Extracellular Alkaline Thermostable Laccase from Micrococcus species: Partial Purification and Characterization
Babu Joseph, Mohammed Kuddus and Pramod W. Ramteke
Affiliation: College of Applied Medical Sciences, Shaqra University, Kingdom of Saudi Arabia.
A bacterial strain producing extracellular alkaline thermostable laccase has been isolated from sawdust
effluents and identified as Micrococcus species. The laccase was partially purified and characterized. The isolate showed
maximum laccase production after 120 h, at 30ºC with an optimum pH of 9.0. The specific activity was 127.94 U/mg with
a purification fold of 5.54 was obtained with DEAE-cellulose anion exchange chromatography. The molecular weight of
purified laccase was 23 kDa. A temperature of 40ºC and pH of 9.0 was found to be optimum for laccase activity. Laccase
was stable at 50ºC and at a pH of 9.0 after 1 h incubation. Laccase retained 70-80% of its activity in the presence of 5%
DMSO, butanol, acetone and isopropanol. The laccase activity was inhibited by 10 mM SDS (90%), mercuric chloride
(80%) and p-CMB (80%). However, only 30% of the enzyme activity was inhibited by sodium azide and EDTA. The
characteristics of partially purified laccase with respect to inhibitors and metal ions contribute towards the understanding
for the use of bacterial laccases for industrial applications.
Keywords: ABTS, alkaline, laccase, Micrococcus, thermo-stable.
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