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Microporous cell-laden hydrogels for engineered tissue constructs
Park, Jae Hong,Chung, Bong Geun,Lee, Won Gu,Kim, Jinseok,Brigham, Mark D.,Shim, Jaesool,Lee, Seunghwan,Hwang, Chang Mo,Durmus, Naside Gozde,Demirci, Utkan,Khademhosseini, Ali Wiley Subscription Services, Inc., A Wiley Company 2010 Biotechnology and bioengineering Vol.106 No.1
<P>In this article, we describe an approach to generate microporous cell-laden hydrogels for fabricating biomimetic tissue engineered constructs. Micropores at different length scales were fabricated in cell-laden hydrogels by micromolding fluidic channels and leaching sucrose crystals. Microengineered channels were created within cell-laden hydrogel precursors containing agarose solution mixed with sucrose crystals. The rapid cooling of the agarose solution was used to gel the solution and form micropores in place of the sucrose crystals. The sucrose leaching process generated homogeneously distributed micropores within the gels, while enabling the direct immobilization of cells within the gels. We also characterized the physical, mechanical, and biological properties (i.e., microporosity, diffusivity, and cell viability) of cell-laden agarose gels as a function of engineered porosity. The microporosity was controlled from 0% to 40% and the diffusivity of molecules in the porous agarose gels increased as compared to controls. Furthermore, the viability of human hepatic carcinoma cells that were cultured in microporous agarose gels corresponded to the diffusion profile generated away from the microchannels. Based on their enhanced diffusive properties, microporous cell-laden hydrogels containing a microengineered fluidic channel can be a useful tool for generating tissue structures for regenerative medicine and drug discovery applications. Biotechnol. Bioeng. 2010; 106: 138–148. © 2010 Wiley Periodicals, Inc.</P>
Cho, Hyejeon,Jensen, Joseph B.,Blakeslee, John P.,French, Brigham S.,Lee, Hyun-chul,Lee, Young-Wook Cambridge University Press 2012 Proceedings of the International Astronomical Unio Vol.8 No.suppl289
<B>Abstract</B><P>The surface brightness fluctuation (SBF) method at near-infrared (NIR) wavelengths is a powerful tool for estimating distances to unresolved stellar systems with high precision. The IR channel of the Wide Field Camera 3 (WFC3), installed on board the <I>Hubble Space Telescope (HST)</I> in 2009, has a greater sensitivity and a wider field of view than the previous generation of <I>HST</I> IR instruments, making it much more efficient for measuring distances to early-type galaxies in the Local Volume. To take full advantage of its capabilities, we need to empirically calibrate the SBF distance method for WFC3's NIR passbands. We present the SBF measurements for the WFC3/IR F160W bandpass filter using observations of 16 early-type galaxies in the Fornax and Virgo Clusters. These have been combined with existing (<I>g</I>475-<I>z</I>850) color measurements from the Advanced Camera for Surveys Virgo and Fornax Cluster Surveys to derive a space-based <I>H</I>160-band SBF relation as a function of color. We have also compared the absolute SBF magnitudes to those predicted by evolutionary population synthesis models in order to study stellar population properties in the target galaxies.</P>
Starch based polyhydroxybutyrate production in engineered Escherichia coli.
