Hexavalent chromium reduction by Acinetobacter haemolyticus isolated from heavy-metal contaminated wastewater

摘要

Possible application of a locally isolated environmental isolate, Acinetobacter haemolyticus to remediate Cr(Ⅵ) contamination in water system was demonstrated. Cr(Ⅵ) reduction by A. haemolyticus seems to favour the lower concentrations (10-30mg/L). However, incomplete Cr(Ⅵ) reduction occurred at 70-100 mg/L Cr(Ⅵ). Initial specific reduction rate increased with Cr(Ⅵ) concentrations. Cr(Ⅵ) reduction was not affected by 1 or 10mM sodium azide (metabolic inhibitor), 10mM of PO_4~(3-), SO_4~(2-), SO_3~(2-), NO_3~- or 30 mg/L of Pb(Ⅱ), Zn(Ⅱ), Cd(Ⅱ) ions. However, heat treatment caused significant dropped in Cr(Ⅵ) reduction to less than 20% only. A. haemolyticus cells loses its shape and size after exposure to 10 and 50 mg Cr(Ⅵ)/L as revealed from TEM examination. The presence of electron-dense particles in the cytoplasmic region of the bacteria suggested deposition of chromium in the cells.