Optimisation of Fungal Laccase Production from Monodictys castaneae

Abstract

Laccases are copper-containing oxidase enzymes that have broad substrate specificity and applicability in industrial processes. The purpose of this work was to optimise laccase production by a certain endophytic fungus. Monodictys castaneae (Wallr.) Hughes was cultured and incubated using different nutritional and physiological factors affecting laccase production. It was found that the optimum physiological conditions for laccase production were 4 disc inoculum size, a 9-day fermentation period, pH 5, and 28°C. The enzyme was purified using acetone precipitation, gel filtration, and ion-exchange chromatography. The enzyme was identified as a monomeric protein with a molecular mass of 63 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Different concentrations of CuSO4 were used to stimulate laccase production and activity. A 0.15 g/l concentration of CuSO4 was the optimum dosage for laccase activity enhancement. For enzyme-guaiacol interaction, the optimal pH and temperature were 5.4 and 35 °C, respectively. The laccase activity was highly stimulated using 3 mM and 7 mM concentrations of chloride salts of Cd+2, Ca+2, Cr+2 and Fe+3, but the enzyme activity was slightly inhibited by 10 mM concentrations of these metal ions. According to all previous results, Monodictys castaneae showed promising potential as a producer of laccase.