The Chemical Entities of Biological Interest (ChEBI) ontology is downloaded weekly from EMBL-EBI at http://www.ebi.ac.uk/chebi/. The data is made available under the Creative Commons License (CC BY 3.0, http://creativecommons.org/licenses/by/3.0/). For more information see: Degtyarenko et al. (2008) ChEBI: a database and ontology for chemical entities of biological interest. Nucleic Acids Res. 36, D344–D350.
A complex biopolymer that is a component of plant cell walls which is used as a renewable feedstock for the production of paper, fuels, and chemicals (also used as a feed supplement in the poultry industry). Its structure comprises of three main types of carbon-based polymer -- cellulose, hemicellulose and lignin. Generally, its biomass consists of 35-50% cellulose, 20-35% hemicellulose, and 10-25% lignin with proteins, oils, and ash making up the remaining fraction.