Degradation of Cellulose and Hemicellulose by Ruminal Microorganisms

Abstract

As major structural components of plant cell walls, cellulose and hemicellulose are degraded and fermented by anaerobic microbes in the rumen to produce volatile fatty acids, the main nutrient source for the host. Cellulose degradation is carried out primarily by specialist bacteria, with additional contributions from protists and fungi, via a variety of mechanisms. Hemicelluloses are hydrolyzed by cellulolytic bacteria and by generalist, non-cellulolytic microbes, largely via extracellular enzymes. Cellulose hydrolysis follows first-order kinetics and its rate is limited by available substrate surface area. Nevertheless, its rate is at least an order of magnitude more rapid than in anaerobic digesters, due to near-obligatory adherence of microbial cells to the cellulose surface, and a lack of downstream inhibitory effects; in the host animal, fiber degradation rate is also enhanced by the unique process of rumination. Cellulolytic and hemicellulolytic microbes exhibit intense competition and amensalism, but they also display mutualistic interactions with microbes at other trophic levels. Collectively, the fiber-degrading community of the rumen displays functional redundancy, partial niche overlap, and convergence of catabolic pathways that all contribute to stability of the ruminal fermentation. The superior hydrolytic and fermentative capabilities of ruminal fiber degraders make them promising candidates for several fermentation technologies.

Comparative nutritional evaluation of the leaves of selected plants from the Poaceae family (bamboos and grasses) for sustainable livestock production in Ghana

“…In the current study, both bamboo leaves and the grasses were fibrous, thus, can enhance chewing and stimulate saliva to maintain the rumen pH required to prevent metabolic disorders in ruminants fed high-grain diets. Ruminal pH considerably affects cellulose degradation (Weimer, 2022). Our data showed that compared to the grasses, the bamboo leaves had relatively lower concentrations of cellulose (a less readily digestible plant cell wall component) and a higher level of hemicellulose (a more easily digestible fiber fraction).…”

Effect of banana peduncle fiber on the mechanical, water, and degradation properties of hybrid composites made from modified soy resin

“…Due to the resole, the BR composite (79.5°) has a greater contact angle value than the BS2 (68.6°) and BRS (73.8°) composites, indicating that it is more hydrophobic. The contact angle of BS composites non‐linearly improved with increase in fiber content, that is, 67.4°–68.6°, and then decreased to 67.2°, while water absorption values decreased from 37.8% (BS1) to 35.3% (BS2) and then increased to 37.8% (BS4), respectively 36 . Thickness swelling value of BS composite decreased from 40% (BS1) to 38.6% (BS2) and increased to 40.8% (BS4).…”

“…The contact angle of BS composites non-linearly improved with increase in fiber content, that is, 67.4 -68.6 , and then decreased to 67.2 , while water absorption values decreased from 37.8% (BS1) to 35.3% (BS2) and then increased to 37.8% (BS4), respectively. 36 Thickness swelling value of BS composite decreased from 40% (BS1) to 38.6% (BS2) and increased to 40.8% (BS4).…”

Deciphering the Impact of Nutrient Composition and Tissue Structure on Rumen Microbiome Dynamics in Roughage Degradation

“…In our study, pathways related to amino acid, lipid, nucleotide, carbohydrate, inorganic ion, and coenzyme transport and metabolism, as well as translation and ribosomal structure biogenesis, exhibited an initial decline followed by an increase between 4 to 72 hours. This trend suggests microbial competition for nutrients during the early fermentation stage [68], succeeded by enhanced growth due to nutrient release from cellulose degradation in later fermentation phases [69]. The KEGG pathways analysis revealed that carbohydrate metabolism [70], amino acid metabolism [71], and energy metabolism pathways [71] had elevated relative abundances, underscoring their significance in the degradation of various roughage types [72].…”