Yongkeun+Park
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3D Visualization and Quantification of Bioplastic PHA in a Living Bacterial Cell
3D holographic microscopy leads to in-depth analysis of bacterial cells accumulating the bacterial bioplastic, polyhydroxyalkanoate (PHA)
A research team at KAIST has observed how bioplastic granule is being accumulated in living bacteria cells through 3D holographic microscopy. Their 3D imaging and quantitative analysis of the bioplastic ‘polyhydroxyalkanoate’ (PHA) via optical diffraction tomography provides insights into biosynthesizing sustainable substitutes for petroleum-based plastics.
The bio-degradable polyester polyhydroxyalkanoate (PHA) is being touted as an eco-friendly bioplastic to replace existing synthetic plastics. While carrying similar properties to general-purpose plastics such as polyethylene and polypropylene, PHA can be used in various industrial applications such as container packaging and disposable products.
PHA is synthesized by numerous bacteria as an energy and carbon storage material under unbalanced growth conditions in the presence of excess carbon sources. PHA exists in the form of insoluble granules in the cytoplasm. Previous studies on investigating in vivo PHA granules have been performed by using fluorescence microscopy, transmission electron microscopy (TEM), and electron cryotomography.
These techniques have generally relied on the statistical analysis of multiple 2D snapshots of fixed cells or the short-time monitoring of the cells. For the TEM analysis, cells need to be fixed and sectioned, and thus the investigation of living cells was not possible. Fluorescence-based techniques require fluorescence labeling or dye staining. Thus, indirect imaging with the use of reporter proteins cannot show the native state of PHAs or cells, and invasive exogenous dyes can affect the physiology and viability of the cells. Therefore, it was difficult to fully understand the formation of PHA granules in cells due to the technical limitations, and thus several mechanism models based on the observations have been only proposed.
The team of metabolic engineering researchers led by Distinguished Professor Sang Yup Lee and Physics Professor YongKeun Park, who established the startup Tomocube with his 3D holographic microscopy, reported the results of 3D quantitative label-free analysis of PHA granules in individual live bacterial cells by measuring the refractive index distributions using optical diffraction tomography. The formation and growth of PHA granules in the cells of Cupriavidus necator, the most-studied native PHA (specifically, poly(3-hydroxybutyrate), also known as PHB) producer, and recombinant Escherichia coli harboring C. necator PHB biosynthesis pathway were comparatively examined.
From the reconstructed 3D refractive index distribution of the cells, the team succeeded in the 3D visualization and quantitative analysis of cells and intracellular PHA granules at a single-cell level. In particular, the team newly presented the concept of “in vivo PHA granule density.” Through the statistical analysis of hundreds of single cells accumulating PHA granules, the distinctive differences of density and localization of PHA granules in the two micro-organisms were found. Furthermore, the team identified the key protein that plays a major role in making the difference that enabled the characteristics of PHA granules in the recombinant E. coli to become similar to those of C. necator.
The research team also presented 3D time-lapse movies showing the actual processes of PHA granule formation combined with cell growth and division. Movies showing the living cells synthesizing and accumulating PHA granules in their native state had never been reported before.
Professor Lee said, “This study provides insights into the morphological and physical characteristics of in vivo PHA as well as the unique mechanisms of PHA granule formation that undergo the phase transition from soluble monomers into the insoluble polymer, followed by granule formation. Through this study, a deeper understanding of PHA granule formation within the bacterial cells is now possible, which has great significance in that a convergence study of biology and physics was achieved. This study will help develop various bioplastics production processes in the future.”
This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries (Grants NRF-2012M1A2A2026556 and NRF-2012M1A2A2026557) and the Bio & Medical Technology Development Program (Grant No. 2021M3A9I4022740) from the Ministry of Science and ICT (MSIT) through the National Research Foundation (NRF) of Korea to S.Y.L. This work was also supported by the KAIST Cross-Generation Collaborative Laboratory project.
