THE BIOLOGICAL DECOMPOSITION OF PLANT NATERIALS: PART IX. THE AEROBIC DECOMPOSITION OF HEMICELLULOSES

Abstract

SUMMARY.1. The decomposition of the hemicelluloses of plant materials occurs rapidly under normal aerobic conditions. Since a number of fungi have been shown by analyses of pure culture rots to be active in fermenting this group, as well as cellulose, some seventy common fungi, mostly Aspergilli and Penicillia, were tested as to their ability to utilise on agar plates the crude hemicellulose from oat straw.2. All of the fungi tested grew reasonably well on the hemicellulose medium, the majority at least as well as on glucose, and a number better than on that sugar. In some cases there was production of a cleared zone round the colony due to an exo‐enzyme. It is likely that ability to ferment hemicelluloses will be found to be a general property of common fungi.3. From soil, manure, and straw, twenty aerobic bacteria were isolated capable of utilising hemicelluloses. Three of these were thermophilic forms. Their morphological characters and biochemical reactions were determined.4. All the organisms utilised a very wide range of sugars and poly‐saccharides; one group produced some acid and gas, the remainder little. Differentiation was obtained on saccharic acid and certain disaccharide acids.5. Five of the mesophilic organisms agreed closely with the description of Achromobacter ubiquitum (Jordan). The remainder were aerobic spore‐formers, though not all Gram‐positive. The negative forms may represent new species.6. None of the organisms in pure culture could validly be described as active in decomposing the isolated hemicellulose, or that in situ in straw.7. Fungi seem to be more active and important in the natural decomposition of hemicelluloses than bacteria, unless when working in association the rather restricted individual fermentative powers of the latter are considerably enhanced.