Deconstruction of lignocellulosic material by bacterial consortium

Abstract

The awareness of environmental threats due to the rising global demands for energy and the reduction of energy resources originating from fossil fuels have led to the search for alternative energy sources, cleaner and renewable. The lignocellulosic biomass is an abundant renewable resource on earth and it can be an excellent substrate for the sustainable production of second-generation alcohols, such as ethanol and butanol. Furthermore, lignocellulose material can be used for the synthesis of important polymers in several industrial segments.On the other hand, the structural complexity of lignocellulose is a major challenge for use of biomass for the production of alcohols or any other compound. Thus, the use of biomass for the production of biofuels from plant residues requires several steps which significantly increase production costs. Currently, one of the most expensive steps during the production of alcohol from biomass is the enzymatic hydrolysis of lignocellulose for the release of sugars capable of being used in the fermentation process. The hydrolysis of this substrate requires the concerted action of various enzymes. The biomass conversion enzymes work together to benefit from synergy between their specificities (for different components of lignocellulose) and attenuation of its inhibition by different degradation products.Many organisms have enzymes that allow the breakage of lignocellulose biomass and the use of its sugars. Many of these enzymes are secreted separately or form complexes in order to act. Considering the aspects related to the difficulties of enzymatic degradation of lignocellulose we have initiated studies using bacterial consortia to carry out these activities. These consortia could promote more effectively the degradation of the biomass by the consorted action of various microorganisms, or provide information and genes that could be used for the synthesis of the set of enzymes involved in the breakdown of cellulose molecules, hemicellulose and lignin degradation.Thus, in a previous project (FAPESP 2010 / 17520-9), two bacterial consortia with important features related to lignocellulose degradation were isolated. These consortia have survived in culture medium containing as a carbon source only residues of lignocellulose (sugarcane bagasse, corn straw or peanut hulls). Furthermore, the consortia in culture medium with these residues release glucose in concentrations from 50 to 200 micromol / ml.Studies of the consortia components showed that there are approximately 50 organisms in supernatant culture medium. It is known in the literature that cellulose degradation may be done by contacting the enzyme on the cell surface with the fibers, so tests should be conducted in order to search which consortium of organisms can be adhered to the material and act on the release of biomass sugars. Similarly, we need to evaluate the interaction among the total microorganisms of the consortium, what is the relation between them that is allowing their survival only in medium with lignocellulose residue, and what is the possibility of using this consortium to facilitate the breakdown and utilization of lignocellulose in biotechnological processes.Considering the characteristics of the isolated bacterial consortia and the preliminary results observed this project is intended to define and exploit bacterial interactions in degrading consortium of lignocellulose with the purpose of using this bacterial population in deconstruction processes of lignocellulolytic material, as well as its isolated or sets specific of enzymes and genes observed. Such approaches are important arising from the need to obtain products with lower price and better suited to the ethanol production technology from biomass, as well as increase the efficiency of the deconstruction process of lignocellulolytic material for its use in other biotechnological processes within the current concept bio-refineries. (AU)