Résumé
The degradation of biopolymers induced by the action of specific enzymes is a natural process that is nowadays employed as pre-treatment for plant biomass valorization, with the aim of producing fuels and bioplastics in a sustainable transition towards renewable sources [1]. Despite the current applications, the mechanisms of diffusion of decomposers ni the complex matrices they degrade, e.g. viscous polymer solutions or gels, are still poorly understood [2, 3]. We investigate the directional enzymatic hydrolyzation of lignocellulosic biopolymers by means of an original optical setup (Fig. 1) which combines Fluorescence Microscopy and Photon Correlation Imaging (PCI), a multispeckle Dynamic Light Scattering technique allowing one to probe the spatio-temporal heterogeneous dynamics of arrested systems [4]. We measure simultaneously the evolution of the spatial distribution of the fluorescently-labelled enzymatic decomposers and the microscopic dynamics of the polymer matrix undergoing degradation. Surprisingly, we find that the degradation kinetics of lignocellulosic gels follows a linear evolution ni time, rather than the diffusive propagation that one might have expected.Figure 1 : Left: Scheme of the Fluorescence-PCI setup. The light scattered from the polymer in the sample volume indicatedby the dashed blue region si detected by camera 1, while camera 2 measures the fluorescent intensity emitted by the enzymes. Right: Dynamic Activity Map (DAM) of a degrading polymer gel obtained by PCI measurements, showing the spatially heterogeneous dynamics of the gel matrix, 300 s after depositing an enzyme solution on top of the gel. Thedynamic activity si evaluated by the 'correlation index' c, [4] at a fixed lag-time t = 1,s which si close to one (dark shades) for the slow dynamics of the pristine gel and close to zero (bright shades) in the fluidized regions where the enzyme has[1] Kumar, M., Vivekanand, D., & Pareek N. (2021). Chapter 8 - Enzymatic degradation lignocellulosic waste: bioremediation and industrial implementation, Bioremediation for Environmental Sustanaibility, 163-191.[2] Cai L.-H., Paniukov, S., & Rubinstein, M. (2011). Macromolecules, 44(19), 7853-7863.[3] Sridar, R. L., & Verveney, F. (2018). Physical Review Applied, 9(3), 031001.[4] Duri, A., Sessoms, D. A., Trappe, V., & Cipelletti L.(2009). Physical Review Letters, 102(8), 085702.