• KSBB Journal
• /
• v.21 no.6 s.101
• /
• pp.461-465
• /
• 2006

We investigated the protein productivity of the promoters for genes showing prolonged induction upon cold shock in Escherichia coli. Six low temperature inducible genes (frdA, glpB, hypB, katG, nupG, ompT) were selected based on the previously reported cDNA microarray based global transcription profiling of Escherichia coli Kl2 in response to cold shock. Their promoter regions were isolated from the genomic DNA of E. coli JM109 and expression levels induced by the promoters were examined by using green fluorescence protein (GFP) as a reporter at $15^{\circ}C$ and $37^{\circ}C$. Among the six promoters, the promoter for nupG showed the highest and prolonged expression at both temperatures and the cold inducibility of nupG promoter was not observed.

• 한국생물공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.644-648
• /
• 2005

Dextranase (${\alpha}$-1,6-D-glucan-6-glucanogydrolase:E.C. 3.2.1.11) catalyzes the hydrolysis of ${\alpha}$-(1.6) linkages of dextran. A lsd1 gene encoding an extracellular dextranase was isolated from the genomic DNA of L. starkeyi. The lsd11 gene is a synthetic dextranase (lsd1) after codon optimization for gene expression with Pichia pastoris system. A open reading frame of lsd11 gene was 1827 bp and it was inserted into the pPIC3.5K expression vector. The plasmid linearized by Sac I was integrated into the 5'AOX region of the chromosomal DNA of P. pastoris. The lsd11 gene fragment encoding a mature protein of 608 amino acids with a predicted molecular weight of 70 kDa, was expressed in the methylotrophic yeast P. pastoris by controling the alcohol oxidase-1 (AOX1) promoter. The recombinant lds11 was optimized by using the shake-flask expression and upscaled using fermentation technology. More than 9.8 mg/L of active dextranase was obtained after induction by methanol. The optimum pH of LSD11 was found to be 5.5 and the optimum temperature $28^{\circ}C$.

• Food Science and Biotechnology
• /
• v.15 no.6
• /
• pp.942-947
• /
• 2006

The effect of oat bran extracts on the formation of aberrant crypt foci (ACF) in the colon induced by 1,2-dimethylhydrazine (DMH) was studied in F344 male rats. Extracts were prepared using various combinations of temperature (40, 45, 50, 55, or 60$^{\circ}C:\;X_1$), ethanol concentration (0,5, 10, 15, or 20%: $X_2$), and pH (5, 6, 7, 8, or 9: $X_3$). Among the various extracts tested, one ethanol extract (EE; $45^{\circ}C$, 15% ethanol at pH 6) and one water extract (WE; $50^{\circ}C$ at pH 5) were selected based on their in vitro antitumor activity. The animals were fed with basal diet alone or basal diet supplemented with 0.25 or 0.5% of EE or WE for 6 weeks. During the initial 2 weeks of the 6-week test period, the rats were subcutaneously injected with DMH (30 mg/kg) 4 times for the induction of ACF. DMH induced an average of 322.7 and 142.9 aberrant crypts (AC) and ACF, respectively. A low dose (0.25%) of EE (containing 38.3% ${\beta}$-glucan) and WE (containing 22.8% ${\beta}$-glucan) greatly reduced the numbers of DMH-induced AC and ACF. Significantly, ACF consisting of more than 3 AC were reduced by half in which the effect of EE, containing a higher concentration of ${\beta}$-glucan, was superior to that of WE. These results demonstrate that oat bran extracts may confer protection against colon carcinogenesis.

• Journal of the Korean Society for Heat Treatment
• /
• v.28 no.5
• /
• pp.239-249
• /
• 2015

Various amount of NbC carbide was intentionally formed in a matrix-type cold-work tool steel by controlled amount of Nb and C addition. And the effect of NbC addition on the mechanical properties was investigated. Four alloys with different Nb and C contents were cast by vacuum induction melting, then hot forging and spheroidizing annealing were conducted. The machinability of the annealed specimens was examined with 3 different cutting tools. And tensile tests at room temperature were conducted. After quenching and tempering, hardness and impact toughness were measured, while wear resistance was evaluated by disk-on-plate type wear test. The increasing amount of NbC addition resulted in degraded machinability with increased strength, whereas the absence of NbC also led to poor machinability due to high toughness. After quenching and tempering, the additional NbC improved wear resistance with increasing hardness, whereas it deteriorated impact toughness. Therefore, it could be found that a moderate addition of NbC was desirable for the balanced combination of mechanical properties.

