An acid-stable bacterial laccase identified from the endophyte Pantoea ananatis Sd-1 genome exhibiting lignin degradation and dye decolorization abilities.

Abstract

Isolation and identification of a novel laccase (namely Lac4) with various industrial applications potentials from an endophytical bacterium. Endophyte Sd-1 cultured in rice straw showed intra- and extra-cellular laccase activities. Genomic analysis of Sd-1 identified four putative laccases, Lac1 to Lac4. However, only Lac4 contains the complete signature sequence of laccase and shares at most 64% sequence identity with other characterized bacterial multi-copper oxidases. Recombinant Lac4 can oxidize non-phenolic and phenolic compounds under acidic conditions and at 30-50°C; Km values of Lac4 for ABTS at pH 2.5 and for guaiacol at pH 4.5 were 1±0.15 and 6.1±1.7mM, respectively. The activity of Lac4 was stimulated by 0.8mM Cu(2+) and 5mM Fe(2+). In addition, Lac4 could decolorize various synthetic dyes and exhibit the degradation rate of 38% for lignin. The data suggest that Lac4 possesses promising biotechnological potentials.