Isolation And Effect Of An Aniline-degrading Bacteria Stain Named DK

Aniline is not only essential chemical materials for industrial production but also one of the refractory pollutants. Now, the degradation of excessive aniline in environment is getting more and more attention. Compared with other methods, microbial degradation was lower cost, high efficiency and without secondary pollution. The key link in this method was screening microbe with effect aniline degradation. So this paper mainly studied the domestication of aniline efficiency degradation bacteria, screening and isolation and identification of the bacteria, confirming the optimization of growth conditions and the influence of various factors on the degradation rate.In order to screen aniline degrading bacteria from activated sludge, we began to put the activated sludge in the enrichment culture medium for enrichment culture, then transferred to the selective medium from enrichment medium, plating and streaking and purified culturing. The strain DK was isolated from activated sludge which degraded half of the aniline in the selective medium in three days. And the concentration of aniline in the minimal medium was 1000mg/L. The screened bacteria stain DK was gram-negative and belonged to Delftia sp. identified by gram stain, physiological and biochemistry characteristics,16S rDNA sequencing and analysis of phylogenetic tree based on 16S rDNA sequence.In the optimization of growth conditions experiments, effects of the temperature, pH, rotation speed and aniline concentration were investigated in LB medium through orthogonal test. The effect order of four factors on strain DK growth:pH>rotation speed>temperature>aniline concentration. And the result of optimal growth conditions in LB medium:temperature was 32℃, pH was 6, rotation speed was 250r/min and aniline concentration was Omg/L. Through single factor experiment, the result of optimal growth conditions in minimal medium:culturing time was 54h, temperature was 32℃, pH was 6. On this condition, stain DK’s growth curve in minimal medium was rendered. Strain DK was kept alive in minimal medium with high aniline concentration. The maximum tolerance was 3500mg/L.Through single factor experiment, we studied the effect of temperature, pH and bacterial suspension inoculation on the aniline degradation rate. The result of optimal degradation condition for stain DK:temperature was 32℃ and pH was 7. Not the both conditions were the same with optimal growth conditions. And the more bacterial suspension inoculation quantity, the faster degradation of aniline. Stain DK degraded aniline rapidly in minimal medium with low aniline concentration and slowly with high aniline concentration. It showed that aniline was not only carbon and nitrogen source, but also can inhibit the growth of strain DK with high concentration. Both Fe2+ and Cu2+ can promote aniline degradation, and the former was better. While Cr (VI) and Al3+ inhibited DK’s ability to degrade aniline, and the former was particularly significant. Effects of external carbon source and nitrogen source showed that glucose promoted the degradation while lactose, sucrose, sodium nitrate can inhibit the degradation. In the three different degradation system, including ultra pure water, tap water and lake water, the degradation of aniline in tap water was fastest and the degradation rate would be 87.4%. This research achieved the strain DK which can degrade aniline effectively. Appropriate growth conditions of the strain DK and many factors’ influence on the degradation rate were confirmed in this paper. All the result in this paper could provide materials and theoretical basis for further research. It showed that stain DK had the potential for practical application seen from the degradation effect.