• Transactions of Materials Processing
• /
• v.6 no.3
• /
• pp.239-249
• /
• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for filling phenomena in forging process of arbitrarily shaped dies. To produce a automotive part which has good mechanical property, the filling pattern according to die velocity and solid fraction distribution has to be estimated for arbitrarily shaped dies. Therefore, the estimation of filling characteristic in the forging simulation with arbitrarily shaped dies of semi-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for arbitrarily shaped dies is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process with arbitrarily shaped dies is performed to the isothermal conditions of two dimensional problems. To analysis of forging process by using semi-solid materials, a new stress-strain relationship is described, and forging analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for forging force and filling limitations will be compared to experimental data. The filling simulation of simple products performed with the uniform billet temperature(584$^{\circ}C$) from the induction heating by the commercial package MAGMAsoft. The initial step of computation is the touching of semi-solid material with the end of die gate and the initial concept of proposed system just fit with the capability of MAGMAsoft.

• Journal of Food Hygiene and Safety
• /
• v.3 no.1
• /
• pp.19-26
• /
• 1988

Most of meat spoilage bacteria area Gram negative, which are very sensitive to freezing ; for instance , 90% of E. coli cells are killed or sub-lethally injured by freezing at -3$0^{\circ}C$, and the freeze-injury rate is dependent upon freezing rate. Since the injured bacterial cells are sensitive to selective agents, they fail to multiply in selective media. Injured bacterial cells are, however, capable of spontaneous repair at appropriate environmental and nutritional conditions . Enumeration of injured bacterial cells involves artificial induction of repair at these conditions. Cubic beef samples(3$\times$3$\times$3cm) were frozen at -6$0^{\circ}C$, -4$0^{\circ}C$, or -18$^{\circ}C$. The samples frozen at each temperature were thawed at 4$^{\circ}C$, 2$0^{\circ}C$, or by microwave . After these respective freezing an thawing treatments, the percentage of sub-lethally injured total coliforms out of total surviving ones was measured and compared. The results were as follows: 1. The interaction between freezing and thawing on injury rate was not significant. 2. The injury rates(as means of all three thawing treatments post-freezing) by freezing at -6$0^{\circ}C$, -4$0^{\circ}C$, or -18$^{\circ}C$ were 32.2$^{\circ}C$ and 19.2$^{\circ}C$ respectively . 3. The injury rates(as means of all three freezing treatments)by thawing at 4$^{\circ}C$, 2$0^{\circ}C$, or by microwave were 49.3%, 11.7% and 21.0% respectively. The highest injury rate was caused by freezing at -6$0^{\circ}C$ and subsequent thawing at 4$^{\circ}C$. However since the injury rates by freezing treatment were not significantly different, freezing at -18$^{\circ}C$ and subsequent thawing at 4$^{\circ}C$ can also be recommended , from an economic perspective.

• ALGAE
• /
• v.35 no.2
• /
• pp.123-131
• /
• 2020

Sargassum macrocarpum is a rich source of anti-inflammatory compounds. Recently, one of the compounds, tuberatolide B, has been reported as a functional anti-inflammatory additive for foods and nutraceuticals. The artificial seeding, growth and maturation of S. macrocarpum were investigated from May 2018 to September 2019. Indoor culture experiments for induction of egg release were conducted at temperatures of 17, 20, 23, and 26℃ and irradiances of 0, 10, 20, 40, and 80 μmol photons m^-2 s^-1 under 14 : 10 h (L : D) photoperiod. Within a given treatment combination, higher temperatures and irradiance levels favoured the maturation of receptacles in S. macrocarpum. Using artificial temperature and irradiance control, thalli matured one month earlier than thalli in nature. Under natural condition, receptacle formation began in April, and the eggs were released in June and July. The release of eggs from the receptacles was promoted at 17-20℃ and 40-80 μmol photons m^-2 s^-1, and the fastest growth of germlings occuring at 15-17℃ and 40 μmol photons m^-2 s^-1. For mature thalli, 300 g wet-weight was sufficient to seed 100 m of seed string. Thalli grew to 10.5 ± 2.6 cm in length at a density of 6.7 ± 3.3 individuals m^-1 after 1 year of cultivation, from germination. This study demonstrates that it is possible to cultivate S. macrocarpum for the production of anti-inflammatory products.

