MANNABREAK - In search for new enzymes: toward the preparation of galactoglucomannan elementary bricks extracted from wood

Galactoglucomannans are the main hemicelluloses contained in softwood species (Spruce, Pine, …). In the process currently used in the paper industry to extract cellulose (kraft process), part of these hemicelluloses are degraded and end up in the liquor with the lignin. This liquor is concentrated and burnt to supply the necessary energy for the process, and in most mills, extra energy is sold to the electrical network. But the calorific value of hemicelluloses being much lower than that of lignin, burning them could be considered as a rather low value valorization, and other valorization ways are currently explored. This project proposes to investigate the biotechnological production of new series of oligosaccharides with high economic value from these hemicelluloses.

Hemicelluloses can be extracted directly from wood during an autohydrolysis process which integration in lignocellulosic biorefineries is currently under development. The main drawback of this process lies in the solubilisation of small hemicellulose polymers (degree of polymerization up to 25-30), still bearing some acetyl groups or methylglucuronic groups, which are lost in the process. The work proposed in this project deals with the search for new degrading and modifying enzymes able to specifically extract galactoglucomannans without degrading them, and tune their structure (in terms of degree of polymerization, of saccharide composition and of substituents amount). Such compounds can be valorized as ingredients in nutraceutical or cosmetic applications. At the end of the project, the set of enzymes produced will be used to prepare series of oligo-saccharides with controlled structures.