Abstract
Marine biomasses capable of fixing carbon dioxide have attracted attention as an alternative to fossil resources for fuel and chemical production. Although a simple co-fermentation of fermentable sugars, such as glucose and galactose, has been reported from marine biomass, no previous report has discussed the fine-control of the galactose-to-glucose consumption ratio in this context. Here, we sought to finely control the galactose-to-glucose consumption ratio in the co-fermentation of these sugars using engineered Escherichia coli strains. Toward this end, we constructed E. coli strains GR2, GR2P, and GR2PZ by knocking out galRS, galRS-pfkA, and galRS-pfkA-zwf, respectively, in parent strain W3110. We found that strains W3110, GR2, GR2P, and GR2PZ achieved 0.03, 0.09, 0.12, and 0.17 galactose-to-glucose consumption ratio (specific galactose consumption rate per specific glucose consumption rate), respectively, during co-fermentation. The ratio was further extended to 0.67 by integration of a brief process optimization for initial sugar ratio using GR2P strain. The strategy reported in this study will be helpful to expand our knowledge on the galactose utilization under glucose conditions.
Highlights
Marine biomasses capable of fixing carbon dioxide have attracted attention as an alternative to fossil resources for fuel and chemical production
In an effort to finely control the galactose consumption rate in the co-fermentation of glucose and galactose using E. coli, we first constructed the galRS mutant, E. coli strain GR2 (Fig. 1 and Table 1), which was not able to produce the galactose operon repressors encoded from the galRS genes[21,22,23,24,25,26,27]
We expected that the resulting strain would consume galactose at a higher rate than the parent strain in the co-fermentation of glucose and galactose, we anticipated that this rate would still be fairly low
Summary
Marine biomasses capable of fixing carbon dioxide have attracted attention as an alternative to fossil resources for fuel and chemical production. We sought to finely control the galactose-to-glucose consumption ratio in the co-fermentation of these sugars using engineered Escherichia coli strains. Toward this end, we constructed E. coli strains GR2, GR2P, and GR2PZ by knocking out galRS, galRS-pfkA, and galRS-pfkA-zwf, respectively, in parent strain W3110. Some biobased fuels and chemicals can be produced via microbial fermentation from sustainable biomasses, such as wood and seaweed[7,8,9,10,11] In addition to such cellulosic biomasses, marine biomasses have been suggested as promising renewable resources[12], as they have the advantages of high biomass yield per unit area, high rates of carbon dioxide fixation, and natural a bundance[13]. ApR, λ‐Red recombinase under arabinose‐inducible BAD promoter, Cre‐recombinase under IPTG‐inducible 36 lacUV5 promoter, temperature sensitive origin trc promoter downstream of lox66‐cat‐lox[71] cassette
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