Leaching of zinc from an industrial filter dust with Penicillium, Pseudomonas and Corynebacterium: Citric acid is the leaching agent rather than amino acids

Abstract

Heterotrophic microorganisms are able to solubilize metals via excreted metabolites-most often di- or tricarboxylic acids but also amino acids. With amino acids Cu, Zn, Au, Ni, U, Hg and Sb have been solubilized from metal oxides, metal sulfides or elementary metals. In this work it was investigated if excreted amino acids play a role in the leaching of zinc from a zinc oxide containing industrial filter dust. Two bacteria-Pseudomonas putida and Corynebacterium glutamicum-and a fungus-Penicillium simplicissimum were used. P. putida and P. Simplicissimum have already been used to solubilize zinc oxide, whereas C. glutamicum was used because of its known ability to excrete amino acids. Amino acids in culture fluids were analyzed via derivatization with phenyl isothiocyanate, 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. putida was more resistant towards the heavy metalcontaining filter dust. © 1995 Society for Industrial Microbiology.