Aerobic Biodegradation Of Nonylphenol And Kinetics

Nonylphenol(NP) is one of the most representation alkylphenol compounds inenvironmental hormone pollutants. The fact that the large using of nonylphenol,also its minice estrogenic activity in human and animals has caused increasingconcern about its impact on wildlife and human health and has resulted in calls fora better understanding of how it is degraded in environment. In this study, we studythe biodegradation characteristics of nonylphenol, degradation mechanism,kinetics and the soil bioremediation technology.The results would provide atheoretical basia for biological technology and reference in nonylphenol pollution.In this work we used three strains for nonylphenol degradation experiments,they were Candida tropicalis, Rhodotorula sp., Trichosporon sp.. The resultsshowed that all of them can degrade nonylphenol.The emphasis of our study was put on the effects of temperature, pH, rotationspeed, nitrogen resource on the growth of the three bacterias and theirs degradationactivity of nonylphenol, the optimal reaction conditions were:28℃, pH=6,150rpmand nitrogen source was the organic nitrogen source. In the systems the growth rateof bacteria showed a significant increase and improve by using the carbon resourceand nonylphenol as co-substrates; But the degradation of nonylphenol changedslightly. As the increasing of the concentration of nonylphenol, the pure and mixedbacterias’ degradation activity was inhibited. So the tolerant nonylphenol density ofthem were110,160,110mg/L. At low density of nonylphenol (0~22mg/L) mixedbacteria did not show significant degradation advantages, but in higher density(22~110mg/L), the degradation rate of mixed bacteria was higer than pure strain.The results showed that higher concentrations of beneficial bacteria mixeddegradation of nonylphenolIn this study thus foucsed on much needed information on biodegradationkinetics of nonylphenol. Cell growth and nonylphenol removal date were collectedusing batch reactors of each initial nonylphenol density, respectively. It was shownthat biodegradation of nonylphenol was a substrate-inhibited process. Cell growthand nonylphenol removal were modeled by Haldane, Webb, Aiba, Yano and Tessiserequations. The results showed that Aiba, Haldane model providing the best fit, and can be used to describe the growth kinetics of the pure and mixed bacteria in thedegradation of nonylphenol.By means of LC-MS, we analzed the possible ways of biodegradation ofnonylphenol was the conversion of the alkyl chain into the corresponding alcoholby an ipso-substitution mechanism, and the alkylic intermediate reacted with waterto from nonanol. Also found that1-methylcyclohexa-3,5-diene-1,2,4-triolcompound with2,5,5-trimethylheptane was the intermediate product ofRhodotorula sp. biodegradation of nonylphenol.Bioremediation of the contaminated soil has become a focus in the field ofenvironmental protection. We also studied the bioremediation of thenonylphenol-contaminationed soil by the Rhodotorula sp. in laboratory. At thedensity of nonylphenol (11mg/kg dry soil), adding the Rhodotorula sp. increasedthe degradation rate of nonylphenol, decreasiong the half life time of nonylphenolpollutant in the soil from33.3d to2.07d, but in the higher desity pollutant(44mg/kg dry soil), the substrate-inhibited effect became dominant and thenonylphenol degradation rate decreased obviously. Therefore, the Rhodotorula sp.is applicable to the bioremediation of polluted soil of low and mediumconcentration.As the results of this study, Candida tropicalis, Rhodotorula sp., Trichosporonsp. could degrade nonylphenol. Rhodotorula sp. is environment-friendlymicroorganisms, has the application potential in the bioremediation ofcontaminated soil by nonylphenol.