Researches On Phenol Biodegradation By The Two Strains Isolated From Active Sludge

Phenol has been used in numerous fields, and industrial effluentincluding phenol is largely discharged. Biodegradation is economical，mild，thoroughgoing，so It’s very popular, among which,the way ofseparating efficiency phenol-degrading strains is often the case.This isexactly the characteristic of wide microbial metabolism types. Theco-mebotalism principle and optimization for phenol removal by thebinary of the two strains XTT-1，XTT-3to achieve the optimal effect wasexplored.First,Two phenol-degrading bacterial strains named XTT-1,XTT-3were isolated according to the way of acclimatization. XTT-1, XTT-3wereidentified as Delftia sp.and Sphingomonas sp. by physiological,biochemical and16S rDNA identification. Delftia sp. has never beenreported. No antagonism exists between the two strains.Then optimizingthe factors impacting phenol biodegradation by XTT-1, XTT-3wasexplored. The appropriate condition for phenol removal by XTT-1is250r/min of rotation speed,pH7.0,30℃, OD6000.8of cell density,2%ofinoculum concentration,NaCl<1%and under this condition,phenol(500mg/L) can be removed completely in64h by XTT-1. ForXTT-3,It is250r/min of rotation speed,pH8.0～8.5,30℃, OD6000.2of celldensity,2%of inoculum concentration,NaCl<1%, phenol(500mg/L) canbe removed completely in48h.For the two strains,and the capacity towithstand phenol concentration can’t exceed1000mg/L.Phenol was removed slowly by the two strains using phenol assole carbon. With0.2g/L yeast extract and30mg/L catechol in mineralsalt medium,500mg/L phenol can be removed69%by XTT-1,the rate is0.128mg/min. With0.2g/L yeast extract and20mg/L catechol in minsalt medium,500mg/L phenol can be removed absolutely by XTT-3,therate is0.184mg/min. The binary mixed culture of the two strains（each OD6000.4）withequal volumes showed excellent results for phenol removal. PH, phenolconcentration and inoculation were the previous three factorsinfluencing the phenol removal by the Plackett-Burman design. Underthe condition of pH6.0, phenol(500mg/L) can be removed absolutely in28h by the binary mixed culture after optimizing the three factors. Thephenol removal rate decreased with the phenol concentration andincreased with inoculum concentration.