• Microbiology and Biotechnology Letters
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• v.14 no.2
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• pp.193-198
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• 1986

Improvement of productivity in ethanol fermentation was attempted using a hollow fiber bioreactor (HFR) where Saccharomyces cerevisiac var. ellipsoideus cells were recycled to achieve a high yeast concentration. Industrial wort was used as the fermentation media without supplying any additional nutrients. The performances in hollow fiber recycle reactor (HFR) were compared with those of batch and continuous cultures. In a continuous culture with 11$^{\circ}$P and 15$^{\circ}$P wort media final ethanol concentrations were 4.71% and 5.82% (v/v) and yields 86.2% and 78.6% respectively when the dilution rate (D) was 0.1 h$^{-1}$, in contrast, the ethanol concentration and productivity in HFR were 7.64%(v/v) and 6.1g/l/h at D=0.1h$^{-1}$ with 15$^{\circ}$P media. When the dilution rate was increased to 0.2 h$^{-1}$, the concentration and the Productivity were 7.62% (v/v) and 12.2g/l/h. At D=0.3h$^{-1}$ the sugar was completely consumed and the productivity was 18.1g/l/h. This correponds to 4 times that in continuous system and 16.3 times that in the batch system performed in comparable conditions.

• Microbiology and Biotechnology Letters
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• v.43 no.2
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• pp.134-141
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• 2015

An agarolytic marine bacterium (H9) was isolated from the coastal seawater of the West Sea, South Korea. The isolate, H9, was gram-negative and rod-shaped with a smooth surface and polar flagellum. Cells grew at 20-30℃, between pH 5.0 and 9.0, and in ASW-YP (Artificial Sea Water-Yeast extract, Peptone) media containing 1-5% (w/v) NaCl. The G+C content was 41.56 mol%. The predominant isoprenoid quinone in strain H9 was ubiquinone-8. The major fatty acids (>10%) were C_16:1ω7c (34.3%), C_16:0 (23.72%), and C_18:1ω7c (13.64%). Based on 16S rRNA gene sequencing, and biochemical and chemotaxonomic characterization, the strain was designated as Pseudoalteromonas sp. H9 (=KCTC23887). In liquid culture supplemented with 0.2% agar, the cell density and agarase activity reached a maximum level of OD = 4.32 (48 h) and OD = 3.87 (24 h), respectively. The optimum pH and temperature for the extracellular crude agarases of H9 were 7.0 and 40℃, respectively. Thin-layer chromatography analysis of the agarase hydrolysis products revealed that the crude agarases hydrolyze agarose into neoagarotetraose and neoagarohexaose. Therefore, the new agar-degrading strain, H9, can be applicable for the production of valuable neoagarooligosaccharides and for the complete degradation of agar in bio-industries.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.98-103
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• 2012

For screening of useful enzymes producing microorganisms from Meju, we isolated high lipase producing strains and their lipolytic enzyme activities were then tested. The lipolytic enzyme activities of isolated microorganisms were therefore tested on the Y124 strain. The gene sequence analysis of ITS from Y124 strain revealed Yarrowia lipolytica. Lipase production by the Y124 strain was studied in media containing various carbon sources. The Y124 strain drastically increased lipolytic enzyme activity in YPO media containing olive oil, as well as in YPDO media containing both olive oil and glucose. Maximal lipase production was achieved in YPD (yeast extract-peptone-D-glucose) media containing 0.7% olive oil when cultured at $30^{\circ}C$ for 8 hrs. The lipase produced from the Y124 strain showed the highest activity in p-NPO (p-nitrophenyl octanoate ($C_8$)), amongst the various p-nitrophenyl esters.

• Journal of Animal Science and Technology
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• v.48 no.4
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• pp.603-610
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• 2006

This study was conducted to investigate the feeding effect of selenium provided by different sources on the physico-chemical properties of M. longissimus thoracis. Twenty Hanwoo steers(20～24 months, approximately 613kg) were assigned to 4 different feeding groups of each five, depending on the sources of selenium such as inorganic selenium(sodium selenite), organic selenium(Yeast, USA Sel-Plex), Se-SMC(Se-spent mushroom compost) and the control(no selenium). The selenium level in feed was 0.9 ppm for all groups except the control. Animals were fed with different feeding treatments for 12 weeks and slaughtered at National Livestock Research Institute. The inorganic selenium group had the highest cooking loss(CL. %) and followed by the Se-SMC group and organic selenium group. No significant differences in chemical composition, WB-shear forces, water-holding capacity(WHC) and sensory properties were found among the groups(P>0.05). There were 40% frequencies of grade A in the inorganic selenium group and followed by the organic selenium group(20%). Se-SMC group had 80% of frequencies for grade 1+ and followed by the inorganic selenium group(40%), whereas the organic selenium group and the control group had the 20% frequencies for grade 1+. From the results of this study showed that the selenium sources did not affect chemical composition, WHC and tenderness of Hanwoo steers. However, the inorganic selenium group had the highest cooking loss(%) and lowest pH when compared to the other groups.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.999-1006
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• 2015

