| Quinoline is a typical nitrogen-containing heterocyclic organic compound widely found in coking,steel,pharmaceutical and printing and dyeing wastewater.It is fused by a benzene ring and a pyridine ring,so it is also called benzopyridine.It is the basic structural unit of a large number complex nitrogen-containing heterocyclic compound Quinoline is highly toxic,teratogenic and carcinogenic to humans and animals.Therefore,the treatment of quinoline-containing pollutants has always been a maj or problem in the field of water treatment.Microbial method is a cost-effective way to remove quinoline pollutants in the environment,but the problem of how to improve the degradation efficiency of quinoline has not been solved.Therefore,it is of great theoretical value and practical significance to study the conditions for rapid degradation of quinoline by strains.Based on previous research results,the characteristics and mechanism of quinoline oxidoreductase were studied,and the degradation properties of the immobilized mixed bacteria on quinoline were studied.The following research results were obtained(1)The quinoline 2-oxidoreductase(Qor)enzyme activity detection system was optimized by response surface method.The optimized system was Tris-HCl buffer(0.1 mmol· L-1,pH 8.0)2 mL,TritonX-100(mass concentration was 1%)0.06 mL,Iodonitrotetrazolium Chloride(INT)2 mL,quinoline 0.3 mL,and intracellular enzyme solution 0.6 mL.What is more,the optimum temperature and pH of the quinoline 2-oxidoreductase were 37? and 8.0(2)0.05 mmol·L-1 Mo6+,1%Tween 80 and 5 mmol·L-1 formic acid can increase the quinoline 2-oxidoreductase activity by 1.4 times,3.11 times and 1.52 times,respectively.And then,quinoline 2-oxidoreductase has substrate specificity.The kinetics of the enzymatic reaction indicated that Qor catalyzed quinoline with a michaelis constant(Km)of 0.92 mmol·L-1 and the maximum reaction rate of 0.17 U·mg-1,so the binding force between quinoline oxidoreductase and substrate quinoline was relatively large.(3)The quinoline with a initial concentration of 300 mg·L-1 can be completely degraded within 22?28 h after the combination of inducer Mo6+,formic acid and Tween 80 is added in the strain LC-1 degradation quinoline system.In addition,the main reason for the enhancement of quinoline biodegradation is that the inducible factors can greatly increase the enzyme activity(4)The properties of PVA/ZnONPs were characterized by using X-ray diffractometer(XRD)and scanning electron microscopy(SEM)analysis.The results showed that the ZnONPs were evenly distributed on porous surface of the PVA/ZnONPs,which enhanced the adsorption of bacteria and quinoline.In addition,the PVA/ZnONPs with multiple porosities could provide enough space to support bacterial growth,and the carrier had good quinoline adsorption and biocompatibility,the mass transfer distance was greatly shortened(5)During the process of quinoline degradation,quinoline 2-oxidoreductase(Qor)activity in the immobilized mixed cells was 1.7 times higher than that of free mixed cells.Under the condition of the initial concentrations of quinoline was 500 mg·L-1,the degradation rate of the quinoline by the immobilized mixed cells was 99.8%within 10 h,which was much higher than that of the free mixed cells(43.2%),the results demonstrated that the quinoline degrading ability of mixed strains were enhanced drastically after being immobilized.Furthermore,When the initial concentrations of quinoline were from 600 to 800 mg·L-1,the degradation rate of quinoline by immobilized mixed cells could be more than 99%,after 30 times of reuse,the degradation rate of quinoline remained above 99.9%,and the immobilized carrier showed good mechanical tolerance,which could be used in production practice... |
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