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Title: Cofactor engineering of ketol-acid reductoisomerase (IlvC) and alcohol dehydrogenase (YqhD) improves the fusel alcohol yield in algal protein anaerobic fermentation

Journal Article · · Algal Research
 [1];  [1];  [1];  [1]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
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Recently the feasibility of conversion of algal protein to mixed alcohols has been demonstrated with an engineered E.coli strain, enabling comprehensive utilization of the biomass for biofuel applications. However, the yield and titers of mixed alcohol production must be improved for market adoption. A major limiting factor for achieving the necessary yield and titer improvements is cofactor imbalance during the fermentation of algal protein. To resolve this problem, a directed evolution approach was applied to modify the cofactor specificity of two key enzymes (IlvC and YqhD) from NADPH to NADH in the mixed alcohol metabolic pathway. Using high throughput screening, more than 20 YqhD mutants were identified to show activity on NADH as a cofactor. Of these 20 mutants, the top five of YqhD mutants were selected for combination with two IlvC mutants with NADH as a cofactor for the modification of the protein conversion strain. The combination of the IlvC and YqhD mutants yielded a refined E.coli strain, subtype AY3, with increased fusel alcohol yield of ~60% compared to wild type under anaerobic fermentation on amino acid mixtures. When applied to real algal protein hydrolysates, the strain AY3 produced 100% and 38% more total mixed alcohols than the wild type strain on two different algal hydrolysates, respectively. The results indicate that cofactor engineering is a promising approach to improve the feasibility of bioconversion of algal protein into mixed alcohols as advanced biofuels.

Research Organization:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
AC04-94AL85000; ACO4-94AL85000; 26336
OSTI ID:
1338336
Alternate ID(s):
OSTI ID: 1402509
Report Number(s):
SAND2016-2002J; PII: S2211926416302715
Journal Information:
Algal Research, Vol. 19, Issue C; ISSN 2211-9264
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 12 works
Citation information provided by
Web of Science

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Cited By (2)

Bioconversion of distillers’ grains hydrolysates to advanced biofuels by an Escherichia coli co-culture journal November 2017
Characterization of four endophytic fungi as potential consolidated bioprocessing hosts for conversion of lignocellulose into advanced biofuels journal January 2017

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Related Subjects

59 BASIC BIOLOGICAL SCIENCES
directed evolution
isobutanol
2/3-methyl butanol
algae protein bioconversion
cofactor engineering
algal biofuel