α-Galactosidase 에 의한 Bifidobacteria 균수 측정에 관한 연구

강국희,이시경,백운화,민해기 成均館大學校 科學技術硏究所 1992 論文集 Vol.43 No.2

This method using the synthesis substrate of 5-bromo-4-chloro-3 indolyl-galactoside (X-a -Gal) was examined for the differential enumeration of Bifidobacteria and lactic acid producing bacteria. Bifidobacteria possess a high level of a-galactosidase activity. Bifidobacterium longum KCTC 3215 exhibited the highest a- galactosidase specific activity (8.57 units/mg protein). Determination of a -galactosidase activity using the PNPG procedure showed that Lactobacillus, Streptococcus, Pediococcus, and Leuconostoc strain had lower a-galactosidase activity as compared to Bifidobacteria. The X-a- Gal based medium is useful to identify Bifidobacteria among lactic acid producing bacteria since the enzyme action of a-galactosidase hydrolysis X-a-Gal substrate and releases indol which impacts a blue color to Bifidobacterial colonies on agar plates. All strains of Bifidobacteria appeared blue colonies on MRS agar medium supplemented with 100 uM X- a - Gal while colonies of other lactic acid producing bacteria appeared white or light blue.

Lactobacillus Casei Bacteriophage의 pH에 대한 안정성

姜國熙,朴基文,尹快炳 成均館大學校 1982 論文集 Vol.31 No.-

Survivability of the phages active on the Lactobacillus casei YIT 9018 was studied in skimmiik at various pH. The phages of J1, φ1, TK93, PD2, and PD5 was used for this experiment. Decreases in phage titer in skimmilk at pH 4.0 were observed for 48 hrs. Viability of the phages was not changed for 7 days through the pH range of 8.0 to 5.0. At pH9.0, the titer reduction of phage TK93 was remarkably.

Semiconductor Gas Sensor를 이용한 유산발효중 휘발성 화합물의 측정

강국희 성균관대학교 생명과학자원연구소 1997 生命資源科學硏究 Vol.4 No.2

The measuring instrument using gas sensor was developed to determine the changes of components in lactic culture during fermentation. The gas sensor was installed in the waterbath to protect from effect of external temperature and the temperature of the waterbath was maintained as 37℃. Volatile flavor components from lactic fermentation moved to semiconductor gas sensor by carrier gas and the sensor responsed as different signal. The different signal of the sensor produced by electric pressure. The changes of the signal showed a similar tendency with those of acidity and the concentration of volatile flavor components during fermentation. The sensitivity of the sensor was highest when the velocity of the carrier gas was 30m1/min. Therefore, the gas sensor can be used to monitor and control the fermentation process.

Bifidobacterium angulatum으로부터 α-galactosidase의 정제 및 특성

강대중,민해기,강국희 成均館大學校 科學技術硏究所 1993 論文集 Vol.44 No.1

α-galactosidase는 (α-D-galactoside galactohydrolase: EC 3.2.1.22)는 다당류나 올리고당인 melibiose, raffinose, stachyose와 guar gum 등의 α-galactosidic 결합을 하고 있는 당을 분해하는 효소이다. 장내세균중 우익균이며 우세균주인 Bifidobacteria로부터 α-galactosidase의 효소학적 특성을 알아보기 위하여 배양여액으로부터 ammonium sulfate분획, 핵산의 제거, Sephadex G-200 gel filtration 및 DEAE-Sephadex A-50 ion exchange chromatography 등의 4단계 정제과정을 거쳐 정제한 결과 약 8배로 정제되어 단일 단백질로 분리하였다. 또한, 효소분해산물을 알아보기 위하여 TLC에 의하여 당분해 및 올리고당의 생성을 알아보았다. 정제효소의 활성 최적온도는 37℃, 최적 pH는 7.0이었다. 효소활성이 K^+, Zn^2+과 같은 금속이온과 8-Hydroxyquinoline, Sodium Bisulfite 등에 의해선 그다지 저해되지 않았으나, Hg^+, Cu^2+과 p-Chloromercuribenzoic acid에 의해선 저해되었다. 효소의 분자량이 301, 995, 합성기질인 PNPG에 대한 K_m은 0.069mM, V_max는 347.22μmol/min.mg protein이었다. To elucidate enzymatic properties of α-galactosidase (EC 3.2.1.22) from Bif.angulatum. α-galactosidase was purified to homogeneity by ammonium sulfate fractionation, protamine sulfate precipitation, sephadex G-200 gel filtration, and DEAE-sephadex A-50 ion exchange chromatography. The purified α-galactosidase was found tobbe homogeneous by SDSpolyacrylamide gel electrophoresis. The molecular weight of this enzyme, estimated by sepadex G-200 gel filtration, was about 301,995. The optimum conditions for the enzyme reaction was pH 6.5 to 7.0 at 37℃. The purified enzyme was stable at 45℃ or below and in buffer at pH 6 to 7.0. The activity was inhibited by mercury, copper ion, and p-chloromercuribenzoic acid. The kinetics of this enzyme, with p-nitrophenyl-α-D-galactoside as substrate, was determined : K_m was about 0.069mM and V_mas was 347.22 μmoles/min mg protein.

