Scientists from the University of Copenhagen (Denmark) and the Southern Research Station of the United States Department of Agriculture (USDA) have reported the effect of hydrothermal pretreatment of wheat straw on the straw’s cell-wall matrix and its composition, using atomic force microscopy and scanning electron microscopy. Pretreatment is usually the first step in the production of cellulose-ethanol from lignocellulosic biomass, such as wheat straw. The purpose is usually to delignify (remove lignin) and to render the cellulose fibers in the plant biomass more susceptible to enzymatic conversion into sugars for ethanol production. Hydrothermal treatment is one pretreatment option. Under this method, the chopped and preheated (80 ^oC) wheat straw is placed inside an airtight reactor and injected with stream at 195 ^oC for an average reaction time of 6 minutes. In contrast to steam explosion treatment (heating the biomass with steam under pressure, then rapidly releasing the pressure, causing the fibers to explode), hydrothermal treatment is reportedly a milder pretreatment method. According to the report, “recent results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system”. The scientists found that hydrothermal treatment “does not degrade the fibrillar structure of cellulose but causes profound lignin re-localisation”. Partial removal of wax and hemicellulose was also observed. The changes in hydrothermally-treated wheat straw was similar to those in (the more intensive) steam-exploded wheat straw. Details of the report can be found in the online access, peer-reviewed journal, Biotechnology for Biofuels (URL above)..