Yeast expressing saccharolytic enzymes for consolidated bioprocessing using starch and cellulose

Abstract

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 com starch, corn fiber, lignocellulose, (including enzymes that hydrolyze linkages in cellulose, hemicelhiiose, 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 togetherand used to produce ethanol from biomass feedstock.

Description

Background of the Invention [0001] Biomass is biological material from living or recently living organisms, such as wood, waste, (hydrogen) gas and alcohol fuels. Biomass is based on carbon, hydrogen and oxygen. Nitrogen and small amounts of other atoms including alkali metals, alkaline earth metals and heavy metals can also be found. Metals are commonly found in functional molecules such as porphyrins, including chlorophyll which contain magnesium. Plants specifically combine water and carbon dioxide into sugar building blocks. The required energy is generated from light by chlorophyll-based photosynthesis. On average, 0.1 to 1% of the available light is stored in plants as chemical energy. Sugar building blocks are the starting point for all major fractions, lignin, hemicellulose and cellulose found in land plants. Biomass is widely recognized as a promising source of feedstock for the production of renewable fuels and chemicals. A major obstacle to more widespread ene...

AI Technical Summary

Problems solved by technology

U.S. Patent No. 5,422,267 discloses the use of glucoamylase in yeast for the production of alcoholic beverages; however, the commercially relevant potency of ethanol is not disclosed

[0026] Furthermore, although yeast cells are known to naturally utilize sugars such as glucose and mannose, they lack the ability to efficiently utilize pentoses such as xylose and arabinose

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