Scientific activity :

Dr. William Helbert is Research Director at the Centre de Recherches sur les Macromolécules Végétales (CERMAV).

He obtained his doctoral thesis dealing on starch structure in 1994 in CERMAV. He spend two years in Kyoto (Japan) for his post-doc which deal on the structural diversity of cellulose. He joined CNRS in 2001 and obtained the ATIP grant (CNRS) aiming at implementing the "Structure of marine polysaccharides" team in the "Marine plant of biomolecules" laboratory located in Roscoff (France). For about 12 years in Roscoff, he explored the structural diversity of marine polysaccharides using enzymes in frame of national and international collaborative projects involving academic and industrial partners. In 2012, he joined CERMAV which offers precious scientific and technological environment for the development of his research.

His research is articulated around two main axis: 1) The screening of new enzyme activities, and 2) the biochemical characterization of new polysaccharides degrading enzymes and, more especially, enzymes active on marine polysaccharides. These enzymes are used for structural analysis of complex marine polysaccharides and allow preparing of oligosaccharides with original structure and properties.

Axe 1: CRAZY-Polysaccharides: toward the discovery of new polysaccharides degrading enzymes

Polysaccharides collection: we are maintaining a collection of about 200 oligo- and polysaccharides substrates. The collection encompass polysaccharides from animals (glycoaminoglycans, glycogen, chitin), land plant (celluloses, hemicelluloses, pectins, starch), marine algae (agars, carrageenans, alginates, fucans, ulvans,...), bacterial and microalgae polysaccharides. New polysaccharides extracted from microalgae or secreted by marine bacteria are subjected to detailed structural analysis

Screening method: The screening method implemented in CERMAV allows screening complex bacterial extracts and recombinant proteins. The method is based on a colorimetric assays coupled with chromatography and mass spectrometry analyses.

New enzymes: The screening allow phenotyping bacterial extracts by detecting the occurrence of oligo- and polysaccharides degrading enzyme. The method allow comparing the production of enzymes by a strain with the predicted activity from its genome analysis. The difference then observed highlight new enzyme activities or enzymes having new mode of action. Ascribing function to putative or highly divergent polysaccharides degrading enzymes can also be achieved with this method.

Axe 2: Focus on marine polysaccharides degrading enzymes and carbohydrate sulfatase

Carrageenases, agarases and porphyranases are glycosyl hydrolases actives on carrageenan, agarose and porphyran, respectively, which are the main cell wall polysaccharides of red algal. These enzymes are used to decipher the hybrid structure of the red algal polysaccharides aiming at better understand the relationships between their structure with their rheological properties.

In contrast with red and brown algal polysaccharides, polysaccharides extracted from green algae have not been deeply investigated. We have identified the first enzymes involved in the degradation of ulvan degrading enzymes: ulvan lyases and b-glucuronyl hydrolase, which open new perspective in the valorization of green algae.

Marine polysaccharide are often decorated by sulfate ester groups. Therefore, aiming at controlling the structures or reaching complete saccharification of these polysaccharides, marine polysaccharide sulfatases are investigated such as the first endo-carrageenan sulfatases which allows converting, for example, iota-carrageenan in alpha carrageenan.

Liste des publications