Studies On The Degradation And Mechanism Of Nitrogenous Heterocyclic Compounds Using White Rot Fungus

Nitrogenous heterocyclic compounds are the common organic pollutants in industrial wastewaters, such as coking plants, printing and dying plants, pesticide plants and so on. They make the wastewaters difficult to be biodegraded. Most nitrogenous heterocyclic compounds can cause cancer and limb malformation and have potential harm to environment and human being, so it is benefit to environment protection and people's health keeping by the degradation studies of nitrogenous heterocyclic compounds. White rot fungi have non-specific ability, thoroughness, broad spectrum property and suitable to solid or liquid medium cultivation to degrade pollutants. In this paper white rot fungi were used to degrade nitrogenous heterocyclic compounds in the simulated and coking plant wastewater. The main research results of this paper include:1. Characteristic analysis of white rot fungus in different fermentation system. In the liquid culture systems, the optimized growth and excreting laccase fermentation conditons of white rot fungus (Pleurotus sp.) were non-buffering system of pH 5.0, rotating speed 150 rpm, 100 mL culture medium per 250 mL flask. In the solid culture systems, white rot fungi could produce much more laccase and has more obivious multi-peak phenomenon in chip solid condition, while white rot fungi had more biomass in corn stalk and rice stalk solid culture systems.2. Removal and mechanism analysis of solo-substrate of nitrogenous heterocyclic compounds by white rot fungi in the liquid culture systems.In the degradation systems of quinoline, the kinetics of low concentration quinoline biodegradation could be described by zero-order reaction rate equation, while the kinetics of high concentration quinoline biodegradation could be described with first-order model. In the degradation systems of low concentration quinoline, the relative degradation rate of quinoline was close correlated with the activity of laccase , rate of biomass production. When the activity of laccase and rate of biomass production were peak values, the relative degradation rate of quinoline reached maximus values.In the degradation systems of indole, the kinetics of indole biodegradation could be described by first-order reaction rate equation. The degradation rate of indole was highly related with the activity of laccase. The growth of white rot fungi and the production of laccase were inhibited completely when the concentration of indole was 400 mg/L in synthetic liquid media. The biodegradation process of indole by white rot fungi was one-step oxidation at 2- and 3-position simultaneously and followed by hydroxylation and cleavage of the pyrrole ring between 2- and 3- positions. The NH3-N and phenol as co-substrates of indole could promote degradation of indole, improve peak values of the activity of laccase and rate of biomass production, shorten the metabolism periods of laccase secretion and white rot fungi's production.3. Treatment of solo-substrate of nitrogenous heterocyclic compounds by white rot fungi in the solid culture systems.In rice straw solid cuture, nitrogenous heterocyclic compounds could be removed more effectively. Laccase secreted by the white rot fungus played important roles in the degradation process of nitrogenous heterocyclic compounds.4. Studies on co-substrate of nitrogenous heterocyclic compound by white rot fungi in the liquid culture systems.The co-effect of pyridine mixed with quinoline showed a contradictory effect, while the co-effect of pyridine and quinoline respectively mixed with indole showed a cooperative effect. Degradation of quinoline of co-substrate systems was inhibited by NH3-N, while phenol could promote degradation of quinoline. Compare to the solo-substrate degradation systems, white rot fungi in the co-substrate degradation systems had higher activity of laccase and rate of biomass production, and the metabolism periods of laccase secretion and white rot fungi's production were shorten. NH3-N and phenol could improve laccase secretion ability of white rot fungi in co-substrate degradation systems.5. Biodegradation of nitrogenous heterocyclic compounds in a coking plant wastewater by white rot fungi.Nitrogenous heterocyclic compounds in a coking plant wastewater could be removed quickly by white rot fungi. The kinetics of quinoline biodegradation could be described by first-order reaction rate equation, while the kinetics of indole biodegradation could be described with zero-order model. Production of white rot fungi and degradation of quinoline could be promoted by Mg2+ and Mn2+. Cu2+ could improve laccase secretion ability, but inhibit production of white rot fungi. Laccase secretion of white rot fungi in the coking plant wastewater was inhibited, and rate of biomass production was on a much lower level.