Degradation and Utilization of Isolated Hemicellulose by Pure Cultures of Cellulolytic Rumen Bacteria

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Abstract
Hemicelluloses isolated from flax, corn hulls, alfalfa, oat hulls, and fescue grass were used as sole energy sources to study the ability of pure cultures of cellulolytic rumen bacteria to degrade and utilize these materials. From a total of eight bacterial strains tested (three strains of Bacteriodes succinogenes, four strains of Ruminococcus flavefaciens, and one strain of R. albus), only three strains of ruminococci were able to utilize the hemicelluloses for growth. Hemicellulose fermentation mixtures were analyzed for total pentose, residual hemicellulose (pentose precipitated in 80% ethyl alcohol), and ethyl alcohol-soluble pentose. The three strains of ruminococci were able to partially utilize the different hemicelluloses as energy sources, as determined by total pentose loss, and they were capable of almost complete degradation of the original hemicellulose from an ethyl alcohol-insoluble to ethyl alcohol-soluble form. The extent of both degradation and utilization varied markedly between the three strains and different substrates. Tests on the other strains indicated that no growth, production of organic acid end products, or appreciable loss of total pentose had occurred. However, analysis of the culture medium for residual hemicellulose indicated that these strains were able to extensively degrade the original hemicelluloses to an ethyl alcohol-soluble form. Marked differences were observed among strains and hemicelluloses in the amount of hemicellulose degraded. Of the different hemicelluloses, corn-hull hemicellulose was the most resistant to degradation and utilization by the cellulolytic rumen bacteria.