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 30min 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 22mg 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. © 2002 SDU. All rights reserved.