Selection and Efficiency of Lignin Degradation by Bacteria Isolated from Wastewater in the Pulp and Paper Industry

The aims of this research were to isolate lignin-degrading bacteria from wastewater in the pulp and paper industry and to study lignin degradation efficiency of selected bacteria in the synthetic lignin wastewater. Thirty bacterial isolates (VP1-VP30) obtained by randomly colonial selection were primarily tested for lignin peroxidase enzyme production on minimal salt medium (MSM) containing 0.25 g/L methylene blue.  As a result, 14 isolates could generate the varying clear zone with the largest size of 4.0 millimeters. Among these isolates, VP13 VP16 VP19 and VP23 isolates showed the increasing clear zone from 2.0-3.0 millimeters (day 5) to 3.0-4.0 millimeters (day 7); and all of them were gram positive bacteria with rod-shape. Thus, these 4 isolates together with Bacillus subtilis laboratory strain were selected for further testing lignin degradation efficiency using synthetic lignin wastewater. The results found that the VP16 isolate could more efficiently decolorize lignin presented in synthetic lignin wastewater after incubating 15 days by observing the physical color appearance, and it showed efficient degradation of lignin by giving removal efficiency of 41.20%, which was 1.4-2.6 times higher than that from other isolates and B. subtilis by measuring concentration of lignin at OD 280 . In addition, VP16 isolate had the highest removal efficiency of 33.33% for reducing COD in synthetic lignin wastewater tested by close reflux method; meanwhile, the removal efficiency of 15.39% was observed from B. subtilis. Keywords: wastewater in the pulp and paper industry; lignin; lignin-degrading bacteria; lignin peroxidase