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Modular design of metabolic network for robust production of n-butanol from galactose-glucose mixtures.

Lim HG, Lim JH, Jung GY - Biotechnol Biofuels (2015)

Bottom Line: Specifically, the engineered strain showed dramatically increased n-butanol production (3.3-fold increased to 6.2 g/L after 48-h fermentation) compared to the parental strain (1.9 g/L) in galactose-supplemented medium.Collectively, modular pathway engineering of metabolic network can be an effective approach in strain development for optimal biofuel production with cost-effective fermentable sugars.Moreover, robust production of n-butanol with sugar mixtures with variable composition would facilitate the economic feasibility of the microbial process using a mixture of sugars from cheap biomass in the near future.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Pohang, 37673 Gyeongbuk Korea.

ABSTRACT

Background: Refactoring microorganisms for efficient production of advanced biofuel such as n-butanol from a mixture of sugars in the cheap feedstock is a prerequisite to achieve economic feasibility in biorefinery. However, production of biofuel from inedible and cheap feedstock is highly challenging due to the slower utilization of biomass-driven sugars, arising from complex assimilation pathway, difficulties in amplification of biosynthetic pathways for heterologous metabolite, and redox imbalance caused by consuming intracellular reducing power to produce quite reduced biofuel. Even with these problems, the microorganisms should show robust production of biofuel to obtain industrial feasibility. Thus, refactoring microorganisms for efficient conversion is highly desirable in biofuel production.

Results: In this study, we engineered robust Escherichia coli to accomplish high production of n-butanol from galactose-glucose mixtures via the design of modular pathway, an efficient and systematic way, to reconstruct the entire metabolic pathway with many target genes. Three modular pathways designed using the predictable genetic elements were assembled for efficient galactose utilization, n-butanol production, and redox re-balancing to robustly produce n-butanol from a sugar mixture of galactose and glucose. Specifically, the engineered strain showed dramatically increased n-butanol production (3.3-fold increased to 6.2 g/L after 48-h fermentation) compared to the parental strain (1.9 g/L) in galactose-supplemented medium. Moreover, fermentation with mixtures of galactose and glucose at various ratios from 2:1 to 1:2 confirmed that our engineered strain was able to robustly produce n-butanol regardless of sugar composition with simultaneous utilization of galactose and glucose.

Conclusions: Collectively, modular pathway engineering of metabolic network can be an effective approach in strain development for optimal biofuel production with cost-effective fermentable sugars. To the best of our knowledge, this study demonstrated the first and highest n-butanol production from galactose in E. coli. Moreover, robust production of n-butanol with sugar mixtures with variable composition would facilitate the economic feasibility of the microbial process using a mixture of sugars from cheap biomass in the near future.

No MeSH data available.


Related in: MedlinePlus

a Time-course of cellular growth and galactose consumption profiles of the parental (JHL59, open symbol) and engineered (GAL_059, closed symbol) strains in galactose supplemented minimal M9 medium for 14 h. The lefty-axis represents OD600 in log scale and the righty-axis represents galactose concentration (g/L). The x-axis represents time in culture (h). Both the maximum specific growth rate (b) and the maximum specific sugar uptake rate (c) were higher in case of the engineered strain (GAL_059). The error bars indicate standard deviations of measurements from two independent cultures. Symbols: circle OD600; rectangle galactose
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Fig2: a Time-course of cellular growth and galactose consumption profiles of the parental (JHL59, open symbol) and engineered (GAL_059, closed symbol) strains in galactose supplemented minimal M9 medium for 14 h. The lefty-axis represents OD600 in log scale and the righty-axis represents galactose concentration (g/L). The x-axis represents time in culture (h). Both the maximum specific growth rate (b) and the maximum specific sugar uptake rate (c) were higher in case of the engineered strain (GAL_059). The error bars indicate standard deviations of measurements from two independent cultures. Symbols: circle OD600; rectangle galactose

Mentions: The E. coli GAL_059 strain was aerobically cultivated to evaluate its metabolic capacity when grown in M9 minimal medium containing galactose as a sole carbon source (Fig. 2a). As expected, the engineered strain showed a 37.2 % higher specific growth rate and a 66.4 % improvement in specific sugar uptake rate (Fig. 2b, c). The higher sugar uptake rate by the engineered strain resulted in the depletion of the galactose supplement in the medium within 14 h. In contrast, the parental strain JHL61 consumed about 60 % of the initial galactose.Fig. 2


Modular design of metabolic network for robust production of n-butanol from galactose-glucose mixtures.

