Removal of toxic chromate using free and immobilized Cr(VI)-reducing bacterial cells of Intrasporangium sp. Q5-1

摘要

Chromate-reducing microorganisms with the ability of reducing toxic chromate [Cr(VI)] into insoluble trivalent chromium [Cr(III)] are very useful in treatment of Cr(VI)-contaminated water. In this study, a novel chromate-reducing bacterium was isolated from Mn/Cr-contaminated soil. Based on morphological, physiological/biochemical characteristics and 16S rRNA gene sequence analyses, this strain was identified as Intrasporangium sp. strain Q5-1. This bacterium has high Cr(VI) resistance with a MIC of 17 mmol lp# and is able to reduce Cr(VI) aerobically. The best condition of Cr(VI) reduction for Q5-1 is pH 8.0 at 37pC. Strain Q5-1 is also able to reduce Cr(VI) in resting (non-growth) conditions using a variety of carbon sources as well as in the absence of a carbon source. Acetate (1 mmol lp#) is the most efficient carbon source for stimulating Cr(VI) reduction. In order to apply strain Q5-1 to remove Cr(VI) from wastewater, the bacterial cells were immobilized with different matrices. Q5-1 cells embedded with compounding beads containing 4% PVA, 3% sodium alginate, 1.5% active carbon and 3% diatomite showed a similar Cr(VI) reduction rates to that of free cells. In addition, the immobilized Q5-1 cells have the advantages over free cells in being more stable, easier to re-use and minimal clogging in continuous systems. This study provides potential applications of a novel immobilized chromate-reducing bacterium for Cr(VI) bioremediation.