• Proceedings of the Korean Environmental Sciences Society Conference
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• 2008.11a
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• pp.282-285
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• 2008

At least 15% of the C polykrikoides cells that precipitated to the bottom layer either by the addition of loess or no addition survived for 1 week at all growth phases, rather than disappearing immediately after precipitating. However, no live cells were observed after 20 days, regardless of phase or loess addition. In the exponential phase, the number of C polykrikoides cells increased to >2886 cells/ml after loess was added. However, in the stationary phase, the number of cells did not increase until 18 days. In the exponential phase, those C polykrikoides that survived precipitation caused by scattering loess on cultures did not appear to have the ability to cause red tides again because of the short red tide periods in the field, long lag time after loess addition, and low survival rate after loess addition.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2877-2883
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• 2010

The folding kinetics of $WT^*$ ubiquitin variant with valine to alanine mutation at sequence position 26 (HubWA) was studied by stopped-flow fluorescence spectroscopy. While unfolding kinetics showed a single exponential phase, refolding reaction showed three exponential phases. The semi-logarithmic plot of urea concentration vs. rate constant for the first phase showed v-shape pattern while the second phase showed v-shape with roll-over effect at low urea concentration. The rate constant and the amplitude of the third phase were constant throughout the urea concentrations, suggesting that this phase represents parallel process due to the configurational isomerization. Interestingly, the first and second phases appeared to be coupled since the amplitude of the second phase increased at the expense of the amplitude of the first phase in increasing urea concentrations. This observation together with the roll-over effect in the second folding phase indicates the presence of intermediate state during the folding reaction of HubWA. Quantitative analysis of Hub-WA folding kinetics indicated that this intermediate state is on the folding pathway. Folding kinetics measurement of a mutant HubWA with hydrophobic core residue mutation, Val to Ala at residue position 17, suggested that the intermediate state has significant amount of native interactions, supporting the interpretation that the intermediate is on the folding pathway. It is considered that HubWA is a useful model protein to study the contribution of residues to protein folding process using folding kinetics measurements in conjunction with protein engineering.

• Journal of Microbiology
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• v.34 no.2
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• pp.172-178
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• 1996

Methylobacillus sp. strain SK1, which grows only on methanol, was found to grow in the absence of added copper. The doubling time (t$_{d}$ = 1.3 h) of the bacterium growing at the exponential growth phase at 30.deg.C in the absence of copper was the same as that of the cell growing in the presence of copper. The bacterium growing after the exponential phase in the absence of copper, however, grew faster than the cell growing in the presence of copper. Cells harvested after thee arly stationary phase in the presence of copper were found to exhibit no methanol dehydrogenase (MDH) activity, but the amount and subunit structure of the enzyme in the cells were almost the same as that in cells harboring active MDH. Pellets of the cells harvested after the early stationary phase in the presence of copper were pale green. Cell-free extracts prepared from cells harvested at the early stationary phase in the presence of copper were pink and exhibited MDH activity, but it turned dark-green rapidly from the surface under air. The green-colored portions of the extracts showed no MDH activity and contained c-type cytochromes that were oxidized completely. The inactive MDH activity and contained c-type cytochromes that were oxidized completely. The inactive MDH proteins in the green portions were found to have antigenic sites identical to those of the active one as the inactive MDHs in cells grown in the presence of copper. The bacterium was found to accumulate copper actively during the exponential growth phase. MDH prepared from cells grown in the presence or absence of copper was found to be more stable under nitrogen gas than under air. Methanol at 10 mM was found to enhance the stability of the MDH under air.r.

