Intelligent+Synthetic+Biology+Center
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Metabolically engineered E. coli producing phenol
Many chemicals we use in everyday life are derived from fossil resources. Due to the increasing concerns on the use of fossil resources, there has been much interest in producing chemicals from renewable resources through biotechnology.
Phenol is an important commodity chemical, and is a starting material for the production of numerous industrial chemicals and polymers, including bisphenol A and phenolic resins, and others. At present, the production of phenol entirely depends on the chemical synthesis from benzene, and its annual production exceeds 8 million tons worldwide. Microbial production of phenol seems to be a non-viable process considering the high toxicity of phenol to the cell.
In the paper published online in Biotechnology Journal, a Korean research team led by Distinguished Professor Sang Yup Lee at the Department of Chemical and Biomolecular Engineering from the Korea Advanced Institute of Science and Technology (KAIST) reported the successful development of an engineered Escherichia coli (E. coli) strain which can produce phenol from glucose. E. coli has been a workhorse for biological production of various value-added compounds such as succinic acid and 1,4-butanediol in industrial scale. However, due to its low tolerance to phenol, E. coli was not considered a viable host strain for the biological production of phenol.
Professor Lee"s team, a leading research group in metabolic engineering, noted the genetic and physiological differences of various E. coli strains and investigated 18 different E. coli strains with respect to phenol tolerance and engineered all of the 18 strains simultaneously. If the traditional genetic engineering methods were used, this work would have taken years to do. To overcome this challenge, the research team used synthetic small RNA (sRNA) technology they recently developed (Nature Biotechnology, vol 31, pp 170-174, 2013). The sRNA technology allowed the team to screen 18 E. coli strains with respect to the phenol tolerance, and the activities of the metabolic pathway and enzyme involved in the production of phenol. The research team also metabolically engineered the E. coli strains to increase carbon flux toward phenol and finally generated an engineered E. coli strain which can produce phenol from glucose.
Furthermore, the team developed a biphasic extractive fermentation process to minimize the toxicity of phenol to E. coli cells. Glycerol tributyrate was found to have low toxicity to E. coli and allowed efficient extraction of phenol from the culture broth. Through the biphasic fed-batch fermentation using glycerol tributyrate as an in situ extractant, the final engineered E. coli strain produced phenol to the highest titer and productivity reported (3.8 g/L and 0.18 g/L/h, respectively). The strategy used for the strain development and the fermentation process will serve as a framework for metabolic engineering of microorganisms for the production of toxic chemicals from renewable resources.
This work was supported by the Intelligent Synthetic Biology Center through the Global Frontier Project (2011-0031963) of the Ministry of Science, ICT & Future Planning through the National Research Foundation of Korea.
Process of Phenol Production
2013.11.05 View 9294 -
Production of chemicals without petroleum
Systems metabolic engineering of microorganisms allows efficient production of natural and non-natural chemicals from renewable non-food biomass
In our everyday life, we use gasoline, diesel, plastics, rubbers, and numerous chemicals that are derived from fossil oil through petrochemical refinery processes. However, this is not sustainable due to the limited nature of fossil resources. Furthermore, our world is facing problems associated with climate change and other environmental problems due to the increasing use of fossil resources. One solution to address above problems is the use of renewable non-food biomass for the production of chemicals, fuels and materials through biorefineries. Microorganisms are used as biocatalysts for converting biomass to the products of interest. However, when microorganisms are isolated from nature, their efficiencies of producing our desired chemicals and materials are rather low. Metabolic engineering is thus performed to improve cellular characteristics to desired levels. Over the last decade, much advances have been made in systems biology that allows system-wide characterization of cellular networks, both qualitatively and quantitatively, followed by whole-cell level engineering based on these findings. Furthermore, rapid advances in synthetic biology allow design and synthesis of fine controlled metabolic and gene regulatory circuits. The strategies and methods of systems biology and synthetic biology are rapidly integrated with metabolic engineering, thus resulting in "systems metabolic engineering".
In the paper published online in Nature Chemical Biology on May 17, Professor Sang Yup Lee and his colleagues at the Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea present new general strategies of systems metabolic engineering for developing microorganisms for the production of natural and non-natural chemicals from renewable biomass. They first classified the chemicals to be produced into four categories based on whether they have thus far been identified to exist in nature (natural vs. nonnatural) and whether they can be produced by inherent pathways of microorganisms (inherent, noninherent, or created): natural-inherent, natural-noninherent, non-natural-noninherent, and non-natural-created ones. General strategies for systems metabolic engineering of microorganisms for the production of these chemicals using various tools and methods based on omics, genome-scale metabolic modeling and simulation, evolutionary engineering, synthetic biology are suggested with relevant examples. For the production of non-natural chemicals, strategies for the construction of synthetic metabolic pathways are also suggested. Having collected diverse tools and methods for systems metabolic engineering, authors also suggest how to use them and their possible limitations.
Professor Sang Yup Lee said "It is expected that increasing number of chemicals and materials will be produced through biorefineries. We are now equipped with new strategies for developing microbial strains that can produce our desired products at very high efficiencies, thus allowing cost competitiveness to those produced by petrochemical refineries."
Editor of Nature Chemical Biology, Dr. Catherine Goodman, said "It is exciting to see how quickly science is progressing in this field – ideas that used to be science fiction are taking shape in research labs and biorefineries. The article by Professor Lee and his colleagues not only highlights the most advanced techniques and strategies available, but offers critical advice to progress the field as a whole."
The works of Professor Lee have been supported by the Advanced Biomass Center and Intelligent Synthetic Biology Center of Global Frontier Program from the Korean Ministry of Education, Science and Technology through National Research Foundation.
Contact: Dr. Sang Yup Lee, Distinguished Professor and Dean, KAIST, Daejeon, Korea (leesy@kaist.ac.kr, +82-42-350-3930)
2012.05.23 View 11744