Fiber foods

The secret of the structure of plant dietary fibers revealed

The secret of how fibers shape the structure of plant cell walls has been revealed, with potentially wide-ranging applications ranging from nutrition and health to agriculture.

Researchers from the University of Queensland and the KTH Royal Institute of Technology in Sweden have uncovered the mechanisms of how plant cell walls balance the strength and stiffness provided by cellulose with its ability to stretch and compress .

UQ director of the Center for Nutrition and Food Sciences, Professor Mike Gidley, said the team had identified that a family of cell wall polymers – hemicelluloses – play a critical role in balancing the need rigidity and the flexibility to bend without breaking.

“This finding is important for understanding the properties of dietary fiber in nutrition, but also for applications in medicine, agriculture and a range of other industries,” Prof Gidley said.

“Plants have no skeletons, and their structures can range from soft, flexible grasses to the majestic architecture of a eucalyptus, with the main differences being in the fiber structure of their cell walls.”

The diversity of plant structures results from the three basic building blocks of plant fiber – cellulose, hemicellulose and lignins – in plant cell walls.

“Lignins provide the waterproofing of wood fibers and cellulose is the rigid scaffolding material in almost all plant types, but the mechanical function of hemicellulose was a mystery,” Professor Gidley said.

Professor Gidley and Dr Deirdre Mikkelsen, together with Dr Francisco Vilaplana of KTH’s Wallenberg Wood Science Center, have experimented with two major components of hemicellulose – with dramatic effect.

“We tested the properties of cellulose when adding different proportions of the two components and found that ‘mannans’ improved compression while ‘xylans’ significantly increased its elasticity,” Dr. Mikkelsen said.

“We generated a modified cellulosic material in the lab that could be stretched to twice its length at rest, which is like watching a wet sheet of paper stretch to double its length without tearing.”

The team said their discovery had many applications, including in wound care and in the texture of plant foods.

“This information is also valuable for gut microbiome research to better understand how plant cell walls, or fibers, break down in the gut,” Prof Gidley said.

“Complex plant fiber is already processed for low-value applications, but high-value materials are typically made from pure (bacterial) cellulose.

“Our work creates the basis for new cellulose chemistry in which xylans and mannans are added to make composites with useful properties.

“This means new possibilities for developing better, environmentally friendly plant-based materials, as well as for breeding natural plant fibers with desirable properties in agriculture and food.”

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