Enhanced degradation of lignosulfonated compounds by Streptomyces viridosporus

Degradation of lignosulfonated compounds by S. viridosporus strain T7A on nutritive or mineral culture media was quantified. Two lignosulfonated compounds, differing in their molecular mass distributions and chemical structures, were used: lignosulfonate (1–80 kDa) and vanisperse, a sulfonated oxylignin (1–20 kDa). The use of nutritive culture medium (containing Biosoyase) enhanced both the growth of S. viridosporus and production of lignin peroxidase (LiP) leading to enhanced lignocellulose degradation, but no lignosulfonated compound degradation was observed. A fraction of these compounds underwent a molecular transformation, producing non-biodegradable acid precipitable polymeric lignin (APPL). When a mineral culture medium (containing glycerol as additional organic carbon source) was used, approximately 21 and 35% of lignosulfonate and vanisperse were respectively degraded, with little APPL production. LiP activity was growth-associated and significant modifications of molecular mass distributions of both lignosulfonated compounds were observed. A mixed natural microbial population, collected in an aerated lagoon treating Fluff pulp effluent, was used to evaluate the biodegradability of lignosulfonate products from S. viridosporus cultures. This population was (i) unable to degrade lignosulfonate products, and (ii) decreased the lignosulfonate degradation capacity of S. viridosporus. Antagonistic effects of the mixed population on S. viridosporus were observed. In the light of this, bioaugmentation strategies involving addition of S. viridosporus are unlikely to be successful and alternative degradation strategies need to be developed.