from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of several polysaccharides that are more complex than a sugar and less complex than cellulose, found in plant cell walls and produced commercially from corn grain hulls.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. a mixture of several plant polysaccharides, of smaller molecular weight than cellulose, that are soluble in dilute alkali; they are involved in the manufacture of paper, and are used in the production of furfural and ethanol
from The Century Dictionary and Cyclopedia
- n. A form of cellulose which is easily hydrolyzed by dilute acids and readily attacked by certain enzyms.
Sorry, no etymologies found.
This is obviously due to the conservation of 'hemicellulose' products, which are hydrolysed and dissolved in the treatments for 'crude fibre' estimation.
The researchers modified the E. coli genome, inserting genetic code for the production of an enzyme called hemicellulase, which can break down hemicellulose into smaller sugar molecules which E. coli can then turn into fatty acids.
The leaves and stems, with their tough cell walls made of cellulose, hemicellulose and lignin, are more of a nuisance than anything else.
Plants are made mostly of tough stuff called cellulose and hemicellulose.
Wood has evolved to keep its sugars to itself, covering them with lignin — a substance that gives cell walls rigidity — and then locking them in a matrix of cellulose and hemicellulose protected by complex chemical bonds.
The energy is bound up in the cellulose (especially the hemicellulose), which has to be freed from the inert lignin and then converted into sugars (a process called, naturally enough, saccharification), which can then be fermented into ethanol.
This reduces the sizes of solid particles, changes the consistency from a damp fiber to sludge, and most importantly breaks down the walls of the plant cells, allowing hemicellulose to escape into the syrupy mixture.
Step 2: Enzymes A mix of cellulase enzymes is then added to convert the cellulose and hemicellulose molecules into the simple sugars glucose and xylose.
The latest cellulose ethanol processes use recently identified enzymes to break down the biomass to separate the cellulose, hemicellulose and lignin cheaply, and new genetically modified yeasts which can ferment the C5 xylose sugar from hemicellulose as well as, and at the same time as, the normal C6 fermentation from cellulose.
As for the comments on further breakthroughs required for cellulose ethanol to be practical, I suggest those have recently been made as reported above in 23, including the new cellulase enzymes which liberate both cellulose and hemicellulose.