The endo-polygalacturonase gene (endo-pgaA) was cloned from DNA of Aspergillus niger SC323 using the cDNA synthesized by overlapping PCR, and successfully expressed in Saccharomyces cerevisiae EBY100 through fusing the α-factor signal peptide of yeast. The fulllength cDNA consists of 1,113 bp and encodes a protein of 370 amino acids with a calculated molecular mass of 38.8 kDa. After induction by galactose for 48 h, the activity of recombinant endo-PgaA in the culture supernatant can reach up to 1,448.48 U/mg. The recombinant protein was purified to homogeneity by ammonium sulfate precipitation and gel filtration column chromatography and subsequently characterized. The optimal pH and temperature of the purified recombinant enzyme were 5.0 and 50℃, respectively. The Michaelis-Menten constant (K_m) and maximal velocity (V_max) of the enzyme for pectin were 88.54 μmol/ml and 175.44 μmol/mg/min, respectively. The enzyme activity was enhanced by Ca²⁺, Cu²⁺, and Na⁺, and strongly inhibited by Pb²⁺ and Mn²⁺. The pectin hydrolysates were mainly galacturonic acid and other oligo-galacturonates. Therefore, these characteristics suggest that the recombinant endo-PgaA may be of potential use in the food and feed industries.

• Microbiology and Biotechnology Letters
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• v.40 no.4
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• pp.348-355
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• 2012

In the present study, we investigated the overexpression and characterization of bovine pancreatic (bp)- DNase I in Saccharomyces cerevisiae and Pichia pastoris. The bp-DNase I gene was fused in frame with the GAL10 promoter, $MF{\alpha}$, and GAL7 terminator sequences, resulting in the plasmid, pGAL-$MF{\alpha}$-DNaseI (6.4 kb). Also, the bp-DNase I gene was fused in frame with the AOX1 promoter, $MF{\alpha}$, and AOX1 terminator sequences, resulting in the plasmid, pPEXI (8.8 kb). The recombinant plasmids, pGAL-$MF{\alpha}$-DNaseI and pPEXI were introduced into S. cerevisiae and P. pastoris host cells, respectively. When the transformed yeast cells were cultured at $30^{\circ}C$ for 48 h in galactose or methanol medium, bp-DNase I was overexpressed and the most of activity was found in the extracellular fraction. P. pastoris transformant activity showed 45.5 unit/mL in the culture medium at 48 h cultivation, whereas S. cerevisiae transformant revealed 37.7 unit/mL in the extracellular fraction at 48 h cultivation. The enzymatic characteristics, such as DNA cleavage and half life were investigated. Treatment of the recombinant DNase I from P. pastoris induced degradation of the calf thymus DNA within 1 minute, and this DNA degradation rate was higher than that of commercial bp-DNase I (SIGMA) and the recombinant DNase I from S. cerevisiae.

• The Journal of Natural Sciences
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• v.16 no.1
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• pp.15-29
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• 2005

To produce a thermostable cyclodextrin by using thermotolerant cyclomaltodextrin glucanotransferase(CGTase), a thermophilic and alkalophilic bacterium isolate, designated B-13 showing the highest CGTase activity was isalated from natural sources and identified as Bacillus cereus B-13 based on the morphological and physiological characteristics, and 16S rRNA sequence. The maximal CGTase activity (130 U/ml) was obtained when Bacillus cereus B-13 was cultured in SYC medium containing 2.0% soluble starch, 1.0% yeast extracts, 1% corn steep liquor and 1% $Na_2CO_3$ (pH 8.5) at $50^{\circ}C$ for 24 h and about 80% of maximal activity was also showed in he culture broth of $60^{\circ}C$ for 18 h. Optimum reaction temperature and pH of the partial purified CGTase for soluble starch were $65^{\circ}C$ and pH 8.5-9.0 respectively. The partial purified CGTase were also stable below $80^{\circ}C$ and pH 5.0-10.0. When 1% soluble starch was digested with the partial purified CGTase, the yield of cyclodextrin was 49%.

• Korean Journal of Plant Tissue Culture
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• v.26 no.1
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• pp.41-47
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• 1999

Phenylalanine ammonia-lyase (PAL; EC 4, 3, 1, 5) genomic clones were isolated from tomato(Lycopersicon esculentum L.) genomic DNA libraries using tomato PAL5 cDNA sequences as probes. The nucleotide sequences of tPAL1, tPAL4 and tPAL5 were compared. tPAL5 contains an open reading frame encoding a polypeptide of 722 amino acids, interrupted by a 710 bp intron in the codon for the amino acid 139. tPAL1 encodes a polypeptide of 249 amino acids which is much shorter than tPAL5 gene due to a premature stop codon and does not contain an intron. tPAL4 encodes a polypeptide of 357 amino acids, interrupted by a 305 bp intron in the codon for the amino acid 138. Premature stop codons observed in tPAL1 and tPAL4 gene produce a short polypeptide rather than a normal polypeptide (722 aa). tPALl shows 87.2% homology with tPAL4 and 85.3% homology with tPAL5 gene whereas tPAL4 showes 91.4% homology with tPAL5 at nucleotide level. In general, phylogenetic analysis showed that genes isolated from tomato, potato, and sweet potato were belong to the same group and another dicot plants such as parsley, bean, soybean, pea and alfalfa formed another group. PAL genes isolated from rice and yeast showed very low homology with other PAL genes and formed the other group.

