Cellulose in Digestion

Introduction of Cellulose Digestion

Cellulose makes up about 30% of the wall of the plant cell and it serves as the connection between the cells and the tissues. The main substance found as a structural component in the cell wall of the plant is cellulose by which plants remain stiff and upright.  As a fiber, it has great importance in the diet. But it cannot be digested by humans because the digestive system of humans is assisted by it. It helps the food to push the waste out of the body. In animals, microbes secrete cellulose to digest it. The digestion of cellulose occurs in a four-chambered stomach. Cellulose is the most abundant organic polymer founded on the earth which occurs naturally.


Introduction to what is Cellulose 

Cellulose is a complex polymeric carbohydrate molecule that comprises thousands of glycosidic linkages in the form of a linear chain. The chain is unbranched and straight consisting of linked D-Glucopyranose bonded by hydrogen bonds producing a substance which in its pure form is insoluble and inert.

Structure of Cellulose    

A large number of organisms ranging from the bacterium Acetobacter xylinum synthesizes cellulose from the forest trees. A good amount of cellulose is produced by A. Xylinum and also this bacteria is used in the study of cellulose biosynthesis. The protein named enzyme cellulose synthase present in the membrane synthesizes cellulose as well as catalyzes the glucose polymerization from UDP- glucose into the product of cellulose.

There are many bacteria, Dictyostelium disodium, and higher plants from which genes for cellulose synthesis can be identified.  From the Cellulose which is present in plants to the bacterial cellulose, all are arranged in a similar way from the microfibrils as chains of polysaccharide and from ribbon bundles of microfibrils.

Reasons Why Humans Cannot Digest Cellulose

In the human body, cellulose cannot be digested due to a lack of appropriate enzymes to break the beta acetal linkages. The human body does not have the digestive mechanism to break the monosaccharide bonds of cellulose.  Although cellulose is indigestible then also it helps in the smooth working of the intestinal tract.

But, it plays a vital and necessary role in the human body because it is an excellent source of fiber. Every kind of sugar can be digested by the enzymes secreted from the human mouth, liver, and stomach except cellulose. There are some foods like fermented food, grains, and vegetables which are hard to digest or are indigestible.

Cellulose Digestion in Herbivores

By means of the symbiotic gut bacteria, cellulose can be digested by herbivores with the help of monogastric digestion. Herbivores are less efficient than ruminants in the case of extracting energy from the digestion of cellulose. Here, cellulose is digested by microbial fermentation.

Herbivores eat plant materials as their food and the cell walls in plants contain cellulose. By these, the cellulose breaks into absorbable substances. Then it gets absorbed into the body and provides nutrition.

Cellulose Digestion In Termites

Termites are also unable to digest the cellulose then also they feed cellulose present within the wood. Some microorganisms live in the gut of termites. These microorganisms are named as mastigophorans.  Termites break down the wood and microorganisms produce the by-product which can be digested by both the organisms and termites.

Termites rely on their own celluloses. It is believed because they have the strong activity of cellulose in the midgut. Acetic acid and other acids are released at the time of the digestion of wood cellulose.

Cellulose Digestion in Ruminants

In ruminates, the place of digestion of cellulose is the four-chambered stomach and it is digested with the help of bacteria and enzymes present there. The first compartment is the rumen where the plant material is stored temporarily and later it gets processed and also gets exposed to bacteria in the initial stage. Anaerobic bacterial digestion occurs as bacteria can break down the cellulose. The presence of several compartments in the stomach helps in the process. After the partial digestion in the stomach, they chew their cud. This process helps in further breaking of the material.

The monosaccharide glucose is produced by the breakdown of the plant fiber by Ruminococcus bacteria. A further breakdown can occur with the help of glucose. In ruminant, the symbiotic relationship can be seen in which the digestion of fiber is enabled without encoding for more enzymes in their own genomes for this process.

FAQ (Frequently Asked Questions)

1. What is the importance of cellulose in our diet?

The importance of cellulose in the human diet is that it provides the essential fiber which helps in the digestive system. This type of fiber is called insoluble fiber. Humans are benefited from it as it helps in moving the food fast through the digestive system. The tendency of constipation is reduced and prevented by it. The people who do not eat fiber can suffer from diverticulitis which is caused due to infected and inflamed diverticular.

Two types of fiber are recommended, these are soluble fiber and insoluble fiber. Having a variety of fruits, vegetables, and seeds which contain cellulose is healthy for human beings.


2. What is produced at the end of cellulose digestion?

The process of cellulose digestion occurs in the body of animals. At the end of this process, it produces carbon dioxide, energy, and water. With the help of an enzyme, it travels through a long trip. There, it is converted to sugar which burns and results in the production of energy. Carbon dioxide and water are its by-products. 

The process of synthesis of celluloses and digestion of cellulose both occurs with the help of several species of bacteria. Most importantly, the major end products of cellulose’s microbial digestion are lactic acid, hydrogen, methane, and CO2.