Acid-precipitable polymeric lignin: Production and analysis

Abstract

This chapter describes the procedures for growing two distinctly different lignin-degrading Streptomyces under conditions optimal for lignocelluloses degradation and acid-precipitable polymeric lignin (APPL) production by each. One species, S. viridosporus, is grown in solid-state fermentations, and the second, S.badius, is grown in submerged cultures after preincubation for a period of time as a solid-state fermentation. Direct mycelial contact with the substrate is required for growth of both of these Streptomyees on lignocellulose. Also, the procedures for harvesting and chemically characterizing residual partially degraded lignocelluloses and the APPLs produced as a result of lignin depolymerization are described in the chapter. After their harvest by aqueous extraction from partially decomposed lignocellulosic residues, the APPLs and the residual insoluble lignocelluloses are analyzed for their Klason lignin, carbohydrate, protein, and ash contents. The APPLs are further characterized chemically by degradative procedures including acidolysis, permanganate oxidation, and alkaline ester hydrolysis. These procedures break the APPL down to the level of single-ring aromatics that can be analyzed by gas-liquid chromatography. When native lignin is used as a comparative control, these analyses allow one to elucidate some of the key chemical changes occurring in lignin as a result of its degradation by ligninolytic microorganisms.