• Biotechnology and Bioprocess Engineering:BBE
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• v.3 no.1
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• pp.11-14
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• 1998

A toluene-oxidizing strain of Pseudomanas mendocina KR1 containing toluene-4-mono-oxygenase (TMO) completely degrades TCE with the addition of toluene as a co-substrate in aerobic condition. In order to construct in situ bioremediation system for TCE degradation without any growth-stimulating nutrients or toxic inducer such as toluene, we used the carbon-starvation promoter of Pseudomonas putida MK1 (Kim, Y. et al., J. bacteriol., 1995). Upon entry into the stationary phase due to the deprivation of nutrients, this promoter is strongly induced without further cell growth. The TMO gene cluster (4.5 kb) was spliced downstream of the carbon starvation promoter of Pseudomonas putida MK1, already cloned in pUC19. TMO under the carbon starvation promoter was not expressed in E. coli cells either in stationary phase or exponential phase. For TMO expression in Pseudomonas strains, tmo and carbon starvation promoter region were recloned into a modified broad-host range vector pMMB67HES which was made from pMMB67HE(8.9 kb) by deletion of tac promoter and lacIq (about 1.5 kb). Indigo was produced by TMO under the carbon starvation promoter in a Pseudomonas strain of post-exponential phase on M9 (0.2% glucose and 1mM indole) or LB. 18% of TCE was degraded in 14 hours after entering the stationary phase at the initial concentration of 6.6 ${\mu}$M in liquid phase.

• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.918-925
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• 2008

Controlling the light energy and major nutrients is important for high cell density culture of cyanobacterial cells. The growth phase of Anabaena variabilis can be divided into an exponential growth phase and a deceleration phase. In this study, the cell growth in the deceleration phase showed a linear growth pattern. Both the period of the exponential growth phase and the average cell growth rate in the deceleration phase increased by controlling the light intensity. To control the light intensity, the specific irradiation rate was maintained above $10\;{\mu}mol/s/g$ dry cell by increasing the incident light intensity stepwise. The final cell density increased by controlling the nutrient supply. For the control of the nutrient supply, nitrate, phosphate, and sulfate were intermittently added based on the growth yield, along with the combined control of light intensity and nutrient concentration. Under these control conditions, both final cell concentration and cell productivity increased, to 8.2 g/l and 1.9 g/l/day, respectively.

• Proceedings of the IEEK Conference
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• 2001.06c
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• pp.51-54
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• 2001

Recently Hwang and Li［1］ proposed a remote user authentication scheme using smart cards. Their scheme is based on the ElGamal public key cryptosystem and does not need to maintain a password table for verifying the legitimacy of the login users. In this paper, we proposed an advanced user authentication scheme using smart cards. Unlike Hwang and Li's scheme, smart card contains a pair of public parameters(h, P) where h is a hash function which is used in login phase. In result, we reduce one exponential computation frequency in login phase and two exponential computation frequencies in authentication phase with comparing the Hwang and Li's scheme. The proposed scheme not only provides the advantages as security of Hwang and Li's scheme, but also reduces computation cost.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.1856-1861
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• 2006

A Bacillus sp. A-6 strain that produced xylanase was isolated from rice bran. The optimal temperature and pH for xylanase activity of the culture supernatant of Bacillus sp. A-6 were 40$^{\circ}C$ and pH 7, respectively. The optimal temperature and pH for xylanase production in the xylan medium were 30$^{\circ}C$ and pH 9, respectively. The optimal concentrations of oat spelt xylan and peptone for xylanase production were 0.5% and 1.5%, respectively. The best nitrogen sources for xylanase production was beef extract, but xylanase production was also supported comparably by tryptone and peptone. The bacterial growth in the optimal xylan medium reached stationary growth phase after 12 h of incubation. The xylanase production in the culture supernatant increased dramatically during the initial 12 h exponential growth phase and then remained constant at 23.8-24.5 unit/ml during the stationary growth phase. The pH of the culture medium decreased from 8.8 to 6.7 during the exponential growth phase and subsequently increased to 8.1 during the stationary growth phase. Rice bran, sorghum bran, and wheat bran as well as oat spelt xylan induced xylanase production. The xylanase production was repressed when glucose was added to the xylan-containing medium.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.2
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• pp.137-143
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• 2008

