LEACHING OF ZINC FROM AN INDUSTRIAL FILTER DUST WITH PENICILLIUM, PSEUDOMONAS AND CORYNEBACTERIUM - CITRIC-ACID IS THE LEACHING AGENT RATHER THAN AMINO-ACIDS

Heterotrophic microorganisms are able to solubilize metals via excrete d metabolites-most often di- or tricarboxylic acids but also amino aci ds. With amino acids Cu, Zn, Au, Ni, U, Hg and Sb have been solubilize d from metal oxides, metal sulfides or elementary metals. In this work it was investigated if excreted amino acids play a role in the leachi ng of zinc from a zinc oxide containing industrial Biter dust. Two bac teria-Pseudomonas putida and Corynebacterium glutanicum-and a fungus-P enicillium simplicissimum were used. P. putida and P. simplicissimum h ave already been used to solubilize zinc oxide, whereas C. glutamicum was used because of its known ability to excrete amino acids. Amino ac ids in culture fluids were analyzed via derivatization with phenyl iso thiocyanate, separation on a RP-18 column and UV-detection. All three microorganisms solubilized zinc from the filter dust and excreted much more citric acid than amino acids. Thus citric acid rather than amino acids was regarded to be the leaching agent. Of the two bacteria P. p utida was more resistant towards the heavy metal-containing filter dus t.