Xylanase is a class of enzymes produced by microorganisms to break down a component of plant cell walls known as hemicellulose. Xylan is a polymer of glucose molecules and a major component of hemicellulose, helping to hold the cell walls together. Thus, the action of a xylanase enzyme helps to break down plant cell walls. This activity has applications in the food and paper-making industries, along with uses in agriculture and for human health.
There are a number of different types of xylanases produced by different microorganisms. These enzymes act under different conditions, such as at different pH levels and temperatures. There is a lot of biochemical engineering work done with xylanases, to determine the optimal enzyme for a particular application. Frequently, genetically modified fungi are the source of xylanase used in commercial applications.
Xylan is a gummy, mucous-like substance that is sometimes called wood gum. It can cause fruit juices to be cloudy. Xylanase is sometimes used in conjunction with other cell-wall degrading enzymes, such as pectinase and cellulase, to clarify the juice, so it becomes clear.
Wheat has a lot of xylan, which affects the consistency of wheat dough. One of the main applications of xylanase is to improve the quality of dough. For instance, water absorption, stability, and workability can be improved with the use of this enzyme. Also, fermentation for alcohol production utilizes xylanase to release the gummy material, so it can be fermented.
This type of enzyme is also used to improve grains and other plant-based materials used as animal feed. In combination with other cell wall degrading enzymes, it helps break down the cell walls. This makes it easier for the animals to digest. An example of the benefits include increased milk production by dairy cows.
The same principle is used with xylanase in preparations designed to help the human digestive system. Combinations of various enzymes that break down plant materials are sold to be taken as supplements. Specific microbial enzymes that act over a broad pH range are chosen, in hopes that they will retain activity in the harsh environment of the stomach. It is not clear whether these enzymes survive digestion by the stomach’s natural enzymes.
Xylan is of interest as a renewable resource, since it is a large component of agricultural waste, such as straw, that could be used as a source of biomass. For such a process to be successful, the plant cell wall must be broken down into smaller, usable fractions. Various xylanases are being investigated for use in helping to degrade the cell walls on an industrial scale.
Another use for xylanase is in the paper-making industry. It is used as an alternative to chlorine in bleaching wood pulp. This stage comes before the paper is manufactured, and cuts down on the amount of chemicals used in the process.