-According to the United Nations, by 2050 there will be a world population of 9700 million inhabitants.
-The effects of climate change with prolonged drought will drastically affect grain production.
-The depletion of non-renewable fossil energy reserves (oil, gas) will pressure the production of cereal ethanol.
-There will be an unprecedented competition between humans and animals for food resources (Corn, wheat, sorghum, soy, etc.).
-The producers will be forced to increase the use of fibrous by-products and low digestibility in poultry, pig and aquaculture (DDGS, Wheat bran, rice bran, rice husk, soybean, sugar beet shell, bagasse cane, seaweed flour, even post harvest ground residues).
6 Enzymes will be important in the future to improve the digestibility of fibrous ingredients.
- Cellulases- Cellulose
- hemicellusas - hemicellulose
- Pectinases - Pectin
- Ligninases - Lignin
- Xilanasasàs – arabinoxylanes
- Beta - Glucanasases - Beta-Glucans
- α-Amylases – Starch
Cellulose: the most abundant natural polysaccharide in nature
Cellulose is the main component of the cell wall of most plants. A young plant cell contains approximately 40% cellulose and 50% wood. The most representative example is cotton that contains more than 90% cellulose.
Taking into account its chemical structure, it is defined as a linear polysaccharide formed by glucose residues linked by beta 1-4 (β-1,4) bonds. The β configuration allows cellulose to form long, linear chains, which are joined together by means of hydrogen bridge bonds, leading to the formation of microfibrils. These regions, known as crystalline regions, are highly ordered and give the characteristics of insolubility, rigidity and resistance to enzymatic attack.
In certain regions of the microfiber bundle, the chains are broken by their hydrogen bonds and regions called amorphous are formed, which are hydrated allowing certain enzymes to attack and degrade cellulose.
Although it is made up of glucose units, animals cannot use cellulose as an energy source, since they do not have the enzymes necessary to break the β-1,4-glucosidic bonds. However, in the intestine of ruminants, herbivores and termites, there are microorganisms that have an enzyme called cellulase that breaks this bond. When the cellulose molecule is hydrolyzed, glucose molecules are available that can be used as an energy source.
In addition to the ruminant and pseudo-ruminants animals (horses, rabbits, etc.) we must study the digestive process of impressive species such as the xylophages: termites, woodworm, wood moths and the white rot fungus (Botryosphaeria dothidea) that has the capacity of unfolding the lignin (ligninolytic enzymes).
Insoluble fibers (cellulose, hemicellulose and lignin) have little nutritional contribution in monogastric animals, fibrolytic bacteria of the blind and large intestine ferment (cellulase) and produce volatile fatty acids (AGVs), butyric, acetic and propionic that are absorbed in the blood. Lignin is indigestible.
Trichoderma reesei is a fungus widely used for the production of cellulase and xylanase.
-A new procedure allows converting the inedible cellulose into rich starch.
-Glucose is, as we know, the main source of carbohydrate energy.
The amount of glucose that plants generate each year in the form of cellulose is estimated at about one hundred eighty billion tons. Obviously, all that glucose cannot be used for food, but could we do something to transform cellulose into starch? Achieving this transformation would mean taking an important step to, if not eliminate, at least reduce hunger in the world and, at the same time, generate raw material for the manufacture of biofuel.
A group of Chinese and American researchers address this issue and have designed a way to transform cellulose into starch that, for the moment, is not too effective, but that can improve a lot in the future. The basic idea consists of the following: Using molecular biology techniques, the researchers introduce a series of genes into the Escherichia coli bacteria, old known from laboratories around the world. One of these genes produces an enzyme capable of breaking down cellulose and breaking it into fragments of two glucose molecules, fragments that, however, remain indigestible.
Another of the genes produces an enzyme that is now able to separate those two glucose molecules into individual molecules. Finally, those individual glucose molecules can be used by a third enzyme, which now binds them together in a suitable way to form starch. Extracts of these bacteria are capable of transforming cellulose into starch.
Although the procedure works, at the moment it is very expensive. It would cost a million dollars to convert 200 kilos of cellulose into 20 kilos of starch, which would only cover the energy needs of a person for 80 days.