New thermostable enzymes for bio-ethanol production from lignocellulosic materials.

In recent years, growing interest has been devoted to the conversion of biomass into fuel ethanol since the employment of agro-industrial residues in bioprocesses could provide alternative substrates and also could solve their disposal problem. Agronomic residues such as corn stover, wheat or rice straw, forestry and municipal solid wastes represent a large potential renewable reservoir of sugars that could be converted into useful fuels. Many pre-treatment techniques comprising mechanical size reduction, chemicals addition or steam exposure have been developed that allow a significant increase of yields in the subsequent enzymatic hydrolysis step. However, the harsh conditions required by these techniques can cause problems when using conventional enzymes in the saccharification step. In fact, one of major drawbacks is represented by the lack of thermostability of most cellulases and hemicellulases. As consequence, thermophilic bacteria have received considerable attention as sources of highly thermostable cellulolytic and xylanolytic enzymes since their unusual properties may result in the development of novel biotechnological processes. Here, we report on the screening and isolation of themostable cellulolytic and hemicellulolytic activities from (hyper)thermophilic bacteria and archaebacteria as potential biocatalysts for bio-ethanol production from agricultural pretreated wastes. Preliminary results on saccharification of pretrated biomasses are also reported.