Title: Engineering E. coli for simultaneous glucose–xylose utilization during methyl ketone production

Abstract

Previously, we developed an E. coli strain that overproduces medium-chain methyl ketones for potential use as diesel fuel blending agents or as flavors and fragrances. To date, the strain's performance has been optimized during growth with glucose. However, lignocellulosic biomass hydrolysates also contain a substantial portion of hemicellulose-derived xylose, which is typically the second most abundant sugar after glucose. Commercialization of the methyl ketone-producing technology would benefit from the increased efficiency resulting from simultaneous, rather than the native sequential (diauxic), utilization of glucose and xylose. In this study, genetic manipulations were performed to alleviate carbon catabolite repression in our most efficient methyl ket one-producing strain. A strain engineered for constitutive expression of xylF and xylA (involved in xylose transport and metabolism) showed synchronized glucose and xylose consumption rates. However, this newly acquired capability came at the expense of methyl ketone titer, which decreased fivefold. Further efforts were made to improve methyl ketone production in this strain, and we found that two strategies were effective at enhancing methyl ketone titer: (1) chromosomal deletion of pgi (glucose-6-phosphate isomerase) to increase intracellular NADPH supply and (2) downregulation of CRP (cAMP receptor protein) expression by replacement of the native RBS with an RBS chosenmore » based upon mutant library screening results. Combining these strategies resulted in the most favorable overall phenotypes for simultaneous glucose-xylose consumption without compromising methyl ketone titer at both 1 and 2% total sugar concentrations in shake flasks. This work demonstrated a strategy for engineering simultaneous utilization of C₆ and C₅ sugars in E. coli without sacrificing production of fatty acid-derived compounds.« less

Authors:

Wang, Xi; Goh, Ee-Been; Beller, Harry R.

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• Search DOE PAGES for ORCID "0000-0001-9637-3650"

Publication Date:

Sat Jan 27 00:00:00 EST 2018

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1618887

Alternate Identifier(s):

OSTI ID: 1433113; OSTI ID: 1502853

Report Number(s):

LBNL-CRADA-20001187
Journal ID: ISSN 1475-2859; 12; PII: 862

Grant/Contract Number:  

SC0015093; AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Microbial Cell Factories

Additional Journal Information:

Journal Name: Microbial Cell Factories Journal Volume: 17 Journal Issue: 1; Journal ID: ISSN 1475-2859

Publisher:

Springer Science + Business Media

Country of Publication:

United Kingdom

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 10 SYNTHETIC FUELS; Carbon catabolite repression; Methyl ketones; NADPH; cAMP receptor protein; Metabolic engineering