Hexavalent Chromium Reduction at Different Growth Phases ofAcinetobacter haemolyticus

Abstract

Abstract The aim of this work was to evaluate the effects of hexavalent chromium [Cr(VI)] addition at different growth phases on the Cr(VI) reducing capacity of the aerobic Gram-negative bacterium, Acinetobacter haemolyticus. The addition of 10–100 mg Cr(VI) L−1 as potassium dichromate at the time of inoculation (T0) resulted in the extension of time needed to reach the stationary phase, with a total growth inhibition at 70 mg Cr(VI) L−1, a decrease in bacterial count from 108 to 102 CFU mL−1, and a Cr(VI) reduction drop to 35% at 100 mg Cr(VI) L−1. However, bacterial growth was uninterrupted when 10–100 mg Cr(VI) L−1 were added at the early stationary phase (after 12 h of bacterial growth) indicated by a high bacterial count of 108 CFU mL−1. More than 95% of Cr(VI) was reduced at an initial Cr(VI) of 50 mg L−1. However, the Cr(VI) reduction capacity dropped to 50% at 100 mg Cr(VI) L−1. This study showed that the ability of Acinetobacter haemolyticus to reduce Cr(VI) depends strongly on the number of surv...