GENETIC MODIFICATION OF LIGNOCELLULOSIC BIOMASS FOR INCREASING SACCHARIFICATION EFFICIENCY IN POPLARS

Lignin is the second most abundant biopolymer present in vascular plants. Lignification was one of the processes that allowed plants to flourish in terrestrial habitats. Lignification occurs in the secondary cell wall of tracheary elements and xylary fibers for maintaining a strong water conduction system and structural support to the plant. Apart from structural support, secondary cell walls also provide abundant, renewable and affordable biomass for production of biofuels. Genetic modification of lignocellulosic biomass present in secondary cell walls is an important strategy for improving bioethanol production. However, recalcitrance of secondary cell wall biomass hinders the release of simple sugars (saccharification) due to the complex nature of secondary cell wall. Therefore, it is necessary to understand the genetic mechanism regulating secondary cell wall biosynthesis in bioenergy plants like poplar trees. This study was performed to investigate how lignin alteration in the secondary cell walls affects wood properties influencing efficiency of saccharification. We genetically manipulated expression of phenyl-oxidase genes encoding some lignin-specific laccases and peroxidases present in the secondary cell walls driven by developing xylem-tissue specific promoter, DX15. We also genetically manipulated KNAT7 transcription factor that controls secondary cell wall formation under DX15 promoter to understand the impact of such modification on chemical properties of woody materials. Consequently, we produced hundreds of transgenic poplar plants with increased saccharification efficiency without compromising the plant growth and biomass production. Therefore, we report here some novel genetic manipulation strategies for increasing saccharification efficiency of lignocellulosic biomass in poplars