Guro Gu, South Korea
Guro Gu, South Korea

Time filter

Source Type

Dooley K.,Columbia University | Kim Y.H.,Columbia University | Kim Y.H.,Food Ingredients Center | Lu H.D.,Columbia University | And 3 more authors.
Biomacromolecules | Year: 2012

We have created a set of rationally designed peptides that form calcium-dependent hydrogels based on the beta roll peptide domain. In the absence of calcium, the beta roll domain is intrinsically disordered. Upon the addition of calcium, the peptide forms a beta helix secondary structure. We have designed two variations of our beta roll domain. First, we have mutated one face of the beta roll domain to contain leucine residues so that the calcium-dependent structural formation leads to dimerization through hydrophobic interactions. Second, an α-helical leucine zipper domain is appended to the engineered beta roll domain as an additional means of forming intermolecular cross-links. This full peptide construct forms a hydrogel only in calcium-rich environments. The resulting structural and mechanical properties of the supramolecular assemblies are compared with the wild-type domain using several biophysical techniques including circular dichroism, FRET, bis-ANS binding and microrheology. The calcium responsiveness and rheological properties of the leucine beta roll containing construct confirm the potential of this allosterically regulated scaffold to serve as a cross-linking domain for stimulus-responsive biomaterials development. © 2012 American Chemical Society.


Sathiyanarayanan G.,Konkuk University | Yi D.-H.,Konkuk University | Bhatia S.K.,Konkuk University | Kim J.-H.,Konkuk University | And 8 more authors.
RSC Advances | Year: 2015

A novel exopolysaccharide (EPS) producing psychrotrophic bacterium Flavobacterium sp. ASB 3-3 was isolated from Arctic glacier soil and identified. The optimum fermentation conditions for EPS production were an initial medium pH of 7.2 and an initial inoculum size of 5% (v/v). The maximum yield of EPS (7.25 ± 0.26 g L-1) was obtained after cultivation at 25 °C for 120 h with glycerol as the sole carbon source. The EPS was purified and its structural characteristics were analyzed by 1H and 13C NMR. The predominant repeating units of this EPS are (α, β) d-glucose and d-galactose and it is different from the structure of EPSs produced by other Arctic and Antarctic bacteria, which have mannose units. In addition, EPS has demonstrated a comparable emulsifying property than SDS and flocculating properties with kaolinite, suggesting their potential applications in various industries. The EPS also significantly improved the tolerance of Flavobacterium sp. and Escherichia coli from freeze-thaw cycles, suggesting that it might be used to survive in polar regions and it can have possible usage as microbial cryoprotectants. © The Royal Society of Chemistry 2015.


Yi D.-H.,Konkuk University | Sathiyanarayanan G.,Konkuk University | Seo H.M.,Konkuk University | Kim J.-H.,Konkuk University | And 6 more authors.
Bioprocess and Biosystems Engineering | Year: 2016

In this study, the environmental adaptive metabolic processes were investigated using a psychrotrophic polar bacterium Bacillus pumilus PAMC 23174 in response to various temperatures and nutrients, especially in regard to the synthesis of fatty acids. Fatty acid methyl ester analysis was performed using gas chromatography-mass spectrometry and we found that a sensitive changes in iso-branched fatty acid (iso-15:0) synthesis occurred when adjusting the nutritional ratio of branched chain fatty acids (anteiso/iso) with different temperatures, resulting in a change in the balance of anteiso- and iso-form fatty acids. We also observed that this Arctic bacterium preferred amino acid leucine for the synthesis of fatty acids. The increased and decreased synthesis of iso-form fatty acids in response to different temperatures and leucine preference, changes the fatty acid ratio in bacteria, which further affects the membrane fluidity and it is also directly correlated with survival of bacteria in an extreme environment. Hence, this study suggests that B. pumilus PAMC 23174 is a potential model organism for the analysis of the unique ecological adaptations of polar bacteria in changing and the extreme environments. © 2015 Springer-Verlag Berlin Heidelberg.


