Production potential of cellulose nanofibrils from transgenic trees with reduced expression of cellulose synthase interacting 1

Cellulose nanofibrils can be derived from the native load-bearing cellulose microfibrils in wood. These microfibrils are synthesized by a cellulose synthase enzyme complex residing in the plasma membrane of developing wood cells. In addition to the cellulose synthase complex several other proteins, including cellulose synthase interacting 1 (CSI1), facilitate cellulose biosynthesis. It was previously shown that transgenic hybrid aspen trees with reduced expression of CSI1 exhibit changes in wood mechanics and cellulose microfibril properties. We hypothesized that these changes in native cellulose may impact the quality of corresponding nanofibrils. To investigate this hypothesis wood from wild type and transgenic trees with reduced expression of CSI1 was subjected to oxidative nanofibril isolation processes. The transgenic wood extracted nanofibrils exhibited a significantly lower suspension viscosity and estimated surface area. Furthermore, the manufactured nanofibril networks exhibited a higher stiffness, reduced water-uptake, tensile strength, strain-to-break and degree of polymerization compared to wild type derived nanofibrils. It was concluded that the difference in wood properties caused by decreased expression of CSI1 gave rise to nanofibrils with distinctive qualities. The observed changes in the physicochemical properties suggest that the differences are caused by changes in apparent nanofibril aspect ratio and surface accessibility. This study demonstrates the possibility to influence wood derived nanofibril quality through genetic engineering of trees and opens for breeding of wood properties for extraction of nanomaterials with defined characteristics.