Rapid canopy closure (RCC) is one of the physiological attributes that may enhance genetic yield potential of rice (Oryza sativa L.) in a growing season. Crop growth before canopy closure could be described by an exponential equation of $y\;=\;{\alpha}{\cdot}{\exp}({\beta}{\cdot}t)$ where $\alpha$ is the crop leaf area index (LAI) or shoot dry weight (DW), t is the thermal time, $\beta$ is the LAI or DW at the beginning of the exponential growth and is the relative growth rate of LAI ($m^2m^{-2}^{\circ}C^{-1}$) or DW($gg^{-2}^{\circ}C^{-1}$). Field experiment using 22 cultivars revealed that the exponential growth phase before canopy closure can be divided into two sections; an earlier section during which crop dry weight and LAI of varieties are highly dependent on $\alpha$ and a second section where crop dry weight and LAI are highly dependent on $\beta$. Grain weight had significantly positive correlation with $\alpha$ parameter and dry weight and LAI during early exponential phase. The parameter $\beta$ of the exponential growth curve had positive and significant correlation with the LAI and dry weight during the late exponential growth phase, grain number per unit area, and grain yield. There was genotypic difference for RCC parameters, $\alpha$ and $\beta$, indicating the possibility of genetic improvement for these traits.

• Journal of Food Hygiene and Safety
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• v.12 no.3
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• pp.181-187
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• 1997

Lactobacillus acidophilus NCFM, Lactobacillus casei YIT 9018, Bifidobacterium longum 8001, and Bifidobacterium longum 8025 at the level of 106 cfu/$m\ell$ were cultured with 104 cfu/$m\ell$ of Escherichia coli O157:H7 KSC 109 or Salmonella typhimurium ATCC14028, in order to verify the effects of lactic acid bacteria and bifidobacteria on the growth of the pathogens. In the mixed culture of lactic acid bacteria with E. coli O157:H7 KSC 109, Growth inhibition and atypical microcolonies of E. coli O157:H7 KSC 109 were observed. The pathogens inoculated grew for 5 hors (pH 5.3), by the time L. acidophilus NCFM reached the exponential growth phase, and then the surviving pathogens were decreased to 101 cfu/$m\ell$ after 35 hours. When L. caseiYIT 9018 was grown with the pathogens, they grew for 10 hours (pH 4.6), by the time L. casei YIT 9018 reached the end of exponential growth phase, and then the surviving pathogens were decreased drastically. Up to the stationary growth phase of lactic acid bacteria, L. acidophilus NCFM exhibited stronger inhibition against the pathogens than L. casei YIT 9018 did, which might be attributed to its faster growth. Likewise bifidobacteria inhibited the growth of the pathogens tested, bifidobaceria was weaker in the inhibitory activity than lactic acid bacteria. When Bifidobacterium longum 8001 was cultured with the pathogens, E. coli O157:H7 KSC 109 was gradually ingibited at the stationary growth phase of bifidobacteria, atypical microcolonies were formed on Levine EMB medium after 48 hours, and Salmonella grew up to 106 dfu/$m\ell$, then was drastically ingibited at the exponential growth phage of Bifidobacterium longum 8001. But when Bifidobacteriuam longum 8025 was cultured with the pathogens, the pathogens grew to the same level of Bifidobacteriuam longum 8025 was cultured with the pathogens, the pathogens grew to the same lever of Bifidobacteriuam longum 8025 after 10 hours, then the surviving pathogens were decreased drastically.

• KSBB Journal
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• v.9 no.2
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• pp.200-210
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• 1994

In batch bioreactor fermentations for cyclosporin A (CyA) production, good potential for bioprocess improvement was demonstrated in the immobilized cell system, providing appreciably better utilization of the catalytic activity of the biomass than the freely suspended cells, especially during the exponential phase. When concentrated nutrient medium was added pulsely during the exponential phase of cell growth(at hour 139 of fermentation), reactivation and regermination in both immobilized and suspended cell cultures were observed to contribute to the longevity of CyA production, maintaining maximum CyA titre until 250 hours of fermentation. Contrarily, simple batch fermentations without any supplement of medium in both systems showed repid decrease in CyA concentrations during the late stationary phase. Notably, the CyA yield coefficient $(Y_p/x)$ for the immobilized cell system was maintained quite high even after the pulse addition of the concentrated full medium, reaching almost 80% of the level attained during the exponential phase. This is in sharp contrast when compared with the corresponding value of 58% in the case of parallel-suspended cells. This pattern of CyA production resulted in considerably enhanced CyA production in the immobilized cell system, reaching almost 2 time higher maximum CyA production in comparison with the free cell system.