Sathiyanarayanan G.,Konkuk University | Bhatia S.K.,Konkuk University | Kim H.J.,Konkuk University | Kim J.-H.,Konkuk University | And 6 more authors.
RSC Advances | Year: 2016

An exopolysaccharide (EPS) was produced from psychrotrophic Arctic glacier fore-field soil bacterium Pseudomonas sp. PAMC 28620 using glycerol enriched medium and the maximum productivity 7.24 ± 0.31 g L-1 of EPS was obtained after 168 h of fermentation. The EPS was purified and analysed by HPLC, GC-MS, FT-IR, 1H and 13C NMR. The EPS obtained from Arctic strain PAMC 28620 exhibits a distinctive structural composition and the constituent sugar monomers are rhamnose, galactose, glucose, fucose, mannose and ribose. The purified EPS has shown excellent flocculating and emulsification capacities with promising biotechnological and ecological implications. From the metal removal experiments, the EPS exhibited remarkable metal adsorption (99%) potential adopting the order Fe2+ > Cu2+ > Mg2+ > Zn2+ > Mn2+ > Ca2+. FE-SEM combined with EDX analysis has shown that the metal ions were complexed or immobilized onto the EPS matrix and further reduced to nanoparticles (150-950 nm). This study is significant in terms of metal removal and reduction potential of Arctic bacterial EPS and the possible ecological roles of the EPS in Arctic environment. This journal is © The Royal Society of Chemistry 2016.


Bhatia S.K.,Konkuk University | Lee B.-R.,Konkuk University | Sathiyanarayanan G.,Konkuk University | Song H.-S.,Konkuk University | And 8 more authors.
Bioresource Technology | Year: 2016

In this study, a biosugar obtained from empty fruit bunch (EFB) of oil palm by hot water treatment and subsequent enzymatic saccharification was used for undecylprodigiosin production, using Streptomyces coelicolor. Furfural is a major inhibitor present in EFB hydrolysate (EFBH), having a minimum inhibitory concentration (MIC) of 1.9. mM, and it reduces utilization of glucose (27%), xylose (59%), inhibits mycelium formation, and affects antibiotic production. Interestingly, furfural was found to be a good activator of undecylprodigiosin production in S. coelicolor, which enhanced undecylprodigiosin production by up to 52%. Optimization by mixture analysis resulted in a synthetic medium containing glucose:furfural:ACN:DMSO (1%, 2. mM, 0.2% and 0.3%, respectively). Finally, S. coelicolor was cultured in a fermenter in minimal medium with EFBH as a carbon source and addition of the components described above. This yielded 4.2. μg/mg. dcw undecylprodigiosin, which was 3.2-fold higher compared to that in un-optimized medium. © 2016 Elsevier Ltd.


Seo H.-M.,Konkuk University | Jeon J.-M.,Konkuk University | Lee J.H.,Konkuk University | Song H.-S.,Konkuk University | And 8 more authors.
Journal of Industrial Microbiology and Biotechnology | Year: 2016

Furfural is a toxic by-product formulated from pretreatment processes of lignocellulosic biomass. In order to utilize the lignocellulosic biomass on isobutanol production, inhibitory effect of the furfural on isobutanol production was investigated and combinatorial application of two oxidoreductases, FucO and YqhD, was suggested as an alternative strategy. Furfural decreased cell growth and isobutanol production when only YqhD or FucO was employed as an isobutyraldehyde oxidoreductase. However, combinatorial overexpression of FucO and YqhD could overcome the inhibitory effect of furfural giving higher isobutanol production by 110 % compared with overexpression of YqhD. The combinatorial oxidoreductases increased furfural detoxification rate 2.1-fold and also accelerated glucose consumption 1.4-fold. When it compares to another known system increasing furfural tolerance, membrane-bound transhydrogenase (pntAB), the combinatorial aldehyde oxidoreductases were better on cell growth and production. Thus, to control oxidoreductases is important to produce isobutanol using furfural-containing biomass and the combinatorial overexpression of FucO and YqhD can be an alternative strategy. © 2015, Society for Industrial Microbiology and Biotechnology.


