Optimization and characterization of lignosulfonate biodegradation process by a bacterial strain, Sphingobacterium sp. HY-H

The objective of this study was to investigate the optimization and pathways of lignosulfonate biodegradation by a newly isolated lignin-degrading bacterial strain, Sphingobacterium sp. HY-H. The optimal conditions for lignosulfonate degradation capability were determined by Taguchi's orthogonal matrix method to be: initial pH, 7.0; temperature, 30°C; and a lignosulfonate/nitrogen (as NH₄Cl) mass ratio of 5. Under optimal conditions, the maximum lignosulfonate degradation capacity of strain HY-H was 31%. In order to characterize the changes in residual lignosulfonate and the metabolic products, FTIR spectra, functional groups, and elemental and GC-MS analysis were introduced. An examination of the data suggests a possible route of lignosulfonate degradation by strain HY-H was that lignosulfonate was first depolymerized to low-molecular-weight compounds; then the side chains of lignosulfonate were partially oxidized and further decarboxylated to produce carbon dioxide. If properly optimized and controlled, strain HY-H may play a role in the treatment of pulp and paper wastewater containing a high concentration of lignosulfonate, as well as in the lignocellulose breakdown for biofuel and chemicals production.