Lignin Degradation by Streptomyces viridosporus : Isolation and Characterization of a New Polymeric Lignin Degradation Intermediate

Abstract

A new, quantitatively significant intermediate formed during lignin degradation by Streptomyces viridosporus T7A was isolated and characterized. In Streptomyces-inoculated cultures, the intermediate, an acid-precipitable, polyphenolic, polymeric lignin (APPL), accumulated in the growth medium. The APPL was a water-soluble polymer probably consisting of a heterogeneous mixture of molecular weight components of .20,000. APPLs were precipitable from culture filtrates after they had been acidified to pH <3 to 5. Noninoculated controls yielded little APPL, but supernatant solutions from inoculated cultures produced quantities of APPL that correlated with the biodegradability of the lignocellulose type. Maximal recovery of APPL was obtained from corn lignocellulose, reaching 30% of the initial lignin present in the substrate. APPLs contained small amounts of carbohydrate, organic nitrogen, and inorganic materials. The lignin origin of APPLs was confirmed by chemical analyses, which included acidolysis, permanganate oxidation, elemental analyses, functional group analyses, nuclear magnetic resonance spectroscopy, and 14C isotopic techniques. Analyses of APPLs from corn lignocelluloses showed that S. viridosporus-degraded APPLs were lignin derived but significantly different in structure from APPLs derived from uninoculated controls or from a standard corn milled-wood lignin. Degraded APPLs were enriched in phenolic hydroxyl groups and, to a small extent, in carboxyl groups. Degradative changes appeared to be largely oxidative and were thought to involve substantial cleavage of p-hydroxy ether linkages and methoxyl groups in the lignin.

Isolation and identification of cellulolytic bacteria from gastrointestinal tract of Arabian horse and investigation of their effect on the nutritional value of wheat straw

“…Decrease in NDF, iNDF and ADF contents in WS by bacterial treatments was similar to the study by Crawford (1978) who reported that the selected strains of Streptomyces degraded 25-40% of cellulose content of lignocellulose after 6 weeks of incubation. Additionally, in the work of Crawford et al (1983), carbohydrate content of corn stem decreased 44Á4% after 8 weeks of incubation with Streptomyces viridosporus. Kerr and Kerr (1987) also degraded 6Á5% of grass polysaccharides after 10 days of incubation with Arthrobacter.…”

Lignocellulose-degrading actinomycetes

“…Subsequently, attention has focussed on analysis of the products of actinomycete attack in an effort to gain insight into the mechanism of degradation. Some low molecular weight products such as syringic and ferulic acids have been detected [113] but the major product is a high molecular weight complex of lignin, carbohydrate and protein [49,114,115]. Grass lignocelluloses are much more susceptible to actinomycete attack than those of wood [113,114], as indicated by the yields of this water-soluble, acid-precipitable material (APPL) from culture filtrates.…”

“…Some low molecular weight products such as syringic and ferulic acids have been detected [113] but the major product is a high molecular weight complex of lignin, carbohydrate and protein [49,114,115]. Grass lignocelluloses are much more susceptible to actinomycete attack than those of wood [113,114], as indicated by the yields of this water-soluble, acid-precipitable material (APPL) from culture filtrates. Using ~4C-labelled wheat lignocellulose, McCarthy and Broda [17] found that solubilisation of radiolabelled material (30-40%) occurred during primary growth with no evidence of further significant degradation or mineralisation to CO 2 by fresh cultures of Thin.…”

Dissolved organic matter and its parent organic matter in grass upland soil horizons studied by analytical pyrolysis techniques

“…Lignin degradation products in DOM are almost entirely polymeric, although they are smaller and more polar than lignin itself, because of oxidative degradation (Zech et al, 1992). Crawford et al (1983) showed experimentally that oligomeric structures and water-soluble polymeric materials are formed during fungal decay of lignin. Lignin-type polymeric structures have been found in DOM samples from rivers and lakes (Ertel et al, 1984), and from forest soil leachates (Guggenberger & Zech, 1994).…”