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Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In human nutrition, cellulose is a non-digestible constituent of insoluble dietary fiber, acting as a hydrophilic bulking agent for feces and potentially aiding in defecation.
Cellulose breakdown is of considerable economic importance, because it makes a major constituent of plants available for consumption and use in chemical reactions. The specific reaction involved is the hydrolysis of the 1,4-β-D-glycosidic linkages in cellulose, hemicellulose, lichenin, and cereal β-D-glucans. Because cellulose molecules bind ...
Monogastrics cannot digest the fiber molecule cellulose as efficiently as ruminants, though the ability to digest cellulose varies amongst species. [2] A monogastric digestive system works as soon as the food enters the mouth. Saliva moistens the food and begins the digestive process.
While foregut fermentation is generally considered more efficient, and monogastric animals cannot digest cellulose as efficiently as ruminants, [5] hindgut fermentation allows animals to consume small amounts of low-quality forage all day long and thus survive in conditions where ruminants might not be able to obtain nutrition adequate for their needs.
Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals, such as termites can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water.
The hydrolysis of cellulose results in sugars, which are further fermented to acetate, lactate, propionate, butyrate, carbon dioxide, and methane. As bacteria conduct fermentation in the rumen, they consume about 10% of the carbon, 60% of the phosphorus, and 80% of the nitrogen that the ruminant ingests. [ 31 ]
Most animals, however, do not produce cellulase; the enzyme needed to digest cellulose. However, some animals and species have developed symbiotic relationships with cellulase-producing bacteria (see termites and metamonads.) This allows termites to use the energy-dense cellulose carbohydrate. [1]
Bacteroides thetaiotaomicron is a common bacterium in the human gut microbiome that has evolved alongside humans to support digestion and general health. Over time, this bacterium developed the ability to break down complex carbohydrates into simple sugars, which helps the host species get more energy from the food it eats.