Innovative pretreatment to increase cellulose accessibility of rape straw within three days: a new lead for valorization of agriculture residues

Agriculture residues are abundant and energy-rich lignocellulosic biomass. Their high cellulose content makes them good material for the production of both liquid and gaseous biofuels. Yet, their application remains limited due to compact chemical structure and the presence of lignin within these biomasses. Aim of this study was to develop a biological pretreatment method which is quick and cost-effective for agriculture residues valorization, particularly through anaerobic digestion. A typical and recalcitrant residue, rape straw was chosen as the model substrate for the study. In this work, we present: i) a pretreatment method of rape straw by using an innovative pretreatment and ii) an experimental protocol for determination of cellulose accessibility of agriculture residues. The experiments were carried out in reactors. Cellulose accessibility to cellulase (CAC) of the substrate, rape straw, was determined at several moments of incubation by a recombinant protein a cellulose-binding module (CBM) (Hong et al., 2007). Describing the total surface of accessible cellulose, this parameter represents the amount of cellulose available for cellulase. Results showed that the innovative pretreatment is necessary for the release of accessible cellulose from the substrate, allowing the CAC to increase about one fold after 3 days of incubation. The innovative pretreatment showed a better performance, by increasing the CAC for five to eight folds in 3 days. Studies of microbial community suggests that microorganisms, especially bacteria which were initially present on the straw might be responsible for the degradation, while introducing new strains may have no significant effect.