김밥과 그 재료의 세균수 측정

강국희,김혜란,고애경,김경민,최선규 성균관대학교 생명과학자원연구소 1994 生命資源科學硏究 Vol.1 No.2

We have investigated the distribution of bacteria in kimbab and its materials. The total bactria counts were over 3×10 exp(6)/g(n=30) when the kimbabs were delivered to restaurant and it exceeded the prieliminary legal level 1 × 10 exp(6)/g even though it should be negative for coliforms. In order to look into the cause of bacterial contamination in kimbabs, we examined the content materials of kimbabs. The bacterial counts were founded 10^4-10^8/g for Kim, 10^4-10^8/g for sausage, 10^4-10^6/g for spinach, 10^3-10^7/g for carrot, and 10^3-10^6/g for danmugi, respectively. From these results it could be concluded that the bacterial contamination in Kimbabs are due to kim, spinach, carrot, and sausage. Therefore, so as to reduce the bacterial contamination for kimbab, the sanitary manufacture and storage of kim and the refrigeration of content materials should be went abreast.

Str.thermophilus 510의 β-Galactosidase 유전자의 Cloning 및 대장균에의 발현

강국희,민해기,이호근,성문희 成均館大學校 科學技術硏究所 1992 論文集 Vol.42 No.2

Chromosomal DNA from Str. thermophilus 510 was purified and cleaved with the restriction enzyme PstI. Chromosomal DNA was ligated to pBR322 for transformation into E. coli JM109. A β-galactosidase positive clone was detected by its blue color on a medium supplemented with 5-bromo-4-chloro-3-indolyl-β-D-galactoside. This transformat possessed a single plasmid, designated pSK 001, which contained, in addition of the vector DNA, A 7.0Kb Pst I insertion fragment coding for β-gal activity. A restriction enzyme map of pSK 001 was consist of Hind Ⅲ, EcoR I, Bgl Ⅱ, Sal I, Pvu Ⅱ, etc. An extract from E. coli JM109 (pSK001) contained a β-gal protein with the same electrophoretic mobility as the β-gal from Str. thermophilus 510.

Limulus Amoebocyte Lysate법에 의한 원유와 살균유의 세균수 측정

姜國熙,王智怨,朴興洙,李圭鍾,金敬民 成均館大學校 科學技術硏究所 1993 論文集 Vol.44 No.2

LAL method for the determination of Gram-negative bacterial Lipopolysaccharides(LPS) in milk is proposed and its value for bacteriological quality control is investigated. The relationship between the LPS contents and total colony count(cfu/ml), which covers the Gram-negative bacteria, was determined in raw milk samples. The coefficient of correlation between Gram-negative bacterial counts(cfu/ml) and LPS contents was r^2 =0.969. And, the correlation coefficient between total bacterial counts(cfu/ml) and LPS contents was r^2 =0. 914. It was also investigated how much the LPS contents were in UHT milks from l0 different dairy industrial companies in Korea. It varied from 92 ng LPS/ml to 938 ng LPS /ml.

GOS가 장내 Bifidobacteria의 생육촉진에 미치는 영향에 관한 연구

강국희,문지웅,강대중,이재영 成均館大學校 科學技術硏究所 1993 論文集 Vol.44 No.2

We investigated the growth effect of various sugars on the principal intestinal microorganisms which were Bifidobacteria, Lactobacilli, Streptococci, Clostridia, Escherichia, Eubacteria, and Staphylococci. Those microorganisms were cultivated on media containing various sugars. The sugars were grouped into A, B, and C. Group A consisted of sugars extracted by water, 5%, 15%, 30%, and 40%, EtOH, respectively. Group B were galactooligosaccharide(GOS), fructooligosaccharide(FOS), isomaltooligosaccharide(IMO), and xylooligosaccharide( XOS). Group C were LOS, SOS, and LSOS. Bif. adolescentis, Bif. bifidum, Bif. infantis, Bif. longum, and Str. faecalis grew well on the media containing sugars of each A, B, and C group, while C. butyricurm, S. aureus, Eu. limosum, and E. coli did not. The results indicated that oligosaccharides of A, B, and C group were consumed effectively by Bifidobacterium spp. but not utilized by other intestinal microorganisms. Oligosaccharides of each A, B, and C group promoted selectively the growth of Bif. infantis and Bif. longum in the human intestinal microflora.

原乳의 세균수 等級制 실시에 따른 미생물학적 품질개선

姜國熙,朴信仁,鄭忠一 성균관대학교 생명과학자원연구소 1994 生命資源科學硏究 Vol.1 No.2

Raw milk grading system based on the bacterial count was started in Korea from June 1, 1993. The production ratio of first class which has 100,000/ml below in the bacterial counts of raw milk increased from 21% to 60% during 6 months. But, the ratio of the first class which has 250,000/ml below in the somatic cells did not change and became to be worse. In somatic cells the ratio of the first class milk was 42% in June 1993 and after 6 months it was decreased to 30%, Because current grade system based on the somatic cells give an penalty only to the off-grade milk which contains more of 750,000cell/ml. The system should be changed to pay different money according to the different classes of somatic cells in the raw milk.

乳固形分의 농도에 다른 乳酸菌의 生育

姜國熙,李春花 成均館大學校 科學技術硏究所 1992 論文集 Vol.42 No.2

Influence of Solid-Not-Fat concentration on the growth of lactic acid bacteria was investigated in skim milk medium. The cultivation at optimum temperature of each strains was not significant with the various concentration of SNF 10%, 13%, 16%. The viable cell counts of Lac. bulgaricus and Lac. helveticus reached to maximum level of 10^9/ml in 24 hrs incubation and did not counted in 5 days incubation at 40℃. When the cultures (10^9/ml) stored at 30℃, viable cells remained 10^7-8/ml in 7 days. Survival of Lac. acidophilus culture was sustained high level at its optimum temperature for 7 days.