Mechanical Properties of Genetically Engineered Young Aspen with Modified Lignin Content and/or Structure

Abstract

Reducing lignin content is a target for processes such as papermaking because lignin removal requires a tremendous amount of energy and chemicals. Recent advances in tree genetics permit modification of lignin content and structure. The consequences of lignin modifications on many wood properties are not known. The purpose of this study was to establish the effect of genetic modification of lignin on selected wood mechanical properties. In this study, genetically modified young quaking aspen trees with reduced lignin content and/or increased syringyl to guaiacyl (S/G) ratio were investigated and compared with the wild type. The modulus of elasticity in three-point bending and the compression strength parallel to the grain were measured using modified micromechanical tests. The results indicate that the genetic modification used in this study had a negative effect on these mechanical properties. The transgenic trees with reduced lignin content showed a severe reduction in modulus of elasticity and compression strength parallel to the grain, whereas the transgenic trees with increased S/G ratio had only a slight decrease in these properties compared with the wild type. The simultaneous modification of lignin content and S/G ratio shows inconsistent results and needs further investigation.