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The Oxidation Effect Of Serratia Marcescens AB90027 And Its Enzyme On Aromatic Compounds

Posted on:2007-12-10Degree:MasterType:Thesis
Country:ChinaCandidate:M SunFull Text:PDF
GTID:2121360182986638Subject:Applied Chemistry
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This thesis researches on the oxidation effect of aromatic compounds by the bacterium Serratia marcescens AB90027 and its enzyme. The research consists of two main parts: Firstly, a crude enzyme extract was used to transform isoeugenol to vanillin, and the transformation pathway was investigated. Then, the oxidation effect of AB90027 and its enzyme on phenols and anilines was studied. The degrading mechanism, kinetic condition and characteristic of enzyme were estimated. The work was composed of four parts:(1) A crude enzyme from AB90027 was used to catalyze to produce vanillin from isoeugenol. The transformation pathway of isoeugenol was studied by TLC, UV-visible spectrum and IR spectrum. The yields of vanillin in different reaction system were measured by TLCS. The situation of the enzyme which could catalyze to synthesize vanillin was studied. The results showed that during the transformation process, isoeugenol broke its phenyl ring and became to small molecules with ferulic acid and vanillin as intermediates respectively, the highest yield of product vanillin could be 10.90% when catalyzed just by enzyme. The enzyme which had ability to catalyze isoeugenol converting to vanillin was mainly extracellular enzyme.(2) 15 kinds of phenols and anilines were degraded using hydrogen peroxide as oxidizer and enzyme from Serratia marcescens AB90027 as catalyst. Hydroquinone and p-aminophenol were chosen for studying the kinetic conditions. The results showed in the degradation of hydroquinone(2000 mg L-1, 50 mL), the optimal volume of H2O2(30%, w/v), temperature and pH were 5 mL, 40℃ and 9.5, respectively. And the COD removal efficiency could get to 96.3% after treated for 24 h. For P-aminophenol(500 mg L-1, 50 mL), the optimal conditions were, the volume of H2O2(30%, w/v) was 3 mL, the temperature was 40℃60℃ and the pH was 9~10. After treatment the COD removal efficiency was up to 96.80%. The COD of these 15 kinds of compounds before and after treatment were measured, and changes of molecular structures during the process were investigated by UV-VIS, IR and HPLC. It was found that after H2O2/enzyme treatment, to some compounds such as hydroquinone, peaks on UV-VIS and IR spectra which belong to phenyl ring all disappeared, and HPLC discovered small molecules such as organic acids. So the mechanism was clarified that during the degradation the phenyl ring was cleaved and small molecules were introduced, which just caused the COD values ofdegradation-amiable compounds such as hydroquinone declined greatly. Also, the relation between degradability and structure of phenols and anilines was analyzed, and the conclusion was as follows: di-/tri-phenols/anilines were easier to degrade than mono-phenols/anilines;ortho-/para- substituted compounds were easier to degrade than meta- substituted compounds;electron-donating substituents such as -OH, -NH2 and -OCH3 made degradation easier, while electron-withdrawing substituents such as -NO2, -Cl and -COOH made degradation more difficult. The t^Ch/enzyme treatment was also applied to treat industrial hydroquinone effluents and the efficiency was estimated.(3) Cometabolism-H2O2 oxidation method was applied to degrade degradation-resistant compounds such as phenol, resorcinol and salicylic acid, and it was proved as a process of phenyl rings cleavage as well.(4) The fermentation conditions such as time, temperature, pH and shaking speed were discussed and the characteristic of enzyme was investigated. The optimal fermentation conditions of the enzyme were as follows: fermentation period 30 h, temperature 28°C, initial pHlO.O, shaking speed 150r min'1. The enzyme was mainly extracellular enzyme, whose catalyzing mechanism was presumed to strengthen the oxidizing behavior of H2O2.
Keywords/Search Tags:Serratia marcescens, enzyme, hydrogen peroxide, catalyze, vanillin, isoeugenol, degrade, phenol, aniline, cleavage, cometabolism
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