CHARACTERIZATION OF LACCASE ACTIVITY PRODUCED BY Cryptococcus albidus

Abstract

This study deals with the characterization of laccase enzyme activity produced by Cryptococcus albidus. Industrial wastes like effluent and sludge are complex mixtures of a number of chemicals. These chemicals can interfere with the proper functioning of the enzymes used for bioremediation. Thus, it is important to study the effect of such interfering solvents, detergents, metal chelators, and other chemicals on enzyme activity before industrial applications. Laccase showed maximum activity at pH 2.5 and temperature 20–30°C when ABTS was used as a substrate. The enzyme followed Michaelis–Menten kinetics: K_m was 0.8158 mM and V_max was 1527.74 U/mg. Laccase showed good thermostability with a half-life of 81 min at 25°C, 77 min at 35°C, 64 min at 45°C, 36 min at 55°C, and 21 min at 65°C. There was no effect of sodium dodceyl sulfate (SDS) (0.1–1.0%) and EDTA (0.1–0.5%) on laccase activity. Sodium azide and 2-mercaptoethanol showed complete inhibition of laccase activity at 0.1% concentration. At lower concentrations of acetone and acetonitrile, laccase was able to maintain its activity. However, the activity was completely inhibited at a concentration of 50% or above of acetone, methanol, 1,4-dioxan, and acetonitrile.

Keywords:

• Cryptococcus albidus
• characterization
• half-life
• kinetics
• laccase
• solvent

ACKNOWLEDGMENTS

The authors thank the University Grants Commission (UGC), New Delhi, India, for providing a Senior Research Fellowship to Anjali Singhal and for financial support. The authors are grateful to Department of Biotechnology, Government of India, New Delhi, for financial support in the form of projects.