Biomass: a reservoir for biorefineries

The cell wall plays a key role in the recovery of lignocellulosic biomass. It is a major reservoir of raw materials for the production of biobased materials and molecules of interest (biologically active molecules, platform molecules, synthons, etc.). We are working on both dedicated crops and plant co-products.

Exploiting lignocellulosic biomass in eco-responsible conditions means favouring enzymatic treatments and working with a high solids content to minimise water consumption.

For this reason, we are interested in the behaviour of enzymes in poorly hydrated and highly organised environments. In our recent work, we have studied the impact of these conditions on pectin-degrading enzymes. Indeed, pectins affect the accessibility of other wall components to enzymatic degradation and thus contribute to the recalcitrance of plant biomass. Eliminating them therefore encourages the deconstruction of pectin-rich biomass. We therefore compared the action of different enzymes on citrus peels, varying the amount of water from 95% to 65%. We showed that reducing the water content reduced the efficiency of pectin-degrading enzymes, more significantly for hydrolases than for lyases. In parallel, low-field NMR experiments have shown that solid loading clearly affects water mobility, and that these changes in mobility vary according to the enzyme used.

This new information is useful for the biorefining of pectin-rich plant materials when enzymes are used.

Li F., et al. 2021. Effect of solid loading on the behaviour of pectin-degrading enzymes. Biotechnology for Biofuels, 14, 107. https://doi.org/10.1186/s13068-021-01957-3

Lignocellulosic biomasses such as walnut shells and pea pods are of particular interest as part of the drive to reuse under-utilised agro-industrial waste. They represent 50% and 30 to 65% of the harvested product respectively. We have therefore evaluated them as sources of molecules of interest, in particular for the production of xylooligosaccharides, which are known to have prebiotic activity. Walnut shell and pea pod hemicelluloses consist essentially of a glucuronoxylan with a few arabinose branches. These hemicelluloses were hydrolysed to xylooligosaccharides using an endo-xylanase. Maximum xylan conversion rates of 70% for walnut shells and 90% for pea pods were achieved, demonstrating the value of these two biomasses as sources of oligosaccharides with prebiotic activity.

https://www.inrae.fr/actualites/co-produits-agricoles-sources-molecules-dinteret

Vojvodić Cebin A. et al., 2021. Valorisation of walnut shell and pea pods as novel sources for the production of xylooligosaccharides. Carbohydrate Polymers, 263, 117932. https://doi.org/10.1016/j.carbpol.2021.117932