Thermophillic Organisms For Conversion Of Lignocellulosic Biomass To Ethanol

Abstract

Mutant thermophilic organisms that consume a variety of biomass derived substrates are disclosed herein. Strains of Thermoanaerobacterium saccharolyticum with acetate kinase and phosphotransacetylase expression eliminated are disclosed herein. Further, strain ALK1 has been engineered by site directed homologous recombination to knockout both acetic acid and lactic acid production. Continuous culture involving a substrate concentration challenge lead to evolution of ALK1, and formation of a more robust strain designated ALK2. Both organisms produce near theoretical ethanol yields without expressing pyruvate decarboxylase

Description

RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 12 / 090,745, filed Apr. 18, 2008, which is a U.S. National Phase Application of PCT / US2006 / 042442, filed Oct. 31, 2006, which claims priority to U.S. application Ser. No. 60 / 731,674, filed Oct. 31, 2005, and to U.S. application Ser. No. 60 / 796,380, filed May 1, 2006, each of which is incorporated herein by reference.GOVERNMENT INTERESTS[0002]The United States Government may have certain rights in the present invention as research relevant to its development was funded by National Institute of Standards and Technology (NIST) contract number 60NANB1D0064.BACKGROUND[0003]1. Field of the Invention[0004]The present invention pertains to the field of biomass processing to produce ethanol. In particular, novel thermophilic organisms that consume a variety of biomass derived substrates and produce ethanol in high yield are disclosed, as well as processes for the production and use of the organism...

AI Technical Summary

Benefits of technology

The present patent describes a method for producing ethanol using thermophilic, anaerobic bacteria that can consume a variety of biomass substrates and produce ethanol in high yields. The method involves knocking out genes in the bacteria that produce organic acids, resulting in higher ethanol production. The patent also describes a transformation method for eliminating genes that confer upon the bacteria the ability to produce lactic acid or acetic acid as fermentation products. The transformed bacteria are then cultured in medium containing a substrate, such as glucose or xylose, to produce ethanol. The patent also describes an isolated polynucleotide and a host cell genetically engineered to express the polynucleotide for use in the production of ethanol. Overall, the patent provides a technical solution for efficiently producing ethanol using thermophilic bacteria.

Problems solved by technology

In one such example, β-glucosidase ceases to hydrolyze cellobiose in the presence of glucose and, in turn, the build-up of cellobiose impedes cellulose degradation.

Overall, the performance of ethanol-producing organisms is compromised by production of organic products other than ethanol, and particularly by ldh-mediated conversion of pyruvate to lactate, and by conversion of acetyl-CoA to acetate by phosphotransacetylase and acetate kinase.

Although the knockout of ldh constitutes an advance in the art, it is problematic for some uses of this organism in that this strain of T. saccharolyticum continues to make organic acid—in particular, acetic acid.

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