Abstract: From the bottom mud of Qiusuo Creek, a strain Ylb10 with high efficiency in reducing Cr(VI) was successfully isolated and obtained. The Ylb10 strain was identified by physiological and biochemical methods and 16S rDNA sequencing method, and the Cr(VI) was determined by diphenylcarbazide spectrophotometry to investigate its reduction characteristics. The results showed that Ylb10 was Gram-negative, and the 16S rDNA similarity rate with Alicycliphilus denitrificans was 98.07%. Ylb10 could make good use of α-hydroxy-butyric acid, L-lactic acid, propionic acid, acetic acid, L-aspartic acid, L-glutamic acid, L-alanine, L-erine and other substrates.Compared that with the shaker culture conditions, Cr(VI) could be better reduced during standing culture, and the optimal pH of Cr(VI) reduction was 8-9. When the concentration of Cr(VI) was lower than 200 mg/L, the strain could reduce all Cr(VI), of which, at 50 mg/L Cr(VI) concentration, it had a reduction rate of 96.45% in 18 hours; at 100 mg/L Cr(VI ), it had the reduction rate of 93-83% in 24 hours, and the reduction efficiency at 200 mg/L Cr(VI) concentration in 60 hours was 99.06%. It could be concluded that Alicycliphilus denitrificans Ylb10 was a high-efficiency hexavalent chromium reducing bacteria, and It had high application potential in the treatment of chromium-contaminated water quality and soil.

Key words: Alicycliphilus denitrificans, Cr(VI) reducing bacteria, heavy metals, bioremediation of chromium pollution