Monday, April 30, 2007

Mild chemical pretreatment of wheat straw to improve its susceptibility to enzymatic saccharification

Nóra Szijártó, Enikő Varga, Attila Deák, Zsófia Kádár, and Kati Réczey. Department of Agricultural Chemical Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, Budapest, 1111, Hungary

Wheat straw is a major agricultural by-product in Central and Eastern Europe. It is mainly used today as animal feed (7%) and bedding (87%), and only partially as an industrial raw material (6%), for example as the substrate of mushroom production. Because the region witnesses a dramatic decrease in animal breeding, crop residues that are mainly used in stock-raising today need to be utilized by other means in the near future.

Residues under discussion are mainly composed of structural polysaccharides like cellulose and hemicellulose, embedded in the complex structure of lignocellulose, conserved by lignin. Cellulose has tremendous alternatives of utilization, especially after its enzymatic degradation to glucose that can easily be fermented to fuel ethanol or other valuable bulk products. In order to make the cellulose content in the lignocellulose matrix accessible to cellulose degrading enzymes, the complex structure of lignocellulose has to be - at least partially - degraded. To achieve this, we employed different chemical treatments, which were thereafter evaluated via enzymatic degradability of the treated material by commercial cellulases. Conversions obtained after the applied chemical treatments were lower than those achieved after the well-known high-temperature and/or high-pressure processes like steam pretreatment or wet-oxidation. However, because of the low capital and operational costs, simple chemical treatments can still be considered as cost effective alternatives of those well-established pretreatment processes. In particular, they can be of interest when only partial degradation of lignocellulose is needed, like in the feed industry, biogas fermentation, or in the production of mushroom substrate.