菲降解菌的降解特性及酶促反应动力学研究

通过对取自MBR膜生物反应器中的活性污泥加入菲进行富集培养、驯化,分离、纯化出一株能以菲为唯一碳源和能源的短杆状革兰氏阴性菌J-1,细菌长2～5μm,宽1～3μm;研究了初始底物浓度、温度、pH对菌株J-1降解菲的影响,探讨了菌株J-1胞内酶对菲降解的底物抑制动力学。试验表明:菌株J-1在48h内能将不同浓度菲的水溶液中的菲完全降解;菲浓度增加,达到完全降解的时间延长。温度对细菌的降解能力影响较大,菌株J-1对菲降解的最佳温度为28℃。1.15mg·L-1的菲,28℃时48h内能完全降解,而相同时间内10℃时的降解率仅为36.65%。菌株J-1对pH的波动具有一定的适应性,pH在一定范围内(6.0～8.4)变化对菲降解的影响不大,降解反应的最佳pH为7.2。菌株J-1对菲的降解符合一级动力学反应方程。较高的底物浓度对酶促降解反应具有抑制作用,酶促反应的最大速率常数vm=1.17mg·L-1·h-1,米氏常数Km=61.70mg·L-1;底物抑制常数kS=49.60mg·L-1;最佳底物浓度S]opt=55.32mg·L-1。

Biodegradation characteristis and enzqmatic rcaction kinetics of phenanthrene-degrading bacteria

The effects of initial substrate concentration,temperature and pH on the phenanthrene biodegradation characteristics and enzymatic reaction kinetics were studied by using a strain of gram-negative bacteria J-1 that is isolated and purified from the active sludge.The sludge collected from Membrane Bioreactor was cultured and acclimated with phenanthrene.The bacteria cells,in the shape of a short rod,are about 2-5 μm long and 1-3 μm wide.The phenanthrene in the aqueous solution was completely degraded in 48 h,however,the biodegradation time prolonged when the initial concentration increased.The temperature had significant effect on the phenanthrene biodegradation by strain J-1.The optimum temperature of the biodegradation was 28 ℃.With the same initial concentration of phenanthrene,the biodegradability of phenanthrene was found to be decreased with increasing or decreasing the temperature.100% of the phenanthrene was degraded in 48 h for the concentration of 1.15 mg·L-1 when the temperature was 28 ℃.However,less than 37% of phenanthrene could be degraded,if the temperature was decreased to 10 ℃.The biodegradation ability of the strain J-1 had a certain adaptability with the variety of pH between 6.0-8.4 and the optimum pH was 7.2.The experimental outcomes could be fit well with the first-order biodegradation kinetics model.The high substrate concentration inhibited the enzymatic reaction.The maximum rate constant vm,Michaelis constant Km,substrate inhibition constant kS,and the optimum substrate concentration S]opt of the enzymatic reaction were 1.17 mg·L-1·h-1,61.70 mg·L-1,49.60 mg·L-1,and 55.32 mg·L-1,respectively.