Effect of Particle Size on the Digestion Rate of Purified Cellulose by Rumen Cellulolytic Bacteria in Vitro

Purified cellulose (approximately 100-mesh) and samples wet-ball-milled 6, 24, and 96 hr. were used as substrates for in vitro fermentations with rmnen cellulolytic bacteria. Rates of digestion were compared by taking samples at 6, 12, 22, 30, and 48 hr. The data suggested that when maximum cellulose digestion is occurring, and the substrate is nonlimiting, cellulose digestion of the different samples is oecmwing at a similar rate. The apparently faster digestion rate of the ball-milled cellulose appears to be caused by a reduction of the lag phase. Possible explanations for this are discussed. An in vitro method using calibrated large flasks, which can be sampled at various time intervals, is also described.