Bioreduction of Cr(VI) by Raoultella ornithinolytica BCA13 Obtained from Tannery Effluent

Cr(III) is indissoluble and shows less toxicity against Cr(VI). Therefore, it is very important to reduce Cr(VI) to Cr(III) by appropriate methods. In the current study, reduction studies of Cr(VI) to Cr(III) by bioremediation method were performed, which is an economical, efficient, and environmentally friendly method. For this, 13 chromium resistant bacteria were obtained from leather industry wastewater of the Gerede-Bolu region of Turkey. As a Cr(VI) source, solutions containing K2Cr2O7 and CrO3 at different concentrations (25-500 mg/L) were prepared separately in nutrient broth, and their minimum inhibitory concentrations (MIC) were determined. BCA13 isolate, which was molecularly identified by 16S rDNA analysis, has the highest MIC value (500 mg/L). The reduction impact of BCA13 isolate in Cr(VI) at different pH conditions (4.0-10.0) was detected. The optimum pH condition was pH 6.5. It was observed that at pH 6.5, BCA13 isolate completely reduced 50, 100, 150, 200, and 250 mg/L Cr(VI), at 32(nd), 56(th), 64(th), 80(th), and 96(th) h, respectively. BCA13 strain could be used in biodegradation studies because it has the ability to reduce at high chromium concentrations.