Bhatia, Shashi Kant,Shim, Young-Ha,Jeon, Jong-Min,Brigham, Christopher J,Kim, Yong-Hyun,Kim, Hyun-Joong,Seo, Hyung-Min,Lee, Ju-Hee,Kim, Jung-Ho,Yi, Da-Hye,Lee, Yoo Kyung,Yang, Yung-Hun Springer-Verlag 2015 Bioprocess and biosystems engineering Vol.38 No.8
<P>Every year, the amount of chemosynthetic plastic accumulating in the environment is increasing, and significant time is required for decomposition. Bio-based, biodegradable plastic is a promising alternative, but its production is not yet a cost effective process. Decreasing the production cost of polyhydroxyalkanoate by utilizing renewable carbon sources for biosynthesis is an important aspect of commercializing this biodegradable polymer. An Escherichia coli strain that expresses a functional amylase and accumulate polyhydroxybutyrate (PHB), was constructed using different plasmids containing the amylase gene of Panibacillus sp. and PHB synthesis genes from Ralstonia eutropha. This engineered strain can utilize starch as the sole carbon source. The maximum PHB production (1.24?g/L) was obtained with 2?% (w/v) starch in M9 media containing 0.15?% (w/v) yeast extract and 10?mM glycine betaine. The engineered E. coli SKB99 strain can accumulate intracellular PHB up to 57.4?% of cell dry mass.</P>
양영헌,전종민,이다혜,김정호,서형민,Cho Kyun Rha,Anthony J. Sinskey,Christopher J. Brigham 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.2
Conventional solvent-based methods are still the most practical approaches for recovery of polyhydroxyalkanoate (PHA) polymer from cellular biomass, even though potential alternatives exist, including chemical, mechanical, and enzymatic methods. It is still necessary, however, to avoid dangerous and environmentally unfriendly solvents (e.g., chloroform and dichloromethane) in the polymer recovery process. In the work presented here, we applied various solvent systems to recover PHA from Ralstonia eutropha and recombinant Escherichia coli cells. It was demonstrated that methyl ethyl ketone (MEK) is a promising solvent for PHA recovery from bacterial cells, particularly for the copolymer poly(hydroxybutyrate-cohydroxyvalerate) [P(HB-co-HV)], exhibiting > 90% polymer recovery. Even though MEK did not solubilize PHAs to the same extent as chloroform, it can recover a comparable amount of polymer because of its processing advantages, such as the low viscosity of the MEK/PHA solution, and the lower density of MEK as compared to cellular components. MEK was found to be the best alternative, non-halogenated solvent among examined candidates for recovery of P(HB-co-HV) from cells. The MEK treatment of PHAcontaining cells further allowed us to eliminate several costly and lengthy steps in the extraction process, such as cell lysis, centrifugation, and filtration.
Jeon, J. M.,Kim, H. J.,Bhatia, S. K.,Sung, C.,Seo, H. M.,Kim, J. H.,Park, H. Y.,Lee, D.,Brigham, C. J.,Yang, Y. H. SPRINGER 2017 BIOPROCESS AND BIOSYSTEMS ENGINEERING Vol.40 No.5
<P>Polyhydroxyalkanoate (PHA) is a family of biodegradable polymers, and incorporation of different monomers can alter its physical properties. To produce the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) containing a high level of 3-hydroxyvalerate (3HV) by altering acetyl-CoA pool levels, we overexpressed an acetyl-CoA acetyltransferase (atoAD) in an engineered E. coli strain, YH090, carrying PHA synthetic genes bktB, phaB, and phaC. It was found that, with introduction of atoAD and with propionate as a co-substrate, 3HV fraction in PHA was increased up to 7.3-fold higher than a strain without atoAD expressed in trans (67.9 mol%). By the analysis of CoA pool concentrations in vivo and in vitro using HPLC and LC-MS, overexpression of AtoAD was shown to decrease the amount of acetyl-CoA and increase the propionyl-CoA/acetyl-CoA ratio, ultimately resulting in an increased 3HV fraction in PHA. Finally, synthesis of P(3HB-co-3HV) containing 57.9 mol% of 3HV was achieved by fed-batch fermentation of YJ101 with propionate.</P>
Discarded Egg Yolk as an Alternate Source of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate)
( Yun-gi Hong ),( Yu-mi Moon ),( Ju-won Hong ),( Tae-rim Choi ),( Hye-rim Jung ),( Soo-yeon Yang ),( Dae-won Jang ),( Ye-rim Park ),( Christopher J. Brigham ),( Jae-seok Kim ),( Yoo-kyung Lee ),( Yung 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.3
Many poultry eggs are discarded worldwide because of infection (i.e., avian flu) or presence of high levels of pesticides. The possibility of adopting egg yolk as a source material to produce polyhydroxyalkanoate (PHA) biopolymer was examined in this study. Cupriavidus necator Re2133/pCB81 was used for the production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3HHx), a polymer that would normally require long-chain fatty acids as carbon feedstocks for the incorporation of 3HHx monomers. The optimal medium contained 5% egg yolk oil and ammonium nitrate as a nitrogen source, with a carbon/nitrogen (C/N) ratio of 20. Time course monitoring using the optimized medium was conducted for 5 days. Biomass production was 13.1 g/l, with 43.7% co-polymer content. Comparison with other studies using plant oils and the current study using egg yolk oil revealed similar polymer yields. Thus, discarded egg yolks could be a potential source of PHA.