Isolation of a lignin-decolorizing bacterium

Abstract

A bacterial strain, that degraded and decolorized lignin very rapidly, was isolated from soil and identified as Azotobacter sp. HM121. The optimal culture conditions were determined to be in a medium containing 0.4 g/ l lignin, 5.0 g/ l glycerol, 0.2 g/ l ammonium sulfate, 0.2 g/ l manganese sulfate tetrahydrate, 0.2 g/ l magnesium sulfate heptahydrate, 1.0 g/ l potassium dihydrogen phosphate, 0.2 g/ l Polypepton, and 0.2 g/ l yeast extract, pH 6.0, with incubation for 2 d at 30°C. In repeated batch culture, the strain degraded and decolorized lignin in 1 d and the system was stable for at least 12 d. The strain could degrade most types of lignin with the exception of soft wood kraft lignin, but did not work well for the bleaching of pulp.