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호알칼리성 Bacillus firmus가 생산하는 $\beta$-Cyclodextrin Glucanotransferase의 정제 및 효소반응 특성
신현동,김찬,이용현,Shin, Hyun-Dong,Kim, Chan,Lee, Yong-Hyun 한국미생물·생명공학회 1998 한국미생물·생명공학회지 Vol.26 No.4
호알카리성 Bacillus firmus var. alkalophilus가 생산하는 cyclodextrin glucanotransferase(CGTase)를 호화시킨 팽윤감자전분을 이용한 흡착 및 탈착, 한외여과, DEAE-cellulose 이온교환 크로마토그래피, 그리고 Sephacryl HR-100을 이용한 gel filtration 등의 분리정제 과정을 통하여 정제하였다. 정제된 CGTase의 분자량은 약 77,000 Da이었으며, 등전점은 6.2~6.3이었다. 최적 효소반응 온도 및 pH는 각각 5$0^{\circ}C$ 와 6.0 였고, 열 및 pH 안정성은 5$0^{\circ}C$까지와 pH 6.0~9.5 사이였다, 정제된 CGTase는 $Ca^{2+}$ 에 의하여 열 안정성이 크게 상당히 향상되었으며 최적 효소반응 온도와 열 안정성도 55~6$0^{\circ}C$와 6$0^{\circ}C$로 증가하였다. CGTase의 기질 특이성을 검토한 결과 여러 종류의 전분들로부터 $\beta$-CD를 주로 생성하였으며, ${\gamma}$-CD도 소량 생성하였으나 $\alpha$-CD는 거의 생성되지 않았다. Sweet potato starch, corn starch, 그리고 amylopectin을 기질로 할 때 높은 CD전환율을 보였으며 $\beta$-CD와 ${\gamma}$-CB의 생성비가 5.8~8.4:1로서 $\beta$-CD를 고 수율로 생산하는 전형적인 $\beta$-type의 CGTase였다. 또한 본 효소의 최적 CD 생산조건은 기질농도 5.0%(w/v) corn starch, 효소첨가량 25 unit/g of starch로서 반응 8시간 후의 전체 CD량도 약 25 g/l로서 전환율은 50%였고, 이 때 $\beta$-CD농도는 21 g/l로서 전체 CD 중 84% 였다. Cyclodextrin glucanotransferase (CGTase) was purified from the culture broth of the Bacillus firmus var. alkalophilus, using ultrafiltration, starch adsorption/desorption, ion-exchange chromatography on DEAE-cellulose and gel filtration on Sephacryl HR-100. The molecular weight of the purified enzyme was determined as 77,000 by SDS-PAGE. The optimum pH and temperature for the CD synthesis were 6.0 and 5$0^{\circ}C$, respectively. The activity of this enzyme was stably kept at the range of pH 6.0~9.5 and up to 5$0^{\circ}C$. However, in the presence of $Ca^{2+}$, the optimum temperature for CD synthesis was shifted 55~6$0^{\circ}C$ and this enzyme was stable up to 6$0^{\circ}C$ because of the stabilizing effect of $Ca^{2+}$. The purified CGTase produced CDs with high conversion yields of 45~51% from sweet potato starch, com starch and amylopectin as substrate, especially, and the product ratio of $\beta$-CD to ${\gamma}$-CD was obtained at range of from 5.8:1 to 8.4:1 according to the kind of substrate. The purified enzyme produced mainly $\beta$-CD without accumulation of $\alpha$-CD during enzyme reaction using various starches as the substrate, indicating that the purified enzyme is the typical $\beta$-CGTase. The purified CGTase produced 25 g/l of CDs from 5.0% (w/v) liquefied com starch and the conversion yield of CDs was 50%, and the content of $\beta$-CD was 84% of total CDs after 8 hours under the optimum reaction condition.ion.
평판에 충돌하는 펄스파에 미치는 관출구 부분폐쇄의 영향
신현동(Hyun-Dong Shin),이영기(Young-Ki Lee),김희동(Heuy-Dong Kim),?戶口俊明(Toshiaki Setoguchi) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
When a shock wave arrives at a duct, an impulsive wave is discharged from the duct exit and causes serious noise and vibration problems. In the current study, the characteristics of the impulsive wave discharged from a partial closed duct exit is numerically investigated using a CFD method. The Yee-Roe- Davis’s total variation diminishing(TVD) scheme is used to solve the axisymmetric, unsteady, compressible Euler equations. With several partial closed duct exits, the Mach number of the incident shock wave M<SUB>s</SUB> and the distance L/D between the duct exit and a flat plate are varied in the range of M<SUB>s</SUB> = 1.01 ~ 1.50 and L/D = 1.0 ~ 4.0, respectively. The results obtained show that the magnitude of the impulsive wave impinging upon the flat plate strongly depends upon M<SUB>s</SUB>, L/D and the partial closure of duct exit. The impulsive wave on the flat plate can be considerably alleviated by the partial closure of duct exit and, thus, the present method can be a passive control for the impulsive wave.