Expression of biologically active Acidothermus cellulolyticus endoglucanase in transgenic maize plants

Commercial production of ethanol from plant biomass sources employs enzymatic hydrolysis of cellulose to glucose. Transgenic plants that can produce their own hydrolysis enzymes may offer an inexpensive and convenient system for the large-scale production of these enzymes. The catalytic domain of an endo-1,4-β-d-glucanase gene from the eubacterium, Acidothermus cellulolyticus, was transferred to maize using particle bombardment, and transgenic plants were regenerated from five independent experiments containing E1 catalytic domain (E1-cd). Several of these plants grown in the greenhouse reached maturity and set seeds. Stable integration of the transgene in the genome of these plants was confirmed by Southern blot and expression of the transgene in plants by Western blot analysis. Expression of the recombinant E1-cd varied in different transgenic plants and the protein was enzymatically active. The activity-based assays indicate that the enzyme accumulated to concentrations up to 2.1% of plant total soluble proteins with enzymatic activity of 0.845 nmol/μg/min in leaf, and 2.08% with enzymatic activity of 0.835 nmol/μg/min in root tissues. The present data demonstrate the feasibility to produce a bacterial cellulase within the maize biomass crop for possible biomass conversion into fermentable sugars.