Community Research and Development Information Service - CORDIS

Digesting plant cell walls for biofuel production

Releasing tightly bound carbohydrates from biomass will facilitate efficient biofuel production. Scientists deleted and inserted DNA into gene sequences that code for degradative enzymes to develop novel and improved functionalities.
Digesting plant cell walls for biofuel production
Plant-derived biomass from agricultural waste, the forestry industry or energy crops is a valuable source of renewable energy. Its energy utility is found in the rich source of carbohydrates that make up the plant cell wall. These sugars can be fermented to produce ethanol, methanol or other added value compounds.

Cellulose, hemicellulose and lignin (lignocelluloses) are the main constituents of the plant cell wall. Unfortunately, extracting or releasing the carbohydrates (cellulose and hemicellulose) from the lignin with which they are tightly bound is no easy task. The lack of degradative enzymes impedes the exploitation of these carbohydrates in biomass for optimum fuel production.

Scientists investigated the potential of genetic insertions and deletions (indels) in degradative enzymes to enable functional modifications that enhance efficacy and selectivity with EU funding of the project 'Directed evolution and semi-rational engineering of plant cell wall-degrading enzymes' (DEGRADEPLANT). Major focus was placed on developing techniques to generate libraries of indel variants through random mutagenesis. Researchers then turned their attention to directed evolution of two classes of enzymes, glycoside hydrolases and so-called promiscuous enzymes, which show broad substrate specificity.

DEGRADEPLANT investigators developed a novel experimental approach to generate indel libraries. Restriction enzymes and transposons were used to remove a certain DNA sequence and replace it with indel sequences. Scientists were able to create random variant libraries of a promiscuous bi-functional hydrolase that acts on both cellulose and xylan, two major components of lignocellulosic biomass. To date, the team has identified a number of regions in indel variants that either increase enzyme activity or give them novel functionality.

Investigators successfully developed and demonstrated the utility of their experimental technique in lignocellulosic biomass degradation. Outcomes should provide a major boost to the plant-based biomass sector provided that costs can be reduced while increasing efficiency of conversion.

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