Rice Plant Modified to Produce Cellulolytic Enzyme in Leaves Possesses Dual Food/Bioenergy Functionality

An international team of scientists from Taiwan (National Chiayi University) and the United States (Pacific Northwest National Laboratory and Washington State University) report the development of transgenic rice plants which can express high levels of a cellulolytic enzyme in its biomass, without severely impairing plant growth and development. Cellulolytic enzymes (or cellulases) are commonly used to convert cellulose molecules in pretreated plant biomass into fermentable sugars which can be further processed to produce biofuel ethanol. "The cellulose hydrolytic enzyme, β-1, 4-endoglucanase (E1) gene, from the thermophilic bacterium Acidothermus cellulolyticus,was overexpressed in rice through Agrobacterium-mediated transformation".

The researchers were able to obtain 52 transgenic plants from six independent lines which express the enzymes at high levels, without serious negative effects on plant development. Some transgenic plants, however had "shorter stature and flowered earlier than the wild type". The enzyme was also shown to be thermostable,with high substrate specificity for cellulose, and can be easily purified by simple heat treatment. When the transgenic rice straw was cultured with cow gastric fluid for one hour at 39^oC (and another hour at 81 ^oC), it was hydrolysed more easily compared to the wild type rice straw, producing 43% more reducing sugars. The results of the study suggest that the transgenic rice plant can be used as a "multi-functional plant", where the grains can serve as food, and the biomass can be used as an effective bioenergy feedstock, or as an industrial source of cellulases. The full study is published in the open-access journal, Biotechnology for Biofuels (URL above).