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Abstract
A sedimentation chamber and Andersen sampler were used to isolate a range of actinomycetes on selective and non-selective media. The occurrence of different actinomycete groups in natural substrates was compared and strains were screened for the ability to degrade ball-milled straw or to grow on lignin-related phenolic compounds. Evidence for ligninolytic activity in representatives of several genera was obtained by assaying 14CO2 evolution from [14C]lignin-labelled wheat lignocellulose. Most of the straw-degrading isolates were assigned to the genera Thermomonospora and Micromonospora, but only representatives of the latter were found to be active against [14C]lignin. Of the non-straw-degrading strains also examined, some which could utilize phenolic substrates produced 14CO2 from the [lignin-14C]lignocellulose, and two of these were selected for further study. These strains, Thermomonospora mesophila and a Streptomyces sp., attacked [14C]lignin yielding 14CO2 and water-soluble 14C-labelled compounds during primary growth. This activity was not accounted for by the utilization of phenolic acids linked to the carbohydrate fraction of wheat lignocellulose and was unaffected by cultural parameters known to influence lignin degradation by white-rot fungi.
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