Acid-precipitable polymeric lignin

Two Streptomyces strains, S. badius and S. viridosporus, were found to be able to grow on kraft lignin (In-dulin ATR) as sole carbon source. The resulting APPL (Acid Precipitable Polymeric Lignin) was characterized by FTIR and elemental analysis for C, H and N, and was found to contain proteins in addition to a relatively demethoxylated lignin component. The proteins were further characterized by amino acid analysis, while the lignin component was separated by solvent extraction and its molecular weight distribution determined by HPSEC. 

Crawford and co-workers were the first to study in detail the action of two streptomyces, S. badius 252 and S. viridosporus T7A, on lignocellulose from different sources. Their work led to the conclusion that the bacterial action on aqueous suspensions of these lignocellulosics resulted in the solubilization of lignin fragments which precipitate upon acidification Acid Precipitable Polymeric Lignin (APPL) (1-10). 

Soil organic matter (SOM) is often referred to as humus and is derived primarily from the degradation of plant material lignin, carbohydrates, protein, fats, and waxes. Mineral soils may contain 0.5-3.0% of soil organic matter while muck soils and peat contain 50% and higher. Operationally, the material that cannot be extracted by alkaline agents is called humin. The material that precipitates from the alkaline extract on acidification is called humic acid, and what remains in solution fulvic acid. Felback summarized some of the properties of these complex polymeric materials as follows ... 

Hydrolysis reactions were carried out in methanol solution in the presence of NaOH (1 mmol/g polymer) at 40 °C. The reaction mixture was neutralized with acetic acid and the resulting polymeric material was purified by two precipitations in acetone. The amount of lignin in the... 

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