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Maize stems are among the most abundant crop residues produced every year. They are rich in cellulose, which makes them attractive for biorefineries. However, like other lignocellulosic biomass, the value of maize stems is limited by their intrinsic recalcitrance, which prevents efficient enzymatic degradation of cell wall polymers. Recalcitrance results from the combination of many multi-scale factors conferred by the close association of the cell wall constituents (cellulose, hemicelluloses and lignin). In order to reduce lignocellulose recalcitrance, pretreatments, such as hot water pretreatment, are carried out upstream of enzymatic hydrolysis

In most studies, the effect of enzymatic pretreatment/hydrolysis on the properties of lignocellulose is studied using whole biomass in powder form. Examining the enzymatic degradation profile of individual cell types in relation to the composition and properties of their cell wall could thus help identify the parameters involved in cell wall recalcitrance.

That is why we have combined infra-red microspectrometry, mass spectrometry, fluorescence recovery after photobleaching and fluorescence imaging to investigate enzymatic hydrolysis at the cell scale in maize internode. Depending on their polymer composition and organisation, cell types exhibits different extent and rate of enzymatic degradation. Enzymes act sequentially from the cell walls rich in accessible cellulose to the most recalcitrant cells. This phenomenon can be linked to the heterogeneous distribution of enzymes in the liquid medium and the adsorption/desorption mechanisms that differ with the type of cell. This opens new path to study other biomass types/pretreatments in relation to the enzymatic activity.

This work is part of the PhD achieved by Amandine Leroy through a close collaboration between FARE lab, BIA (Nantes), BIBS platform and SOLEIL synchrotron, with funding from Région Grand Est and Grand Reims.

Read: Leroy A, Devaux M-F, Fanuel M, Chauvet H, Durand S, Alvarado C, Habrant A, Sandt C, Rogniaux H, Paës G and Guillon F. Real-time imaging of enzymatic degradation of pretreated maize internodes reveals different cell types have different profiles. Bioresource Technology 2022, 353, 127140. https://doi.org/10.1016/j.biortech.2022.127140

Contact: Dr Gabriel Paës, gabriel.paes@inrae.fr