Jeon J.-M.,Konkuk University | Park H.,Hanyang University | Seo H.-M.,Konkuk University | Kim J.-H.,Konkuk University | And 7 more authors.
Bioprocess and Biosystems Engineering | Year: 2015

Shewanella oneidensis MR-1 is one of the most well-known metal-reducing bacteria and it has been extensively studied for microbial fuel cell and bioremediation aspects. In this study, we have examined S. oneidensis MR-1 as an isobutanol-producing host by assessing three key factors such as isobutanol synthetic genes, carbon sources, and electron supply systems. Heterologous Ehrlich pathway genes, kivD encoding ketoisovalerate decarboxylase and adh encoding alcohol dehydrogenase, were constructed in S. oneidensis MR-1. Among the composition of carbon sources examined, 2 % of N-acetylglucosamine, 1.5 % of pyruvate and 2 % of lactate were found to be the most optimal nutrients and resulted in 10.3 mg/L of isobutanol production with 48 h of microaerobic incubation. Finally, the effects of metal ions (electron acceptor) and direct electron transfer systems on isobutanol production were investigated, and Fe2+ ions increased the isobutanol production up to 35 %. Interestingly, deletion of mtrA and mtrB, genes responsible for membrane transport systems, did not have significant impact on isobutanol production. Finally, we applied engineered S. oneidensis to a bioelectrical reactor system to investigate the effect of a direct electron supply system on isobutanol production, and it resulted in an increased growth and isobutanol production (up to 19.3 mg/L). This report showed the feasibility of S. oneidensis MR-1 as a genetic host to produce valuable biochemicals and combine an electron-supplying system with biotechnological applications. © 2015 Springer-Verlag Berlin Heidelberg


Bhatia S.K.,Konkuk University | Kim Y.H.,Konkuk University | Kim H.J.,Konkuk University | Seo H.-M.,Konkuk University | And 6 more authors.
Bioprocess and Biosystems Engineering | Year: 2015

In this study, Escherichia coli cells overexpressing lysine decarboxylase (CadA) were used for cadaverine production. Barium alginate was selected as a matrix for immobilization of E. coli YH91. Free cells and immobilized cells (IC) were characterized for their physiochemical properties, and the optimum pH and temperature were determined as 6 and 37 °C, respectively. Immobilized cells were three times more thermally stable compared to free cells at the optimum temperature and had a half-life (t1/2) of 131 h. The free cells lost most of lysine decarboxylase activity after nine cycles, but in contrast immobilized cells retained 56 % of their residual activity even after the 18th cycle. The immobilized cells gave a maximum production of cadaverine (75.8 g/L) with 84 % conversion. © 2015 Springer-Verlag Berlin Heidelberg


PubMed | Food Ingredients Center, Soongsil University, Konkuk University and Korea Polar Research Institute
Type: Journal Article | Journal: Bioprocess and biosystems engineering | Year: 2016

In this study, the environmental adaptive metabolic processes were investigated using a psychrotrophic polar bacterium Bacillus pumilus PAMC 23174 in response to various temperatures and nutrients, especially in regard to the synthesis of fatty acids. Fatty acid methyl ester analysis was performed using gas chromatography-mass spectrometry and we found that a sensitive changes in iso-branched fatty acid (iso-15:0) synthesis occurred when adjusting the nutritional ratio of branched chain fatty acids (anteiso/iso) with different temperatures, resulting in a change in the balance of anteiso- and iso-form fatty acids. We also observed that this Arctic bacterium preferred amino acid leucine for the synthesis of fatty acids. The increased and decreased synthesis of iso-form fatty acids in response to different temperatures and leucine preference, changes the fatty acid ratio in bacteria, which further affects the membrane fluidity and it is also directly correlated with survival of bacteria in an extreme environment. Hence, this study suggests that B. pumilus PAMC 23174 is a potential model organism for the analysis of the unique ecological adaptations of polar bacteria in changing and the extreme environments.

Loading Food Ingredients Center collaborators
Loading Food Ingredients Center collaborators