Innovative enzymes for bioethanol production from lignocellulosic materials

The general aim of this work was to add new knowledge on novel hemicellulolytic enzymes involved in the hydrolysis of lignocellulosic materials, considered as a key process for the bioethanol production. Therefore, it is not only focused on (hemi)cellulolytic enzymes from mesophilic fungi and bacteria but also on newly isolated and characterized xylanase and ?-xylosidase from the thermophilic bacteria Geobacillus thermodenitrificans A333 and Anoxybacillus sp. 3M, respectively. The covered fields involved the production and purification of the novel thermo-alkali tolerant hemicellulases and the characterization of these enzymes by their activity, substrate specificity and hydrolytic potential. The present work was also focused on the definition of enzymatic cocktails through the identification of the enzyme components of bacterial and fungal origin most useful for improving the complete hydrolysis of lignocelluloses and the exploration of the possible synergies among them. In order to convert lignocellulosic materials from agro-residues into reducing sugars, pretreatments and enzymatic hydrolysis of the biomasses has been performed. Different enzyme cocktails composition were defined by using various commercial and in house developed cellulases, xylanases, ?-xylosidases and arabinosidases, to obtain the efficient hydrolysis of Arundo donax, corn cobs and BSG. Since each biomass responds differently to pretreatment methods, an appropriate chemical pretreatment method was used for BSG and two different pretreatments involving chemical and physical methods were tested for their efficiency on A. donax. Though research about the conversion of biomass to ethanol is vast and this productive process is since long time known, its commercialization is restricted by the elevated costs and the limited efficiency. This research intends to demonstrate that using agro-residues as substrates, high yields of reducing sugars are possible, using the appropriate pretreatments and enzyme cocktails. The removal of the limitation imposed by poor yields after the enzymatic hydrolysis, would result in an increased efficiency for ethanol production, which is a key stepping stone to its commercialization. Also, increasing the recovery of the co-product of (hemi)celluloses hydrolysis, as xylose and arabinose, would also allow an effective utilization of this resource.