A direct relationship between jarosite precipitation and the number of atta
ched cells were found in Thiobacillus ferrooxidans cultures in the presence
of glass beads. Low cell immobilisation was observed on the glass beads; t
hese cells were probably attached to the jarosite deposits on the glass. Th
e presence of glass beads only contributed to biofilm formation increasing
jarosite precipitation especially at higher pH values. At a pH value lower
than 1.6, a biofilm was not produced due to negligible iron precipitation.
Cultures with an initial pH value of 1.8 reached an iron(III) productivity
as high as 15 mM h(-1) after five successive cultures obtained by transferr
ing previous solid residues to new media. (C) 2000 Elsevier Science Ltd. Al
l rights reserved.