Yeast expressing saccharolytic enzymes for consolidated bioprocessing using starch and cellulose

摘要

The present invention is directed to a yeast strain, or strains, secreting a full suite, or any subset of that full suite, of enzymes to hydrolyze corn starch, corn fiber, lignocellulose, (including enzymes that hydrolyze linkages in cellulose, hemicellulose, and between lignin and carbohydrates) and to utilize pentose sugars (xylose and arabinose). The invention is also directed to the set of proteins that are well expressed in yeast for each category of enzymatic activity. The resulting strain, or strains can be used to hydrolyze starch and cellulose simultaneously. The resulting strain, or strains can be also metabolically engineered to produce less glycerol and uptake acetate. The resulting strain, or strains can also be used to produce ethanol from granular starch without liquefaction. The resulting strain, or strains, can be further used to reduce the amount of external enzyme needed to hydrolyze a biomass feedstock during an Simultaneous Saccharification and Fermentation (SSF) process, or to increase the yield of ethanol during SSF at current saccharolytic enzyme loadings. In addition, multiple enzymes of the present invention can be co-expressed in cells of the invention to provide synergistic digestive action on biomass feedstock. In some aspects, host cells expressing different heterologous saccharolytic enzymes can also be co-cultured together and used to produce ethanol from biomass feedstock.

主权项

1. A recombinant yeast host cell comprising
a heterologous polynucleotide encoding a polypeptide comprising an amino acid sequence at least 90% identical to the amino acid sequence of SEQ ID NO: 445; wherein the recombinant yeast host cell expresses the polypeptide; wherein the recombinant yeast host cell produces at least about 0.5 g of ethanol per hour per liter at 32.degree. C. on a substrate of corn mash, corn flour or a combination thereof; and wherein the recombinant yeast host cell is capable of producing ethanol at a rate at least equivalent to an otherwise identical yeast host cell not expressing a polypeptide at least 90% identical to SEQ ID NO: 445 when the otherwise identical host cell is provided 0.3 AGU/g solids of exogenous glucoamylase.