Recovery and analysis of solubilised brown coal from cultures of wood-rot fungi

J. P. Ralph, D. E.A. Catcheside

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    The effectiveness of alkali-washing as a method for recovering fractions of brown coal soluble in alkali (AS-coal) from cultures of brown and white-rot fungi was investigated. AS-coal was found to precipitate in fungal growth medium, causing an increase in modal apparent molecular mass (MAM(r)), and to bind to medium components and fungal mycelia. In consequence, fungal-mediated degradation of AS-coal cannot be determined by direct analysis of AS-coal present in culture fluid. Total recovery of AS-coal was achieved by (i) acidifying cultures and pelleting fungal mycelia and AS-coal by centrifugation, (ii) incubating AS-coal and mycelia in NaOH to resolubilise the AS-coal, (iii) separating AS-coal from mycelia by filtration, (iv) re-precipitation of AS-coal with acid and (iv) resuspending the AS-coal in phosphate buffer for analysis. Fourier transform infrared spectroscopy showed this process to remove all contaminants derived from growth medium except oleic acid and Tween-80. These compounds do not change the absorbance or MAM(r) of AS-coal as determined by size exclusion chromatography (SEC). The presence of 100 mM ortho phosphate, pH 6.9, had a differential effect on the MAM(r) of AS-coal depending upon the pH used for its initial solubilisation. Coal fractions soluble below pH 4.5 had a lower MAM(r) in phosphate than in water. In contrast, a coal fraction solubilised between pH 4.5 and 6 had an increased MAM(r) in phosphate buffer. These effects are probably due to changes in the hydrodynamic volume of coal macromolecules, making SEC appropriate for determining relative but not absolute changes in the M(r) of solubilised coal.

    Original languageEnglish
    Pages (from-to)1-11
    Number of pages11
    JournalJournal of Microbiological Methods
    Issue number1
    Publication statusPublished - Sept 1996


    • Biodegradation
    • Lignite
    • Phanerochaete chrysosporium
    • Size exclusion chromatography
    • Solubilisation
    • Whiterot fungi


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