• 한국미생물·생명공학회지
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• 제37권1호
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• pp.17-23
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• 2009

PCR법을 이용하여 Thermus thermophilus HJ6 유래 DNA polymerase(Tod) 유전자를 클로닝하고 염기서열을 분석한 결과, ORF는 2,505개의 뉴클레오타이드로 구성되고 834개의 아미노산을 암호화하였다. 아마노산 서열을 바탕으로 상동성을 분석한 결과, Thermus thermophilus HB8 유래 DNA polymerase와 98%, Thermus aquaticus 유래 DNA polymorase와 86%의 identity를 나타내었다. 이 유전자를 박테리오파지 $\lambda$ 유래 온도감수성 프로모터(PR, PL)를 포함하는 pJLA503 벡터를 이용하여 대장균에서 발현하였다. 발현된 효소는 열처리, $HiTrap^{TM}$ Q column과 $HiPrep^{TM}$ Sephacryl S-200 HR 26/60 columun으로 정제하여 94 kDa의 단백질을 얻을 수 있었다. 정제된 효소의 DNA 중합 활성에 대한 최적온도는 $75{\sim}80^{\circ}C$이고 최적 pH가 9.0이었다. $Mg^{2+}$ and $Mn^{2+}$에 대한 최적 농도는 각각 2.5mM과 1mM이었고 효소활성은 2가 양이온의 존재 하에서는 활성화 되지만 1가양이온에서는 저 해되었다. Tod DNA 중합효소를 이용한 PCR 실험결과, Tod DNA 중합효소는 DNA 증폭 및 PCR 관련 기술에 응용 가능할 것으로 생각된다.

• Journal of Dairy Science and Biotechnology
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• 제33권1호
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• pp.17-25
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• 2015

본 실험은 쌀겨를 발효식품에 이용하고자 상업용 균주인 Streptococcus thermophilus(ST-body1), Lactobacillus casei(LC-10)을 이용하여 발효유를 제조하고, 발효시간 경과에 따라 적정산도, 유산균수, 유기산 측정, 유리아미노산 측정, 관능검사를 측정하였다. ST-body1은 대조구와 처리구 모두 발효 3시간째에 급격하게 산도가 증가하였다. 하지만 LC-10은 산도의 증가폭이 크지 않아 24시간 발효를 하여도 산도가 0.5%를 넘지 못하였다. 균주의 생균수는 대조군과 실험군 모두 배양 24시간 동안 뚜렷한 경향 없이 $10^6{\sim}10^9CFU/mL$ 사이로 존재하였다. 유기산 및 유리아미노산 측정 결과, ST-body1 생장 및 생육에는 glutamic acid가 LC-10 생장 및 생육에는 aspartic acid가 밀접한 관계를 보였으며, LC-10은 발효 시 methionine이 20~30시간 경에 감소하다가 증가하는 것으로 보아 methionine을 발효 시 이용하고, 재생산하는 것으로 추측된다. 관능검사 결과, 선호도는 ST-body1이 미강의 존재 유무에 관계없이 우수하였다.

• 한국식품과학회지
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• 제18권6호
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• pp.492-496
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• 1986

환원탈지유배지에서 자란 Lactobacillus helveticus YM-1의 cell-free filtrate로부터 Streptococcus thermophilus CH-1의 생육촉진을 확인한 결과 이 물질은 분자량이 5,000정도의 peptide로 나타난다. 이 peptide 중에는 aspartic acid, Iysine, proline, leucine, valine, alanine, glutamic acid등의 amino산이 비교적 풍부하였으며, 그중에서 glutamic acid 함량이 가장 높았다. 또 이 Peptide가 생육 촉진효과 나타내는데 가장 중요한 역할을 담당하는 것은 glutamic acid와 Phenylalanine으로 판단되었다.

• Preventive Nutrition and Food Science
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• 제6권2호
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• pp.96-100
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• 2001

Mixtures prepared from whole milk with added skin milk powder(2.5%, w/v) and Angelica keiskei juice (1.5%, w/v) were fermented with lactic acid bacteria (single and mixed culture of Lactobacillus bulgaricus and Strpetococcus thermophilus) for 24 hours. The fermented mixtures (curd yogurt) were evaluated for acid production (pH and titratable acidity), cell numbers, viscosity, sensory property and keeping quality. Results indicated that the addition of Angelica keiskei stimulated the acid production by lactic acid bacteria. The number of viable cells reached 4.5~7.3$\times$10$^{9}$ CFU/mL for Angelica keiskei-added yogurts, while 3.3~5.1$\times$10$^{9}$ CFU/mL for control yogurts. Viscosity of Angelica keiskei-added yogurts was higher (3,609~3,854 centipoises) than that of control yogurts(3,346~3,700 centipoises). Of the microorganism tested, mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus was most effective in acid production. The overall sensory score showed that Angelica keiskei yogurt fermented with Streptococcus thermophilus was evaluated as good as control yogurt. When yogurts were stored at 4$^{\circ}C$ for 12 days, pH, titratable acidity and viable cells of lactic acid bacteria were not significantly changed(p<0.05).

