Carbohydrates from renewable materials: degradation of lignocellulose by conventional or innovative carbohydrate-active enzymes.

Sustainable economic systems can only be based on the wise use of renewable resources and, among potential alternatives, lignocellulosic biomasses represent the most important sources of chemicals and biofuels. In addition, these materials are rich in polysaccharides that can be transformed in high value-added products by suitable processes. The partial or total degradation of the polysaccharide fractions for producing oligo and/or monosaccharides, is an ambitious target that can be efficiently reached with an eco-friendly enzyme-based process. We have selected several lignocellulosic wastes with the aim to produce carbohydrates through an appropriate enzymatic transformation process. Chestnut shells and brewer's spent grains are rich in cellulose, 28 and 35%, respectively while grape shoots also contain up to 15% of their dry weight of non-structural carbohydrates in addition to cellulose. Among these selected biomasses, brewer's spent grains which have also a high content of xylan (27%) have been considered as potential source of xylo-oligosaccharides with recognized prebiotic properties. Moreover recent technological and agronomical studies have identified several plants as possible sources of carbohydrates. In particular, the giant reed (Arundo donax L.) has demonstrated to be one of the more interesting for high mass productivity and cellulose content (40%). It must be underlined that, in lignocellulose, the carbohydrates are embedded in a lignin matrix which hinders the enzymatic action. As consequence, to achieve an effective hydrolysis, pretreatments aiming to destroy the complex structure are required. In this study, we present some results obtained processing the pretreated materials mentioned above. Different treatments and suitable enzymatic cocktails have been tested in order to achieve the highest hydrolysis yield. Soaking of grape shoots by ammonium hydroxide (10%) for 22 h at 70°C, followed by saccharification with amylases and cellulases (50°C, pH 5.0, 72 h) gave the almost complete release of glucose from starch and the 73% from cellulose. Carbohydrates production has been investigated by utilizing both conventional and innovative thermostable enzymes. A novel xylanase from the eubacterium G. thermodenitrificans has been individuated in the culture supernatant after growth on xylan medium. Hydrolysis tests of pretreated lignocellulosic biomasses with the isolated innovative enzymes are in progress for xylo-oligosaccharides production