Cofactor engineering of ketol-acid reductoisomerase (IlvC) and alcohol dehydrogenase (YqhD) improves the fusel alcohol yield in algal protein anaerobic fermentation
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
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
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