• KSBB Journal
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• 제27권4호
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• pp.257-262
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• 2012

The gene encoding Thermus thermophilus HJ6 laccase (Tt-laccase) was cloned, sequenced, and comprised of 1,389 nucleotides encoding a protein (462 amino acids) with a predicted molecular mass of 51,049 Da. The deduced amino acid sequence of Tt-laccase showed 99.7% and 44.3% identities to the Thermus thermophilus HB27 laccase and Synechococcus sp. RS9917 laccase, respectively. Tt-laccase gene was expressed as a fusion protein with six histidine residues in E. coli Rosetta-gami (DE3) cells, and the recombinant protein was purified to homogeneity. UV-Vis spectrum analysis revealed that the enzyme has copper atoms, a type I Cu(II) and a type III binuclear Cu(II). The optimum pH for the oxidation of guaiacol was 5.0 and the optimum temperature was $90^{\circ}C$ The half-life of heat inactivation was about 120 min at $90^{\circ}C$ The enzyme reaction was inhibited by sodium azide, L-cystein, EDTA, dithiothreitol, tropolone, and kojic acid. The enzyme oxidized various known laccase substrates, its lowest $K_m$ value being for 4-hydroxyindole, highest $k_{cat}$ value for syringaldazine, and highest $k_{cat}/K_m$ for guaiacol.

• 한국식품조리과학회지
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• 제15권1호
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• pp.73-80
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• 1999

This study was carried out to investigate the effects of enzyme treatments on the functional properties of soy protein isolate (SPI) and to examine the quality attributes of soy yogurt prepared by different enzyme treatments, sweeteners and starter cultures. Enzyme treatment increased the solubility and emulsifying capacity of soy proteins, but decreased the emulsifying stability; the enzymatic activity of ${\alpha}$-chymotrypsin was higher than that of trypsin. Enzyme treatments decreased the pH of soy yogurts prepared by both culture methods, the culture of L. bulgaricus and S. thermophilus and the culture of L. bulgaricus and K. fragilis, but increased the titratable acidity, total numbers of lactic acid bacteria and yeast. Trypsin was more effective than ${\alpha}$-chymotrypsin in decreasing pH and increasing titratable acidity and total numbers of lactic acid bacteria and yeast. Fructose decreased the pH of soy yogurts more than sucrose in the culture of L. bulgaricus and S. thermophilus, and vice versa in the culture of L. bulgaricus and K. fragilis. Fructooligosaccharides were more effective in the culture of L. bulgaricus and K. fragilis than in the culture of L. bulgaricus and S. thermophilus in increasing the titratable acidity, total count of lactic acid bacteria and yeast. In sensory evaluation, soy yogurts containing trypsin treated SPI, fructose and fructooligosaccharides (75%:25%) were more acceptable than those containing untreated or trypsin treated SPI and fructose. This was because of more smooth and less sour, in which the values of pH, titratable acidity, microbial growth, and viscosity were in the range of commercial yogurts. Soy yogurts fermented by L. bulgaricus and K. fragilis showed more smooth mouthfeel than those fermented by L. bulgaricus and S. thermophilus.

• 한국미생물·생명공학회지
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• 제17권1호
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• pp.35-45
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• 1989

