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Advances made in xylan extraction for cellulosic biofuels

A newly identified gene found in rice could be the key that will allow for the use of xylan – a component of plant cell walls – in the biofuel production process, opening up possibilities.

Xylan is one of the most abundant biomass materials on earth – after cellulose. But xylan content can pose a problem to the biofuel manufacturing process as it has to be removed in order to get to the sugars needed to make biofuels.

Now, researchers with the United State’s Department of Energy’s Joint BioEnergy Institute believe that they have found a way to make xylan more extractable to increase saccharification or the breakdown of carbohydrates into releasable sugars.

They found that a gene called XAX1 acts to make xylan less extractable from plant cell walls. Working with a mutant variety of rice with the XAX1 gene removed, they found xylan was more extractable and saccharification was improved by over 60 percent.

According to Henrik Scheller, head of the institute’s feedstocks division and director of the cell wall biosynthesis group, XAX1 is the first enzyme known to be specific to grass xylan synthesis.

By showing that xylan can be modified, the findings could provide new insights into the process and into how xylan substitutions may be modified for increased biofuel generation.

Xylan is believed to play an essential structural role in plant cell walls through cross-linking interactions with cellulose and other cell wall components.

According to Pamela Ronald, who also worked on the study, xylan inhibits access of the enzymes that break down cellulose into sugars. It is also an additional substrate for cross-linking to lignin.

The rice plants without a functioning XAX1 gene had fewer cross-links with lignin, which made the xylan more extractable and also increased saccharification.

Advanced biofuels synthesized from biomass in grasses and other non-food plants have the potential to replace fossil fuels. Unlike biofuels made from corn or sugarcane, advance biofuels are renewable and carbon-neutral and do not compete for resources from the food production sector.

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