Sugars in hemicellulose

Wood is made of cellulose, hemicellulose and lignin which is why it is called lignocellulose.

Cellulose is a crystal of glucose molecules with the formula (C6H10O5)n. It is a polysaccharide consisting of a linear chain of several hundred to over ten thousand linked glucose molecules.

Hemicellulose is not crystaline,  it has a random, amorphous structure with little strength.  It can be made of polymers of glucose, xylose, mannose, galactose, rhamnose, and arabinose.  The polysaccharides of these sugars are:   xylan, glucuronoxylan, arabinoxylan, glucomannan, and xyloglucan. They help lignin bind the cellulose together.

Lignin is the second most abundant non fossil organic compound on Earth after cellulose.

 It is particularly abundant in compression wood but scarce in tension wood.

Cellulose content
  %
Wood 40-50
Grass  
Hemp 75
Cotton 80

Hemicellulose is made of:

     Pentoses - xylose, arabinose

     Hexoses - mannose, glucose, galactose

     Sugar acids - glucuronic acid,

Hardwood hemicellulose is mainly xylan, a polysaccharide of xylan, of pentose.

Softwood is mainly glucoannan, a polymer of hexoses.

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Boosting galactan sugar in plants

Galactan is a hexose easily fermented to ethanol or butanol. New research has found that it can be increased in plants.

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Increasing galactan in willows

What researchers had previously observed, was that willow trees cultivated in naturally windswept areas were producing more biofuel than willow in relatively non-windy areas.

The team cultivated willows at a 45 degree angle under controlled conditions, and compared their genetic traits with trees growing naturally at severe angles in an extremely windy site in Scotland.

The key finding was that growing at an angle, under duress, activates a genetic trait that tries to counteract whatever force is pushing the tree sideways.

The end result is that the sugar molecules in the stems of the willow are strengthened into higher-energy sugars, which can be processed into biofuel through fermentation more efficiently than sugars from unstressed trees. The yield is about five times greater for stressed willow than for their non-stressed counterparts.

Ref Clean technica