1-04: Transgenic Expression of Endoglucanase and Xylanase Genes Increases Tobacco Digestibility and Biomass Conversion

The objective of this project was to test the processing performance of transgenic feedstocks expressing cell wall hydrolyzing enzymes and to identify ways to exploit the properties of these plants during biorefining to improve conversion efficiency.  Transgenic tobacco lines expressing an endoglucanase, E1, from Acidothermus cellulolyticus and a xylananse, Xyn Z, from Clostridium thermocellum as single enzymes or transgenic tobacco expressing both enzymes were tested using dilute acid pretreatment and enzyme hydrolysis, as well as in vitro dry matter digestibility analysis, to evaluate their performance as value-added cellulosic ethanol feedstocks.   Compared to wild-type tobacco, transgenic lines displayed greater digestibility and glucan conversion when biomass was digested with commercial enzyme cocktails.   These properties were further enhanced by incubating the slurried biomass at moderate temperatures prior to hydrolysis with commercial enzyme cocktails.  These results demonstrate that transgenic crop feedstocks have potential to improve the efficiency and lower the cost of existing bioprocessing regimes by reducing enzyme loading, and point to the possibility of further modifying bioprocessing to exploit the properties of transgenic feedstocks.  This project was supported by grant 0810640 from the National Science Foundation.