Enhanced digestion of bio-pretreated sawdust using a novel bacterial consortium: Microbial community structure and methane-producing pathways

Anaerobic digestion is widely considered the most cost effective and sustainable technology for bio-waste to energy valorization. Several substrates show a certain recalcitrance to the process evolution, such as sawdust. To this aim, in this study, sawdust has been subjected to a biological pretreatment by means of a novel bacterial consortium before its biomethanation. This novel lignocellulose-degrading bacterial consortium, isolated from several carpentries, has been constructed to predict the sawdust biological pretreatment efficacy. A five days bacterial pretreatment led to a significant reduction in the sawdust cellulose, hemicelluloses and lignin contents, towards the control, of 35.8, 37.1 and 46.2% respectively. Microbial diversity was analyzed by VIT (R) gene probe. Methanogenesis was carried out through acetoclastic and hydrogenotrophic pathways. For a forty days digestion time, the biological pretreatment enhanced the cumulative biogas and biomethane production respectively of 86.4 and 92.2% compared to the control. With respect to the state of art, the use of this constructed novel consortium pretreatment can significantly increase the biomethane yield, making the digestion more effective and consequently improving the processes economic feasibility. Moreover, this process can be easily integrated in existing biogas plants for making co-digestion processes still more elastic with regard to the available feedstock.