The Effects of Physical and Chemical Properties of Cellulosic Fibers on Anaerobic Deterioration by Pure Cultures

Abstract

Decomposition of cellulosic fibers by thirteen strains including three species of the obligately anaerobic genus Ruminococcus has been investigated with regard to the effects of the chemical composition and physical state of the fiber. Of the thirteen strains only six were actively cellulolytic. In test systems containing 50 mg of fiber in 10 ml of medium, nearly complete solubilization of substrate was observed in 11 to 14 days. The substrates were jute, cotton, alfalfa, filter paper, and varous materials derived from these. As with other cellulolytic systems, crystalline celluloses and coarse particles were resistant to attack. Gravimetric assays indicated that lignification reduced digestibility more than could be predicted from the lignin content alone, suggesting that in part the resistance of lignified fibers results from masking of the cellulose. The protective effect of lignification in jute is further supported by the fact that alfalfa stems having the same lignin content as jute were about five times as digestible as jute. Acid treatment enhanced the resistance of both jute and cotton to degradation. Alkali treatment decreased resistance to degradation of both jute and cotton, the effect on jute being particularly pronounced. Pure α-celluloses were rapidly degraded regardless of their origin. Stimulation of cellulose degradation by the hemicellulose present in the holocellulose was negligible.