Lim HG, Lim JH, Jung GY - Biotechnol Biofuels (2015)

a Time-course of cellular growth and galactose consumption profiles of the parental (JHL59, open symbol) and engineered (GAL_059, closed symbol) strains in galactose supplemented minimal M9 medium for 14 h. The lefty-axis represents OD600 in log scale and the righty-axis represents galactose concentration (g/L). The x-axis represents time in culture (h). Both the maximum specific growth rate (b) and the maximum specific sugar uptake rate (c) were higher in case of the engineered strain (GAL_059). The error bars indicate standard deviations of measurements from two independent cultures. Symbols: circle OD600; rectangle galactose
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4559943&req=5

Fig2: a Time-course of cellular growth and galactose consumption profiles of the parental (JHL59, open symbol) and engineered (GAL_059, closed symbol) strains in galactose supplemented minimal M9 medium for 14 h. The lefty-axis represents OD600 in log scale and the righty-axis represents galactose concentration (g/L). The x-axis represents time in culture (h). Both the maximum specific growth rate (b) and the maximum specific sugar uptake rate (c) were higher in case of the engineered strain (GAL_059). The error bars indicate standard deviations of measurements from two independent cultures. Symbols: circle OD600; rectangle galactose
Mentions: The E. coli GAL_059 strain was aerobically cultivated to evaluate its metabolic capacity when grown in M9 minimal medium containing galactose as a sole carbon source (Fig. 2a). As expected, the engineered strain showed a 37.2 % higher specific growth rate and a 66.4 % improvement in specific sugar uptake rate (Fig. 2b, c). The higher sugar uptake rate by the engineered strain resulted in the depletion of the galactose supplement in the medium within 14 h. In contrast, the parental strain JHL61 consumed about 60 % of the initial galactose.Fig. 2

Bottom Line: Specifically, the engineered strain showed dramatically increased n-butanol production (3.3-fold increased to 6.2 g/L after 48-h fermentation) compared to the parental strain (1.9 g/L) in galactose-supplemented medium.Collectively, modular pathway engineering of metabolic network can be an effective approach in strain development for optimal biofuel production with cost-effective fermentable sugars.Moreover, robust production of n-butanol with sugar mixtures with variable composition would facilitate the economic feasibility of the microbial process using a mixture of sugars from cheap biomass in the near future.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Pohang, 37673 Gyeongbuk Korea.

ABSTRACT

Background: Refactoring microorganisms for efficient production of advanced biofuel such as n-butanol from a mixture of sugars in the cheap feedstock is a prerequisite to achieve economic feasibility in biorefinery. However, production of biofuel from inedible and cheap feedstock is highly challenging due to the slower utilization of biomass-driven sugars, arising from complex assimilation pathway, difficulties in amplification of biosynthetic pathways for heterologous metabolite, and redox imbalance caused by consuming intracellular reducing power to produce quite reduced biofuel. Even with these problems, the microorganisms should show robust production of biofuel to obtain industrial feasibility. Thus, refactoring microorganisms for efficient conversion is highly desirable in biofuel production.

Results: In this study, we engineered robust Escherichia coli to accomplish high production of n-butanol from galactose-glucose mixtures via the design of modular pathway, an efficient and systematic way, to reconstruct the entire metabolic pathway with many target genes. Three modular pathways designed using the predictable genetic elements were assembled for efficient galactose utilization, n-butanol production, and redox re-balancing to robustly produce n-butanol from a sugar mixture of galactose and glucose. Specifically, the engineered strain showed dramatically increased n-butanol production (3.3-fold increased to 6.2 g/L after 48-h fermentation) compared to the parental strain (1.9 g/L) in galactose-supplemented medium. Moreover, fermentation with mixtures of galactose and glucose at various ratios from 2:1 to 1:2 confirmed that our engineered strain was able to robustly produce n-butanol regardless of sugar composition with simultaneous utilization of galactose and glucose.

Conclusions: Collectively, modular pathway engineering of metabolic network can be an effective approach in strain development for optimal biofuel production with cost-effective fermentable sugars. To the best of our knowledge, this study demonstrated the first and highest n-butanol production from galactose in E. coli. Moreover, robust production of n-butanol with sugar mixtures with variable composition would facilitate the economic feasibility of the microbial process using a mixture of sugars from cheap biomass in the near future.

No MeSH data available.


Related in: MedlinePlus