title: Removal of naphthols and analogues by the combined use of an oxidoreductase polyphenol oxidase and a biopolymer chitosan from aqueous solutions.
abstract: In this study, the combined use of an amino group-containing polymer chitosan and an oxidoreductase polyphenol oxidase (PPO) was applied to the removal of naphthols and dihydroxynaphthalenes (DHNs) from aqueous solutions. The process parameters, such as the pH value, temperature and enzyme dose, were discussed for PPO-catalysed oxidation of 1-naphthol. The optimum conditions of enzymatic oxidation of 1-naphthol were determined to be pH 8.0 and 40 °C. Under the optimum conditions, PPO-catalysed oxidation of 1-naphthol increased with an increase in the enzyme dose. Quinone derivatives enzymatically generated were chemisorbed on chitosan beads and the initial velocity of PPO-catalysed oxidation increased with an increase in the amount of added chitosan beads. A specific initial velocity of 0.0675 μmol/U·min was obtained in the PPO concentration range below 200 U/cm³ and 1-naphthol was completely removed within 24 h by quinone adsorption on chitosan beads (0.20 cm³/cm³) at a PPO concentration of 100 U/cm³. The removal time was shortened by increasing the enzyme dose or the amount of added chitosan beads. 2-Naphthol was also completely removed at an initial concentration of 0.05 mM or less by prolonging the reaction time, since PPO-catalysed oxidation of 2-naphthol was much slower than that of 1-naphthol. In addition, this procedure was also applied to the removal of DHNs. These results revealed that the procedure constructed in this study was an effective technique to remove naphthols and DHNs from the aqueous medium.
authors.affiliation: a Department of Applied Molecular Chemistry , College of Industrial Technology, Nihon University , 1-2-1 Izumi-cho, Narashino , Chiba 275-8575 , Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kimura
authors.forename: Asahi
authors.initials: A
authors.lastname: Gotoh
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Shinozaki
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kashiwada
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yamada
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009284:Naphthols / Q000737:chemistry*; D010084:Oxidation-Reduction; D012996:Solutions; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification
chemical_list: D009284:Naphthols; D012996:Solutions; D014874:Water Pollutants, Chemical; D048271:Chitosan; D004156:Catechol Oxidase
keywords: chitosan; dihydroxynaphthalene; naphthol; polyphenol oxidase; water purification