• Journal of Microbiology and Biotechnology
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• 제6권6호
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• pp.432-438
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• 1996

Native crystalline chitin was hydrolyzed in an agitated bead reaction system using crude chitinase excreted from Aspergillus fumigatus JC-19. The reaction was enhanced significantly, and the concentration and yield of reducing sugar after 48 hours were measured to be 35.42 g/I (w/v) and 0.64, respectively, around 1.86 times higher than those of the conventional system that was carried out without glass beads. The effect of reaction conditions, such as the amounts of chitin, chitinase and glass beads, and the size of glass bead, were examined. Ball milled chitin was also hydrolyzed in the agitated bead reaction system, the conversion yield and reaction rate of ball milled chitin for 24 hours increased up to 0.87 and 48.02 g/I, respectively. Chitinase showed relatively high stability in the agitated bead reaction system, particularly in the presence of enzyme stabilizer, $Ca^{++}$, which played a critical role in preventing the deactivation of chitinase by the physical impact of glass beads. The variations of the structural features of chitin during the reaction were followed by SEM and X-ray diffraction, and the enhanced hydrolysis reaction was caused by both the fragmentation of chitin particles and the destruction of the crystalline structure owing to the synergic effects of the attrition of glass beads and the hydrolytic action of chitinase.

• 한국인쇄학회지
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• 제20권1호
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• pp.65-78
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• 2002

The suspension polymerization of styrene was carried out to obtain the narrow-size distribution of particle by using poly(vinyl alcohol) (PVA) as suspension stabilizer according to the degree of hydrolysis and the molecular weight. The stabilizing properties of suspension are also dependent on the interfacial tension of aqueous solution when PVA is added. When the polymerization process was carried out with low hydrolyzed PVA, it gave single, well-defined particles, while high hydrolyzed PVA gave clusters. The size of particle produced in this study ranged between 5${\mu}{\textrm}{m}$ and 10${\mu}{\textrm}{m}$. The suspending agent, PVA, influences on the drop size and drop stability, When the molecular weight of PVA is increased, the drop size decreases and the drops become more stable toward coalescence. An increase in the PVA concentration decreases the mean drop size and narrows the drop size distribution.

• Korean Chemical Engineering Research
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• 제49권5호
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• pp.516-520
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• 2011

휴대용 고분자전해질 연료전지의 수소발생용으로써 $NaBH_4$는 많은 장점을 갖고 있다. 본 연구에서는 $NaBH_4$ 가수분해 반응의 수소 수율에 대해 연구하였다. $NaBH_4$ 가수분해 반응의 수소 수율에 미치는 촉매 형태, 온도, $NaBH_4$ 농도, NaOH 농도 등의 영향에 대해 실험하였다. 촉매는 Co-P/Cu, Co-B/Cu와 Co-P-B/Cu를 사용하였는데 이들 촉매 종류에 따라 $NaBH_4$ 가수분해 반응의 수소 수율에 미치는 영향은 거의 없었다. $60^{\circ}C$ 이하의 온도에서 $NaBH_4$ 농도가 증가하면 부산물과 $NaBH_4$에 의해 겔이 형성되면서 가수분해 반응의 수소 수율이 감소였다. 겔 형성에 의해서 $NaBH_4$ 가수분해 반응 속도와 수소 총 발생량이 감소하였다. 안정화제인 NaOH를 첨가하면 겔 형성을 촉진해 수소 수율을 감소시켰다.

• 공업화학
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• 제26권1호
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• pp.86-91
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• 2015

BHT (2,6-di-tert-butyl-4-methylphenol), TBC (4-tert-butylcatechol), 스테아린산구리 등 여러 가지 중합방지제를 사용하여 MPPO (3-methyl-1-phenyl-2-phospholene-1-oxide)를 제조하였다. 제조한 시료에 대해 FTIR, $^1H$-NMR, GC/MS 등을 이용하여 분석한 결과 중합방지제의 종류에 관계없이 MPPO 합성이 확인되었다. 반응 시간이 증가하면 MPPO의 수율은 증가하지만, 순도는 약간 저하하는 경향을 보였다. 합성 온도가 높아지면 MPPO의 수율과 순도가 증가하였지만, 스테아린산구리를 사용한 경우 MPPO의 순도 변화는 나타나지 않았다. 중합방지제 양이 증가하면 MPPO의 수율은 변화가 나타나지 않았다. 순도는 중합방지제 양이 증가하면 증가하였지만, BHT를 사용한 경우에는 중합방지제 양에 따른 MPPO의 순도 변화가 없었다. Diphenylcarbodiimide 합성에 대한 MPPO의 촉매 활성은 스테아린산구리를 사용하여 제조한 MPPO가 가장 높았다.