-PublicationSo Young Choi, Jeonghun Oh, JaeHwang Jung, YongKeun Park, and Sang Yup Lee. Three-dimensional label-free visualization and quantification of polyhydroxyalkanoates in individualbacterial cell in its native state. PNAS(https://doi.org./10.1073/pnas.2103956118)
-ProfileDistinguished Professor Sang Yup LeeMetabolic Engineering and Synthetic Biologyhttp://mbel.kaist.ac.kr/
Department of Chemical and Biomolecular Engineering KAIST
Endowed Chair Professor YongKeun ParkBiomedical Optics Laboratoryhttps://bmokaist.wordpress.com/
Department of PhysicsKAIST
2021.07.28 View 10256 -
OUIC Presents the Six Most Promising Techs Transferrable to Local SMEs
KAIST will showcase the six most promising technologies for small and medium enterprises (SMEs) on November 14 in the Academic Cultural Complex. To strengthen the competitive edge of local SMEs in Daejeon, the Office of University-Industry made a survey of their technological needs and came up with the six most promising technologies. Developers will introduce their technologies during the session.Besides the introduction of the promising technologies, the session will also provide a program named University to Business (U2B) to match up technologies according to the SMEs’ needs. SMEs who wish to engage in technology transfers can receive counseling and other support programs during the session.First, Professor Seok-Hyung Bae from the Department of Industrial Design will present a technology for controlling cooperation robots. Professor Bae inserted flexible materials between the controllers to allow robots to use both hands stably and operate more accurately and swiftly. It can be applied to automatic robots, industrial robots, and service robots.Professor Hyun Myung from the Department of Civil & Environmental Engineering will demonstrate a robot navigation system in a dynamic indoor and outdoor environment, which can be applied to robotics in logistics, smart factories, and autonomous vehicles. Providing robust simultaneous localization and mapping systems, this technology shows high-performing navigation with low-cost sensors.Meanwhile, Professor Siyoung Choi from the Department of Chemical and Biomolecular Engineering will introduce a technology for forming stable adhesive emulsions. An emulsion is a stable mixture of water and oil. Conventionally, a small amount of surfactant is added to stabilize an emulsion. Here, Professor Choi developed a stable emulsion system without using any chemical substances. This technology can be applied to various fields, including the cosmetics, pharmaceutical, semiconductor, and painting industries. The session will also present smart IoTs platform technology developed by Professor Jinhong Yang from the KAIST Institute for IT Convergence. His technology minimizes errors occurring when multiple IoT devices are connected simultaneously. Professor Yong Keun Park from the Department of Physics will introduce a technology for measuring glycated hemoglobin by using the optical properties of red blood cells. This technology can be applied to make low-cost, small-sized measuring equipment. It can also be used for vitro diagnoses including diabetes, cardiovascular disorders, tumors, kidney disease, and infectious diseases. Professor Yong Man Ro from the School of Electrical Engineering will show technology for biometric access control. Conventional technologies for face recognition fall behind other biometrics. Professor Ro and his team developed a facial dynamics interpreting network which allows very accurate facial recognition by interpreting the relationships between facial local dynamics and estimating facial traits. This technology can be applied to security and communication in finance, computers, and information system.KAIST President Sung-Chul Shin said, “KAIST will continue to support SMEs to have stronger competitiveness in the market. Through technology transfer, we will drive innovation in technological commercialization where a university’s research and development creates economic value.”
2018.11.13 View 7523 -
2017 KAIST Research Day Honors Professor Hoon Sohn
The 2017 KAIST Research Day recognized Professor Hoon Sohn of the Department of Civil and Environmental Engineering as Research Grand Prize Awardee in addition to the 10 most distinguished research achievements of the past year.
The Research Grand Prize recognizes the professor whose comprehensive research performance evaluation indicator is the highest over the past five years. The indicator combines the factors of the number of research contracts, IPR, royalty income, as well as research overhead cost inclusion.
During the ceremony, which was held on May 23, Professor Jun-Ho Oh of the Department of Mechanical Engineering and Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering also won the Best Research Award. The two professors had the best scores when evaluating their research performance for one-year periods.
Meanwhile, the Research Innovation Award went to Professor YongKeun Park of the Department of Physics. The Research Innovation Award scores the factors of foreign patent registration, contracts of technological transfer and income from technology fees, technology consultations, and startups and selected Professor Park as the top winner.
Professors Yong Hee Lee of the Department of Physics and Jonghwa Shin of the Department of Material Science won the Convergence Research Award. The Convergence Research Award recognizes the most outstanding research team who created innovative research results for a year.
After the ceremony, President Chen Shiyi of the Southern University of Science and Technology gave a distinguished lecture on the “Global & Entrepreneurial Universities for the Age of the Fourth Industrial Revolution.” the Research Day ceremony, KAIST also presented the ten most distinguished research achievements made by KAIST professors during the last year as follows (Click):
▲ Commercialization of 3D Holographic Microscopy by Professor YongKeun Park of the Department of Physics
▲ Designer Proteins with Chemical Modifications by Professor Hee-Sung Park of the Department of Chemistry
▲ Lanthanum-Catalyzed Synthesis of Microporous 3D Graphene-Like Carbons in a Zeolite Template by Professor Ryong Ryoo of the Department of Chemistry
▲ Complete Prevention of Blood Loss by Self-Sealing Hemostatic Needles by Professor Haeshin Lee of the Department of Chemistry
▲ An Immunological Mechanism for the Contribution of Commensal Microbiota Against Herpes Simplex Virus Infection in Genital Mucosa by Heung Kyu Lee of the Graduate School of Medical Science and Engineering
▲ Development of a Pulse-Echo Laser Ultrasonic Propagation Imaging System by Professor Jung-Ryul Lee of the Department of Aerospace Engineering
▲ Bi-refractive Stereo Imaging for Single-Shot Depth Acquisition by Professor Min H. Kim of the School of Computing
▲ Development of Environment Friendly Geotechnical Construction Material Using Biopolymer by Professor Gye-Chun Cho of the Department of Civil and Environmental Engineering
▲ Protein Delivery Via Engineered Exosomes by Professor Chulhee Choi of the Department of Bio and Brain Engineering
▲ Hot Electron Detection Under Catalytic Reactions by Professor Jeong Young Park of the Graduate School of EEWS.
After the ceremony, President Chen Shiyi of the Southern University of Science and Technology gave a distinguished lecture on the “Global & Entrepreneurial Universities for the Age of the Fourth Industrial Revolution.”
(Photo:President Shin poses with the 2017 KAIST Research Grand Prize Winner Professor Hoon Sohn on May 23.)
2017.05.23 View 11316