Degradation of triphenylmethane dyes using a temperature and pH stable spore laccase from a novel strain of Bacillus vallismortis

The characterization of a spore laccase from Bacillus vallismortis fmb-103, isolated from textile industry disposal sites, is described. The activity was 6.5 U/g of dry spore with ABTS as the substrate. The enzyme was quite stable at high temperature. It retained more than 90% of its initial activity after 10 h at 70 °C. The enzyme demonstrated broad pH stability in both acidic and alkaline conditions. There was almost no activity loss at pH 3 over an extended period of time, and the relative activity remained at 82% and 38% at pH 7 and pH 9 after 10 days. NaN3, SDS, l-cysterine, Dithiothreitol, EDTA and NaCl inhibit the enzyme activity. Triphenylmethane dyes, including malachite green, brilliant green and aniline blue were efficiently degraded by the enzyme after 24 h in combination with a mediator with efficiencies of 76.84%, 96.56% and 81.17%, respectively. The reusability of spore laccase for decolorization dyes was also examined.

► The strain fmb-103 producing spore laccase is identified as Bacillus vallismortis. ► The spore laccase from strain fmb-103 is stable at high temperature. ► The spore laccase from strain fmb-103 is stable both at acidic and alkaline pH. ► The spore laccase can efficiently degrade triphenylmethane dyes.