Sweetening woody biomass

The cell walls in wood, with their abundant lignocellulose, are a vast source of renewable biomass. To make this woody biomass a usable source, however, these raw materials require conversion into simple sugars, and then further processing by microorganisms into ethanol and other bioproducts.

The major limiting factor for this process is resistance to the saccharification (conversion into the simple sugars). A complex matrix of polymers, such as pectin, make these wood cell walls inaccessible to degrading enzymes and chemicals, preventing their efficient breakdown into sugars.

In a recent study published in Biotechnology for Biofuels, Biswal and colleagues have found that aspen which over expresses pectate lyase (an enzyme that degrades pectin) is easier to breakdown into sugars. When overexpressed, the enzyme loosened several components of the wood cell wall, while not affecting overall composition. This pectin degradation increased solubility of wood polysaccharides and so the efficiency of saccharification, liberating the sugars held within.

This new study provides important new information on the processes of cell wall deconstruction. The effect of pectin degradation was previously shown to enhance saccharification in stems of herbaceous plants, but it is surprising that this should also affect aspen wood considering pectin is only a minor cell wall component.

The research also has important implications for bioenergy crops. The beneficial effect on saccharification that this study presents could be exploited to enhance the suitability of woody biomass for biofuels production. By designing a more efficient cocktail of saccharification enzymes targeting pectin, or by researching genetic engineering strategies to modify pectin structure, we could aid the industrial scale-up of biofuels production.

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