• Journal of Life Science
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• v.27 no.3
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• pp.339-345
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• 2017

Carotenoids are natural lipid-soluble pigments, which are produced primarily by bacteria, algae, and plants. Many studies have focused on the identification, production, and utilization of natural sources of astaxanthin from algae, yeast, and crustacean byproducts as an alternative to the synthetic pigment, which is mostly used today. The aim of the present study was to identify a mutant of Paracoccus haeundaensis by exposure to UV and ethyl methanesulfonate (EMS). The mutant was then exposed to nutrient stress conditions to isolate an astaxanthin-hyperproducing strain, followed by characterization of the mutant. The survival rate decreased in accordance with an increase in the UV exposure time and an increase in the EMS concentration. A mutant of the original P. haeundaensis strain was identified that showed hyperproduction of astaxanthin following exposure to UV irradiation (20 min) and EMS treatment (0.4 M concentration). The optimal culture conditions for the PUE mutant were $25^{\circ}C$, pH 7-8, and 3% NaCl. The effects of various carbon and nitrogen sources on the growth and astaxanthin production of PUE were examined. The addition of 1% raffinose and 3% potassium nitrate influenced cell growth and astaxanthin production. The selected mutant exhibited an increase of 1.58 folds in astaxanthin content compared to initial wild type strain. A genetically stable mutant strain obtained using mutagen (UV irradiation and EMS treatment) may be a suitable candidate for further industrial scale production of astaxanthin.

• Korean Journal of Plant Tissue Culture
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• v.25 no.6
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• pp.453-475
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• 1998

During the 100 years since the initial discovery of meiotic phenomenon many brilliant aspects have been elucidated, but further researches based on light microscopy alone as an experimental tool have been found to have some limits and shortcomings. By the use of electron microscopy and armed with the advanced knowledges on modern genetics and biochemistry it has been possible to applu molecular technology in gaining information on the detailed aspects of meiosis. As synapsis takes place, a three-layered proteinous structure called the synatonemal complex starts to form in the space between the homologous chromosomes. To be more precise, it begins to form along the paired chromosomes early in the prophase I of meiotic division. The mechanism that leads to precise point-by-point pairing between homologous chromocomes division. The mechamism that leads to precise point-by-point pairing between homologous chromosomes remains to be ascertained. Several items of information, however, suggest that chromsome alignment leading to synapsis may be mediated somehow by the nuclear membrane. Pachytene bivalents in eukaryotes are firmly attached to the inner niclear membrane at both termini. This attached begins with unpaired leptotene chromosomes that already have developed a lateral element. Once attached, the loptotene chromosomes begin to synapse. A number of different models have been proposed to account for genetic recombination via exchange between DNA strands following their breakage and subsequent reunion in new arrangement. One of the models accounting for molecular recombination leading to chromatid exchange and chiasma formation was first proposed in 1964 by Holliday, and 30 years later still a modified version of his model is favored. Nicks are made by endomuclease at corresponding sites on one strant of each DNA duplex in nonsister chromatid of a bivalent during prophase 1 of meiosis. The nicked strands loop-out and two strands reassociate into an exchanged arrangement, which is sealed by ligase. The remaining intact strand of each duplex is nicked at a site opposite the cross-over, and the exposed ends are digested by exonuclease action. Considerable progress has been made in recent years in the effort to define the molecular and organization features of the centromere region in the yeast chromosome. Centromere core region of the DNA duplex is flanked by 15 densely packed nucleosomes on ons side and by 3 packed nucleosomes on the other side, that is, 2000 bp on one side and 400 400 bp in the other side. All the telomeres of a given species share a common DNA sequence. Two ends of each chromosome are virtually identical. At the end of each chromosome there exist two kinds of DNA sequence" simple telpmeric sequences and telpmere-associated sequencies. Various studies of telomere replication, function, and behabior are now in progress, all greatly aided by molecular methods. During nuclear division in mitosis as well as in meiosis, the nucleili disappear by the time of metaphase and reappear during nuclear reorganizations in telophase. When telophase begins, small nucleoli form at the NOR of each nucleolar-organizing chromosome, enlarge, and fuse to form one or more large nucleoli. Nucleolus is a special structure attached top a specific nucleolar-organizing region located at a specific site of a particular chromosome. The nucleolus is a vertical factory for the synthesis of rRNAs and the assenbly of ribosome subunit precursors.sors.