Aerobic and anaerobic plant cell wall decomposition by microorganisms is a crucial process in carbon cycling on Earth. Our group focuses on key actors of this step, the anaerobic bacteria performing an efficient degradation of the plant cell wall polysaccharides, especially the model bacterium Ruminiclostridium cellulolyticum :
These bacteria produce large extracellular multienzyme complexes termed cellulosomes (figure 2) containing an array of cellulose-degrading enzymes (cellulases) and hemicellulases targeting the heterogeneous polysaccharides surrounding the cellulose fibers.
The extracellular degradation of the various plant polysaccharides performed by the cellulosomes and accessory enzymes (figure 3) is under investigation.
We also investigate other cellular processes such as the signalization/regulation of genes important for polysaccharide degradation, the transport across the membrane of the released oligosaccharides, and their final depolymerisation into assimilable sugars. For this purpose, we combine biochemical (artificial minicellulosomes, enzyme purification and characterization), genetic (gene inactivation/overexpression, regulation) and biophysical (ITC, microscopy) approaches. Examples of polysaccharide catabolisms currently explored by our group are reported in figures 4 and 5.
Our group also focuses on recently isolated (anaerobic) microorganisms which deconstruct crystalline cellulose even faster. Investigation of their potent cellulolytic systems through genetic and proteomic approaches may lead to the discovery of novel types of cellulases and hemicellulases.
The technology of the artificial minicellulosomes that we have pioneered, is also exploited to engender a cellulolytic phenotype in bacteria of industrial interest producing primary alcohols. Currently, our purpose is to create an engineered microorganism capable to directly convert cellulose into biofuel such as butanol at low cost in a consolidated bioprocessing.