Arzu Ünal

Reaction kinetics for laccase-catalyzed polymerization of 1-naphthol.

Laccase-catalyzed oxidative polymerization of 1-naphthol was carried out in a closed system containing acetone and sodium acetate buffer. The effects of initial 1-naphthol and dissolved oxygen concentrations on the initial reaction rate were investigated. A multiplicative mathematical model, using a function of 1-naphthol and dissolved oxygen concentrations, was developed for enzymatic polymerization and the corresponding biokinetic parameters have been evaluated for the first time. The activation energy and reaction rate constant of the laccase-catalyzed 1-naphthol polymerization were calculated as 57 kJ/mol and 311 l/s, respectively. The activation energy calculated was in the typical range of 30-60 kJ/mol and rate constant was of the order of magnitude of previously reported values for laccase-catalyzed reactions with different monomers.

New fungal biomasses for cyanide biodegradation

Cyanide, a hazardous substance, is released into the environment as a result of natural processes of various industrial activities which is a toxic pollutant according to Environmental Protection Agency. In nature, some microorganisms are responsible for the degradation of cyanide, but there is only limited information about the degradation characteristics of Basidiomycetes for cyanide. The aim of the present study is to determine cyanide degradation characteristics in some Basidiomycetes strains including Polyporus arcularius (T 438), Schizophyllum commune (T 701), Clavariadelphus truncatus (T 192), Pleurotus eryngii (M 102), Ganoderma applanatum (M 105), Trametes versicolor (D 22), Cerrena unicolor (D 30), Schizophyllum commune (D 35) and Ganoderma lucidum (D 33). The cyanide degradation activities of P. arcularius S. commune and G. lucidum were found to be more than that of the other fungi examined. The parameters including incubation time, amount of biomass, initial cyanide concentration, temperature, pH and agitation rate were optimized for the selected three potential fungal strains. The maximum cyanide degradation was obtained after 48 h of incubation at 30°C by P. arcularius (T 438). The optimum pH and agitation rate were measured as 10.5 and 150 rev/min, respectively. The amount of biomass was found as 3.0 g for the maximum cyanide biodegradation with an initial cyanide concentration of 100mg/L. In this study, agar was chosen entrapment agent for the immobilization of effective biomass. We suggested that P. arcularius (T 438) could be effective in the treatment of contaminated sites with cyanide due to capability of degrading cyanide.