Chromium detoxification and phenol degradation by bacterial isolates

Abstract

Three strains of 150 strains of chromium-resistant bacterial isolates (2400 mug/ml) were selected and named CrR-2, CrR-14 and CrR-15. By some identification test, they might be classified as Escherichia sp., Pseudomonas sp. and Enterobacter sp., respectively. Three strains of 225 strains of phenol-resistant bacterial isolates (2000 mug/ml) were selected and named PhR-26, PhR-33 and PhR-64. By some identification test, they might be classified as Klebsiella sp., Pseudomonas sp. and Escherichia sp., respectively. Three strains of 120 strains of chromium/phenol-resistant bacterial isolates (1200 mug/ml) were selected and named CPR-4, CPR-16 and CPR-17. By some identification test, they might be classified as Pseudomonas sp., Proteus sp. and Escherichia sp., respectively. Optimum pH and temperature for growth and chromium detoxification and phenol degradation were 7 and 37 ํC. The efficiency of chromium detoxification and phenol degradation appeared maximally during the exponential phase (incubation period; 6 hr.) and contact time (15 min.). Addition of phenol in culture was increased growth of bacterial isolates because phonol as carbon and energy sources, and were also in culture, added chromium, so simultaneous chromium detoxification and phenol degradation. In coculture and chromium/phenol-resistant bacterial isolates found that Cr(VI) detoxification and phenol degradation are high efficiency (more than 80%), but not much different. Cr(III) production found that generated just a little (less than 20%) because Cr(VI) passes through cell membranes and then is reduced to Cr(III) inside the cell stable binds to protein. Those bacterial isolates can degrade derivatives of phenol, i.e., p-cresol within 2 weeks and more than 3 weeks to degrade p-chlorophenol and p-nitrophenol. So efficiency of CPR-resistant bacterial isolates is better than the coculture because of usage a little time and low cost in work at twice in order to be so far efficiency.