Isolation,identification and hexavalent chromium reduction studies of Bacillus cereus S5.4

Hexavalent chromium,regarded as one of the most dangerous pollutants among heavy metals in the environment for its toxicity to living organisms,is being widely studied for its bioremediation.More and more microorganisms showing steady resistance and reduction ability of hexavalent chromium were identified,but few of them were applied to industrial fields.A series of bacteria with high resistance of hexavalent chromium were isolated from the electroplating sludge of Baosteel Corporation,Shanghai.A strain named S5.4,which showed high reduction ability of hexavalent chromium,was identified as Bacillus cereus by morphological,physiological and biochemical characteristics and its 16s rDNA sequence.Under the aerobic conditions,this strain was able to grow on LB plates with 40mmol/L Cr6+ after 48h,and also showed high endurance on Mn2+,Ba2+ and Mo6+.At the same time,this strain was able to completely reduce 2 mmol/L Cr6+ in LB liquid after 72 h,and work continuously with supplement of cultural medium and hexavalent chromium.For reducing hexavalent chromium,the optimal concentration,temperature range and pH range were 2mmol/L Cr6+,30～37℃ and pH 7～9,respectively.