Enzymatic Modification of Plant Cell Wall Polysaccharides

Abstract

Plant cell walls are intricate structures with remarkable properties, widely used in almost every aspect of our life. Cell walls consist largely of complex polysaccharides and there is often a need for chemical and biochemical processing before industrial use. There is an increasing demand for sustainable processes that replace chemical treatments with white biotechnology. Plants can contribute significantly to this sustainable process by producing plant or microbial enzymesin plantathat are necessary for plant cell wall modification or total degradation. This will give rise to superior food fibres, hydrocolloids, paper, textile, animal feeds or biofuels. Classical microbial‐based fermentation systems could in the future face serious competition from plant‐based expression systems for enzyme production. Plant expressed enzymes can either be targeted to specific cellular compartments for accumulation and storage, or targeted to the cell wall for immediate modification of the polysaccharides. Furthermore, thermoactivated enzymes can successfully be employed to avoid undue degradation of the cell wall and detrimental phenotypes resulting from this. A further use of enzyme expressionin plantais the possibility of elucidating the biological role of specific polymers, such as the involvement of xyloglucan in tree bending, or to decrease the level of pectin in flax to simplify the retting step in the textile refinery process.

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“…Our understanding of cell wall composition, structure, and mechanics has expanded rapidly over the past decade due to advances in high-resolution imaging (Zeng et al, 2017;Rydahl et al, 2018;Voiniciuc et al, 2018;Zhao et al, 2019), biochemical and spectroscopic analyses of wall polymers and their interactions down to single-molecule and nanoscale levels (Voxeur et al, 2019;Zhao et al, 2020;Cai et al, 2021), and new computational modeling methods that relate wall mechanics to the deformations, movements, and interactions of individual wall polymers (Zhang et al, 2021). In contrast to its previous conception as simply "dead wood" that is the inert product of polymer secretion by plant cells, the plant cell wall is starting to be appreciated as a dynamic structure that changes over time and encompasses specialized metabolic processes, including the polymerization, coalescence, binding/unbinding, cleavage, and re-ligation of wall polymers that facilitates both plant growth and the processing of plant biomass for human use (Obro et al, 2011). Cell walls serve as conduits of intercellular transport of nutrients, secreted peptides, hormones, and other metabolites (Ramakrishna and Barberon, 2019), arenas where extracellular vesicles can deliver small RNAs to silence virulence genes in plant pathogens (Cai et al, 2018), and surveillance zones where plants can sense pathogen-generated wall fragments (Vaahtera et al, 2019) to help maintain wall integrity (Rui and Dinneny, 2020).…”