To grow tall and withstand high winds, plants need to be strong and flexible in just the right ways. Trees gain these properties from natural polymers in their cell walls. Cellulose is the most famous cell wall polymer, and gives the plant cell its shape and structure, while lignin gives rigidity and strength.
Lesser known components of wood are the hemicelluloses – long chain complex carbohydrates such as xylan and mannan. Hemicelluloses are often flexible and slightly soluble, so their function in the stiff and strong wood cell wall is a bit mysterious. But their properties make them valuable components in food packaging, wound dressings, and more.
New research published in Nature Communications has investigated the structural roles of hemicelluloses extracted from wood by developing a simplified model of a wood cell wall, using bacterial cellulose.
The research has illuminated the biological functions of xylan and mannan, as discussed in a Behind the Paper blog by the paper's lead author, Francisco Vilaplana. It revealed that xylan makes the cell wall more stretchy, while mannan makes it more resistant to compression. The ultimate goal of Vilaplana's research program is to inform the design and development of new bio-based materials from industrial wood waste.
In particular, Vilaplana believes this work will help material scientists find better ways of using cellulose, and said via email: “We now know that mixing cellulose with xylan makes it more extensible, which is really useful for making packaging materials, whereas adding mannan improves the compressive properties, which could be helpful in light construction materials.” This could directly inform the work of companies such as Cellutech, which are already developing cellulose-based packaging materials.
Being able to tailor the properties of naturally occurring materials is an important step to making their use economically attractive, helping us move towards an overall more sustainable bio-based industrial economy.