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Appl. Environ. Microbiol., Jun 1996, 1928-1934, Vol 62, No. 6
Copyright © 1996, American Society for Microbiology

Analysis of Lignin-Polysaccharide Complexes Formed during Grass Lignin Degradation by Cultures of Pleurotus Species

A Gutierrez, P Bocchini, GC Galletti and AT Martinez
Centro de Investigaciones Biologicas, Consejo Superior de Investigaciones Cientiificas, E-28006 Madrid, Spain, and Centro di Studio per la Conservazione dei Foraggi, Consiglio Nazionale delle Ricerche, I-40126 Bologna, Italy

A brown material, precipitable with ethanol, was formed during wheat straw and lignin degradation by liquid cultures of different species of Pleurotus. Fourier transform infrared spectroscopy and cross-polarization and magic-angle-spinning (sup13)C nuclear magnetic resonance spectroscopy showed that most of the precipitable material was formed from exopolysaccharide secreted by the fungus but it also contained an aromatic fraction. The results of acid hydrolysis, methylation analysis, and Smith degradation indicated that the major exopolysaccharide produced by these fungi is a (1(symbl)3)-(beta)-glucan branched at C-6 every two or three residues along the main chain. The presence of lignin or straw in the culture medium had little effect on the composition and structure of the extracellular polysaccharide. Cross-polarization and magic-angle-spinning (sup13)C nuclear magnetic resonance spectroscopy provided an estimation of the aromatic content of the lignin-polysaccharide complexes, assigning 20% of the total (sup13)C signal in the material recovered from cultures of Pleurotus eryngii in lignin medium to aromatic carbon. Analytical pyrolysis indicated that the aromatic fractions of the lignin-polysaccharide complexes were derived from lignin, since products characteristic of pyrolytic breakdown of H (p-hydroxyphenylpropane), G (guaiacylpropane), and S (syringylpropane) lignin units were identified. These complexes cannot be fractionated by treatment with polyvinylpyrrolidone or extraction with lignin solvents, suggesting that the two polymers were chemically linked. Moreover, differences in composition with respect to the original lignin indicated that this macromolecule was modified by the fungi during the process of formation of the lignin-polysaccharide complexes.


This article has been cited by other articles:

  • Barrasa, J. M., Gutiérrez, A., Escaso, V., Guillén, F., Martínez, M. J., Martínez, A. T. (1998). Electron and Fluorescence Microscopy of Extracellular Glucan and Aryl-Alcohol Oxidase during Wheat-Straw Degradation by Pleurotus eryngii. Appl. Environ. Microbiol. 64: 325-332 [Abstract] [Full Text]  


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