wall was found, reaching 80%
of the calculated maximum load after 30 min contact time. However, the final biosorption
maximum could not be reached after two hours, indicating a complex binding mechanism
comprising more than one sub-process. From the Langmuir-fitted biosorption isotherms
theoretical maximum biosorption capacities of 132 and 22 mg Cr(III)/g d.w. were calculated
for cell wall and whole cells, respectively. The composition of isolated cell walls was
studied. The major components were chitosan (32%) and chitin (11%). The type of nitrogen
source in the cultivation medium (NaNO3 and peptone from casein) strongly
influenced the cell wall composition. The contents of chitosan and phosphorus in the cell
wall were significantly higher with NaNO3 in comparison to peptone from casein,
whereas a higher protein content was found using peptone. The biomass and extracted cell
walls with higher contents of chitosan and phosphorus, deriving from the cultivation with
NaNO3, showed an increased biosorption capacity for Cr(III). These results
indicate that chitosan and phosphorus containing functional groups are the most probable
binding sites for trivalent chromium in the cell wall, whereas proteins do not play a role
in the biosorption of Cr(III) by Mucor hiemalis.
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