• The Korean Journal of Mycology
• /
• v.14 no.4
• /
• pp.273-280
• /
• 1986

The degree of autolysis and lytic enzyme production in the culture filtrate of Rhizopus oryzae was investigated. The formation of protoplast by using autolytic enzymes from Rh. oryzae was also attempted. Protoplasts were liberated from Rh. oryzae mycelium by lytic enzymes present in autolytic-phase culture filtrate. Maximum release of chitosanase and proteolytic enzyme into culture filtrate during autolysis was corresponded to maximum protoplast-liberating activity. High yields of protoplasts were obtained from 10 hr-age of Rh. oryzae mycelium with 0.5 M mannitol as osmotic stabilizer. The optimum temperature and pH for mycelium digestion were $25{\sim}30^{\circ}C$ and $6.0{\sim}6.5$ respectively. The mycelium of the 18 hours cultures were treated with autolytic enzyme in same volume of osmotic stabilizer at $30^{\circ}C$ for 5 hours and then it was confirmed by scanning electoron microscope that protoplast were produced beside the digesting cell wall of the fungi.

• The Korean Journal of Mycology
• /
• v.14 no.3
• /
• pp.189-194
• /
• 1986

The aim of this study was to investigate physiological chracteristics of Lentinus edodes in Korea. We tried to detect properties of the several wood-degradative enzymes and investigate patterns of the enzyme production. A specific carbon source was used in the enzyme induction media for each enzymes, and the crude extract was used for the enzyme solution. With these enzyme solution, we investigated optimum temperature and pH conditions of their reactions. Moreover we investigated transition patterns of the enzyme production of the several wood-degrad­ative enzmes from Complex and Saw dust media for the purpose of studying the mechanisms of the wood component degradation by this fungus. It was assumed that the order of the wood com­ponent degradation was cellulose, xylan, and then pectic substances, and that the synergistic effects of these substances also influenced the degradation of wood components.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.11
• /
• pp.1529-1533
• /
• 2010

The inulinase gene (INU1) from Kluyveromyces marxianus NCYC2887 was overexpressed by using the GAL10 promotor in a ${\Delta}ga180$ strain of Saccharomyces cerevisiae. The inulinase gene lacking the original signal sequence was fused in-frame to a mating factor ${\alpha}$ signal sequence for secretory expression. Use of the ${\Delta}ga180$ strain allowed for the galactose-free induction of inulinase expression using a glucose-only medium. Shake-flask cultivation in YPD medium produced 34.6 U/ml of the recombinant inulinase, which was approximately 13-fold higher than that produced by K. marxianus NCYC2887. It was found that the use of the ${\Delta}ga180$ strain improved the expression of inulinase in the recombinant S. cerevisiae in both aerobic and anaerobic conditions by about 2.9- and 1.7-fold, respectively. A 5-l fed-batch fermentation using YPD medium was performed under aerobic condition with glucose feeding, which resulted in the inulinase production of 31.7 U/ml at the $OD_{600}$ of 67. Ethanol fermentation of dried powder of Jerusalem artichoke, an inulin-rich biomass, was also performed using the recombinant S. cerevisiae expressing INU1 and K. marxianus NCYC2887. Fermentation in a 5-l scale fermentor was carried out at an aeration rate of 0.2 vvm, an agitation rate of 300 rpm, and with the pH controlled at 5.0. The temperature was maintained at $30^{\circ}C$ and $37^{\circ}C$, respectively, for the recombinant S. cerevisiae and K. marxianus. The maximum productivities of ethanol were 59.0 and 53.5 g/l, respectively.