title: Water purification through bioconversion of phenol compounds by tyrosinase and chemical adsorption by chitosan beads.
abstract: Enzymatic removal of various phenol compounds from artificial wastewater was undertaken by the combined use of mushroom tyrosinase (EC 1.14.18.1) and chitosan beads as function of pH value, temperature, tyrosinase dose, and hydrogen peroxide-to-substrate ratio. Chitosan film incubated in a p-crersol+tyrosinase mixture had the main peaks at 400-470 nm assigned to chemically adsorbed quinone derivatives, which increased over the immersion time. These results indicate that removal of phenol compounds is caused by their tyrosinase-catalyzed oxidation to the corresponding quinone derivatives and the subsequent chemical adsorption on the chitosan film. The optimum conditions for quinone adsorption were determined to be pH 7 and 45 degrees C for p-cresol. Some alkyl-substituted phenol compounds were removed by adsorption of quinone derivatives enzymatically generated on the chitosan beads, and the % removal for p-cresol, 4-ethylphenol, 4-n-propylphenol, 4-n-butylphenol, and p-chlorophenol went up to 93%. In addition, 4-tert-butylphenol underwent tyrosinase-catalyzed oxidation in the presence of hydrogen peroxide. This procedure was applicable to removal of chlorophenols and alkyl-substituted phenols.
authors.affiliation: Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, 1-2-1 Izumi-cho, Narashino, Chiba 275-8575, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yamada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Akiba
authors.forename: Takashi
authors.initials: T
authors.lastname: Shibuya
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kashiwada
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Matsuda
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Hirata
mesh_terms: D000327:Adsorption; D000363:Agaricales / Q000201:enzymology; D001673:Biodegradation, Environmental; D048271:Chitosan / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008863:Microspheres; D014442:Monophenol Monooxygenase / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry* / Q000302:isolation & purification*; D011485:Protein Binding; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods*
chemical_list: D020099:Coated Materials, Biocompatible; D004800:Enzymes, Immobilized; D010636:Phenols; D014874:Water Pollutants, Chemical; D048271:Chitosan; D014442:Monophenol Monooxygenase