Transgenic cover plants containing hemicellulase and cellulase which degrade lignin and cellulose to fermentable sugars
First Claim
1. A method for converting lignocellulose of plant material from a cover crop with low amounts of lignin to fermentable sugars comprising:
- (a) providing a transgenic monocot plant selected from the group consisting of rice, wheat, barley, oat, triticale, and rye, the transgenic monocot plant being a low-lignin cover crop which includes (i) at least one DNA encoding a cellulase and hemicellulase which is operably linked to a nucleotide sequence encoding a signal peptide wherein the signal peptide directs the cellulase to an organelle of the transgenic plant and (ii) at least one DNA encoding a ligninase which is operably linked to a nucleotide sequence encoding a signal peptide wherein the signal peptide directs the ligninase to the organelle of the transgenic plant;
(b) growing the transgenic plant for a time sufficient for the transgenic plant to accumulate a sufficient amount of the cellulase and hemicellulase and the ligninase in the sub-cellular compartments of the transgenic plant;
(c) harvesting the transgenic plant which has accumulated the cellulase, hemicellulase and ligninase in the sub-cellular compartments of the transgenic plant;
(d) grinding the transgenic plant for a time sufficient to produce the plant material wherein the cellulase, hemicellulase and ligninase produced by the transgenic plant are released from organelle and cell wall areas of the transgenic plant;
(e) incubating the plant material for a time sufficient for the cellulase, hemicellulase and ligninase in the plant material to produce the fermentable sugars and lignin deconstructed by the ligninase from the lignocellulose in the plant material; and
(f) extracting the fermentable sugars produced from the cellulose and hemicelluloses by the cellulase and hemicellulase from the plant material.
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Abstract
The present invention provides transgenic cover crop plants which after harvest degrade the hemicellulose and cellulose therein to fermentable sugars which can further be fermented to ethanol or other products. In particular, the transgenic plants comprise cellulase, hemicellulase and optionally ligninase genes from microbes operably linked to a DNA encoding a signal peptide which targets the fusion polypeptide produced therefrom to an organelle of the plant, in particular, the chloroplasts. When the transgenic plants are harvested, the plants are ground to release the hemicellulase and cellulase which then degrade the hemicellulose and cellulose of the transgenic plants to produce the fermentable sugars.
19 Citations
13 Claims
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1. A method for converting lignocellulose of plant material from a cover crop with low amounts of lignin to fermentable sugars comprising:
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(a) providing a transgenic monocot plant selected from the group consisting of rice, wheat, barley, oat, triticale, and rye, the transgenic monocot plant being a low-lignin cover crop which includes (i) at least one DNA encoding a cellulase and hemicellulase which is operably linked to a nucleotide sequence encoding a signal peptide wherein the signal peptide directs the cellulase to an organelle of the transgenic plant and (ii) at least one DNA encoding a ligninase which is operably linked to a nucleotide sequence encoding a signal peptide wherein the signal peptide directs the ligninase to the organelle of the transgenic plant; (b) growing the transgenic plant for a time sufficient for the transgenic plant to accumulate a sufficient amount of the cellulase and hemicellulase and the ligninase in the sub-cellular compartments of the transgenic plant; (c) harvesting the transgenic plant which has accumulated the cellulase, hemicellulase and ligninase in the sub-cellular compartments of the transgenic plant; (d) grinding the transgenic plant for a time sufficient to produce the plant material wherein the cellulase, hemicellulase and ligninase produced by the transgenic plant are released from organelle and cell wall areas of the transgenic plant; (e) incubating the plant material for a time sufficient for the cellulase, hemicellulase and ligninase in the plant material to produce the fermentable sugars and lignin deconstructed by the ligninase from the lignocellulose in the plant material; and (f) extracting the fermentable sugars produced from the cellulose and hemicelluloses by the cellulase and hemicellulase from the plant material. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for providing plant material from a cover crop with low amounts of lignin comprising:
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(a) growing and harvesting a first cash crop on a plot of land; (b) providing a transgenic monocot plant which is the low-lignin cover crop which includes at (i) least one DNA encoding a cellulase and hemicellulase which is operably linked to a nucleotide sequence encoding a signal peptide wherein the signal peptide directs the cellulase to an organelle of the transgenic plant and (ii) optionally at least one DNA encoding a ligninase which is operably linked to a nucleotide sequence encoding a signal peptide wherein the signal peptide directs the ligninase to the organelle of the transgenic plant; (c) growing the transgenic plant on the plot (i) during a winter season, (ii) subsequent to the harvesting of the first cash crop from the plot, and (iii) for a time sufficient for the transgenic plant to accumulate a sufficient amount of the cellulase and hemicellulase and limited amounts of the ligninase if present in the sub-cellular compartments of the transgenic plant; (d) harvesting the transgenic plant which has accumulated the cellulase, hemicellulase and ligninase if present in the sub-cellular compartments of the transgenic plant; and (e) growing and harvesting second cash crop on the plot of land subsequent to the harvesting of the transgenic plant from the plot. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification