Tuesday, May 1, 2007 - 7:00 PM

Cell wall limitations to efficient lignocellulosics bioconversion

Brigitte Chabbert, Imen Boukari, Johnny Beaugrand, Caroline Remond, and Philippe Debeire. UMR FARE, INRA, 2 Esp. R. Garros, BP 226, Reims, 51686, France

Besides their main application as feed for livestock, lignocellulosics could be of industrial interest for non-food products (bulk chemicals, bioenergy, etc.), notably through enzymatic bioconversion and upgrading. Improvement and development of efficient enzymatic tools for biomass conversion require in depth knowledge of the main limitations brought by lignified cell-walls. Apart from adequation of the plant substrate to the catalytic efficiency of hydrolytic enzymes, several factors would impact the way the enzyme can act on lignocellulosics. Notably, the impact of chemical and physical barriers displayed by lignified cell wall would affect enzymatic activities. Indeed, the cell wall network, which is maintained by a variety of covalent and non-covalent interactions, may impede the enzyme penetration and progression and/or limit substrate accessibility.
Non-invasive methods such (immuno)cytochemistry provide specific information on the cell wall heterogeneity at both cellular and subcellular levels. Notably, complexity of the cell wall networks can be clearly evidenced following enzymatic destructuration. Moreover, enzyme engineering aimed at modulating enzyme size and activity can provide a variety of molecular tools that will allow significant knowledge of the organizational heterogeneity of plant cell walls. Strategy based on in muro probing of the wall network in plant tissues would take advantage from comparative studies on various botanical plant materials. Furthermore, the use of in vitro systems of the lignin-polysaccharide matrix would provide information on the way supramolecular organisation of the wall polymers may affect the enzymatic breakdown of lignocellulosics.