Giant reed (Arundo donax L.) as cellulosic energy crop for second generation bioethanol.

The search for alternative energy sources for the development of sustainable fuels is an environmental and economic priority. During the last decades, considerable attention has been addressed to the bioethanol of "second generation" that derives from the cellulosic biomasses. Recent technological developments have identified many plants as possible sources of bioethanol, and in the European Union, giant reed (Arundo donax L.) is considered one of the possible cellulosic energy crops. This perennial species has high biomass productivity, it is very hardy and needs virtually no fertilizers nor herbicides during growth. Consequently, this grass, containing about 40% cellulose, is regarded as an attractive potential feedstock for bioethanol production. In this report we show data about the enzymatic saccharification of Arundo donax by cocktails of commercial enzymes but, in order to allow enzymes to attack cellulose and increase their efficiency, it was necessary to pretreat the biomass to enhance its susceptibility to the enzymatic action. A. donax was submitted to the steam explosion treatment (210 °C, 10 min), and the exploded substrate was recovered (91% yield) and washed with hot water (65 °C) to separate the hemicellulose stream from the insoluble residue (cellulose 51% + lignin). The pretreated material was hydrolyzed with mixtures of enzymes at different incubation times, pH and temperatures. The highest conversion yield in glucose, obtained at 50°C and pH 5.0 with a combination of cellulase and beta-glucosidase, was 95%. Other pretreatments (acid and alkaline), and different concentrations of substrate and/or enzymes were investigated and reported