Insect Cellulase Expressed in Switchgrass Improves its Saccharification

Genetically engineered biofuel crops, such as switchgrass (Panicum virgatum L.), that produce their own cell wall-digesting cellulase enzymes could reduce costs of biofuel production. One potential source for enzyme genes is herbivorous insects that digest plant cell walls. Oak Ridge National Laboratory's Jonathan D. Willis expressed the TcEG1 cellulase from the red flour beetle (Tribolium castaneum) in swithcgrass and tested its potential in biofuel production.

The TcEG1 produced from transgenic switchgrass exhibited good endoglucanase activity. TcEG1 activity of air-dried leaves from green tissues was unchanged, but was greatly decreased when dried in a desiccant oven. Saccharification was increased in transgenic events by up to 28% and also had a 9% decrease in lignin content. Transgenic plants also produced more and narrower tillers, but  with equivalent biomass as the control.

Switchgrass overexpressing the TcEG1 gene appeared to be morphologically similar to its non-transgenic control and produced equivalent dry biomass. Therefore, we propose TcEG1 transgenics could be bred with other transgenic germplasm to yield new switchgrass with reduced recalcitrance to biofuel production.