Streptococcus thermophilus 510으로부터 $\beta$-galactosidase의 생성조건은 탄소원으로 0.5% lactose를 첨가한 배지에서 초기 pH7.0, 배양온도 37$^{\circ}C$, 배양기간 18시간이었다. 배양여액으로부터 $\beta$-galactosidase를 ammonium sulfate 분획, 핵산의 제거, Sephadex G-200 gel filtration 및 DEAE-Sephadex A-50 ion exchange chromatography 등의 4단계 정제과정을 거쳐 정제한 결과 18배 정제되어 단일 단백질로 분리되었다. 정제효소의 활성 최적온도는 5$0^{\circ}C$, 최적 pH는 7.0이었고, 효소활성이 Mn$^{2+}$, $K^+$과 같은 금속이온과 dithiothreitol, 2-mercaptoethanol에 의해 촉진되었고, Hg$^{2+}$, $Zn^{2+}$, Co$^{2+}$, $Ca^{2+}$, EDTA, 8-hydroxyquinoline, galactose 등에 의해 저해되었다. 효소의 분자량이 520,000, 합성기질인 ONPG에 대한 $K_{m}$ 은 1,25mM, V$_{max}$는 88.50 $\mu$mole/min.mg protein이었고, 주종 아미노산은 glutainic acid, aspartic acid, leucine 및 valine이었다.

• Journal of Microbiology and Biotechnology
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• 제28권10호
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• pp.1581-1588
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• 2018

The growth of lactic acid bacteria (LAB) generates a high number of metabolites related to aromas and flavors in fermented dairy foods. These microbial proteases are involved in protein hydrolysis that produces necessary peptides for their growth and releases different molecules of interest, like bioactive peptides, during their activity. Each genus in particular has its own proteolytic system to hydrolyze the necessary proteins to meet its requirements. This review aims to highlight the differences between the proteolytic systems of Streptococcus thermophilus and other lactic acid bacteria (Lactococcus and Lactobacillus) since they are microorganisms that are frequently used in combination with other LAB in the elaboration of fermented dairy products. Based on genetic studies and in vitro and in vivo tests, the proteolytic system of Streptococcus thermophilus has been divided into three parts: 1) a serine proteinase linked to the cellular wall that is activated in the absence of glutamine and methionine; 2) the transport of peptides and oligopeptides, which are integrated in both the Dpp system and the Ami system, respectively; according to this, it is worth mentioning that the Ami system is able to transport peptides with up to 23 amino acids while the Opp system of Lactococcus or Lactobacillus transports chains with less than 13 amino acids; and finally, 3) peptide hydrolysis by intracellular peptidases, including a group of three exclusive of S. thermophilus capable of releasing either aromatic amino acids or peptides with aromatic amino acids.

• 한국축산식품학회지
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• 제35권5호
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• pp.683-691
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• 2015

The objective of this study was to identify the coccoidal bacteria present in 188 samples of fermented yaks’, mares’ and cows’ milk products collected from 12 different regions in Mongolia. Furthermore, we evaluated the fermentation properties of ten selected isolates of the predominant species, Streptococcus (S.) thermophiles, during the process of milk fermentation and subsequent storage of the resulting yoghurt at 4℃. Overall, 159 isolates were obtained from 188 samples using M17 agar. These isolates were presumed to be lactic acid bacteria based on their gram-positive and catalase-negative properties, and were identified to species level using 16S rRNA gene sequence analysis. These coccoid isolates were distributed in four genera and six species: Enterococcus (E.) durans, Enterococcus (E.) faecalis, Lactococcus (Lac.) subsp. lactis, Leuconostoc (Leuc.) lactis, Leuconostoc (Leuc.) mesenteroides. subsp. mesenteroides and S. thermophilus. Among these S. thermophilus was the most common species in most samples. From evaluation of the fermentation characteristics (viable counts, pH, titratable acidity [TA]) of ten selected S. thermophilus isolates we could identify four isolates (IMAU 20246, IMAU20764, IMAU20729 and IMAU20738) that were fast acid producers. IMAU20246 produced the highest concentrations of lactic acid and formic acid. These isolates have potential as starter cultures for yoghurt production.

• 한국미생물·생명공학회지
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• 제38권2호
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• pp.158-162
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• 2010

고온균 Thermus thermophilus HJ6 유래의 N-말단 결실 Tod polymerase($\Delta$Tod polymerase)는 온도 감수성 프로모터 (lambda pR and pL)를 포함하는 pJLA503 벡터를 이용하여 대장균에서 발현하였다. N-말단 250개 아미노산이 제거된 $\Delta$Tod polymerase는 5'$\rightarrow$3' exonuclease 활성은 없어지고 DNA 중합반응의 활성은 그대로 유지되었다. $\Delta$Tod polymerase는 $MgCl_2$의 존재 하에서 매우 효율적으로 역전사 반응과 PCR 반응을 수행하였다. 또한 $\Delta$Tod polymerase는 one-step RT-PCR 반응에서 Taq polymerase 보다 높은 cDNA 증폭 효율을 나타내었다.