Seong Joon Choi

Bio: Seong Joon Choi is an academic researcher from KAIST. The author has contributed to research in topics: Fermentation & Isopropyl alcohol. The author has an hindex of 1, co-authored 1 publications receiving 209 citations.

Metabolic Engineering of Clostridium acetobutylicum ATCC 824 for Isopropanol-Butanol-Ethanol Fermentation

Abstract: Clostridium acetobutylicum naturally produces acetone as well as butanol and ethanol. Since acetone cannot be used as a biofuel, its production needs to be minimized or suppressed by cell or bioreactor engineering. Thus, there have been attempts to disrupt or inactivate the acetone formation pathway. Here we present another approach, namely, converting acetone to isopropanol by metabolic engineering. Since isopropanol can be used as a fuel additive, the mixture of isopropanol, butanol, and ethanol (IBE) produced by engineered C. acetobutylicum can be directly used as a biofuel. IBE production is achieved by the expression of a primary/secondary alcohol dehydrogenase gene from Clostridium beijerinckii NRRL B-593 (i.e., adhB-593) in C. acetobutylicum ATCC 824. To increase the total alcohol titer, a synthetic acetone operon (act operon; adc-ctfA-ctfB) was constructed and expressed to increase the flux toward isopropanol formation. When this engineering strategy was applied to the PJC4BK strain lacking in the buk gene (encoding butyrate kinase), a significantly higher titer and yield of IBE could be achieved. The resulting PJC4BK(pIPA3-Cm2) strain produced 20.4 g/liter of total alcohol. Fermentation could be prolonged by in situ removal of solvents by gas stripping, and 35.6 g/liter of the IBE mixture could be produced in 45 h.

Microbial electron transport and energy conservation - the foundation for optimizing bioelectrochemical systems.

Abstract: Microbial electrochemical techniques describe a variety of emerging technologies that use electrode–bacteria interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and the production of valuable products Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism And here also lies the key challenge A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis We analyze the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels Key compounds such as electron carriers (eg, cytochromes, ferredoxin, quinones, flavins) are identified and analyzed regarding their possible role in electrode–microbe interactions This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bioelectrochemical techniques

A comprehensive metabolic map for production of bio-based chemicals

Abstract: Production of industrial chemicals using renewable biomass feedstock is becoming increasingly important to address limited fossil resources, climate change and other environmental problems. To develop high-performance microbial cell factories, equivalent to chemical plants, microorganisms undergo systematic metabolic engineering to efficiently convert biomass-derived carbon sources into target chemicals. Over the past two decades, many engineered microorganisms capable of producing natural and non-natural chemicals have been developed. This Review details the current status of representative industrial chemicals that are produced through biological and/or chemical reactions. We present a comprehensive bio-based chemicals map that highlights the strategies and pathways of single or multiple biological reactions, chemical reactions and combinations thereof towards production of particular chemicals of interest. Future challenges are also discussed to enable production of even more diverse chemicals and more efficient production of chemicals from renewable feedstocks.

Bio-based production of C2–C6 platform chemicals

Abstract: Platform chemicals composed of 2-6 carbons derived from fossil resources are used as important precursors for making a variety of chemicals and materials, including solvents, fuels, polymers, pharmaceuticals, perfumes, and foods. Due to concerns regarding our environment and the limited nature of fossil resources, however, increasing interest has focused on the development of sustainable technologies for producing these platform chemicals from renewable resources. The techniques and strategies for developing microbial strains for chemicals production have advanced rapidly, and it is becoming feasible to develop microbes for producing additional types of chemicals, including non-natural molecules. In this study, we review the current status of the bio-based production of major C2-C6 platform chemicals, focusing on the microbial production of platform chemicals that have been used for the production of chemical intermediates, building block compounds, and polymers.