• 한국축산식품학회지
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• 제30권4호
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• pp.575-581
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• 2010

This investigation was aimed at developing a ready-to-reconstitute beverage by utilizing probiotics and whey protein hydrolysates carrying bioactive peptides. Cheddar cheese whey was ultrafiltered. The 18% protein retentate was subjected to protein hydrolysis using Neutrase. The hydrolyzed retentate was further condensed to 35% total solids and spray-dried at $75^{\circ}C$ outlet air temperature. Different levels of sugar, citric acid and stabilizer were blended for spray-dried hydrolysates. Spray-dried hydrolysate was further inoculated with different levels of probiotics grown in a whey medium and dried in fluidized-bed drier at $40^{\circ}C$ to obtain a ready-to-reconstitute beverage. Hydrolysis was greatest at an enzyme:substrate ratio of 1:25 for 3 h. Spray-dried hydrolysate reconstituted to 1% protein and blended with 15% sugar, 0.2% citric acid and 0.15% xantham gum resulted in a superior product with no sedimentation. Accordingly, sugar, citric acid and xanthum gum were dry-blended with spray-dried hydrolysates. Bifidobacterium bifidum and Lactobacillus acidophilus that was grown separately in a whey medium, blended to produce 2% spray-dried hydrolysate and dried as described above resulted in a readyto-reconstitute beverage mix. The fluidized dried product typically exhibited a probiotic count of $10^8$colony forming units (CFU)/g. However, blending of probiotic to the retentate and direct spray-drying precipitously reduced the probiotic count to $10^4$ CFU/g of powder.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1534-1538
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• 2011

Uniform, hollow nanosilica spheres were prepared by the chemical coating of cationic polystyrene (cPS) with tetraethylorthosilicate (TEOS), followed by calcination at 600 $^{\circ}C$ under air. cPS was synthesized by surfactant-free emulsion polymerization using 2,2'-azobis (2-methyl propionamidine) dihydrochloride as the cationic initiator, and poly(vinyl pyrrolidone) as a stabilizer. The resulting cPS spheres were 280 nm in diameter, and showed monodispersion. After coating, the hollow silica product was spherically shaped, and 330 nm in diameter, with a narrow distribution of sizes. Dispersion was uniform. Wall thickness was 25 nm, and surface area was 96.4 $m^2/g$, as determined by BET. The uniformity of the wall thickness was strongly dependent upon the cPS surface charge. The effects of TEOS and ammonia concentrations on shape, size, wall thickness, and surface roughness of hollow $SiO_2$ spheres were investigated. We observed that the wall thicknesses of hollow $SiO_2$ spheres increased and that silica size was simultaneously enhanced with increases in TEOS concentrations. When ammonia concentrations were increased, the irregularity of rough surfaces and aggregation of spherical particles were more severe because higher concentrations of ammonia result in faster hydrolysis and condensation of TEOS. These changes caused the silica to grow faster, resulting in hollow $SiO_2$ spheres with irregular, rough surfaces.

• 한국식품과학회지
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• 제23권4호
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• pp.471-477
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• 1991

치즈 제조시 생기는 유청을 reverse osmosis를 이용하여 농축한 후, 이로부터 유청음료를 제조하기 위한 최적조건을 조사하였다. 유당 가수분해도와 산생성은 Str. thermophilus와L. bulgaricus의 혼합균주가 Str. cremoris와 Str. lactis의 혼합균주에 비해 효율적이었다. 유청의 유당농축비율(LCR)이 증가할수록 적정산도는 증가하였으나 pH의 저하는 억제되었다. 원심침전량을 조사한 결과 LCR에 관련없이 모두 비슷한 수준이었으나 자연침전량의 경우 LCR 3.0 : 1은 침전이 거의 없었다. 안정제로서는 PGA가 가장 적합하였으며 LCR 3.0 : 1의 경우 0.l% 이하의 농도에서도 침전을 방지할 수 있었다. 감미료는 aspartame, 향료로는 yoghurt향이 가장 적합하였다.

• 한국세라믹학회지
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• 제40권4호
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• pp.385-392
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• 2003

Sol-gel preparation technique using a chemical reaction of metal alkoxides has been widely used for the fabrication of various materials including ceramics. However, its mechanism has been studied till now because a number of chemical ways are possible from various alkoxides and additives. In this study, the mechanism of hydrolysis, condensation, and polymerization of alkoxides were investigated from the fabrication of lead-zirconate-titanate (PbZr$\_$x/Ti$\_$l-x/O$_3$; PZT) thin film that is used as various micro-actuator, transducer, and sensor because of its high electro-mechanical coupling factors and thermal stability. Furthermore, the fabrication process and characteristics of self-patternable PZT film using photosensitive stabilizer were studied in order to resolve the problem of physical damage and properties degradation during dry etching for device fabrication. Using an optimum condition to prepare the self-patternable PZT film, more than 5000 ${\AA}$ thick self-patternable PZT film could be fabricated by three times coating. The PZT film showed 28.4 ${\mu}$c/cm$^2$ of remnant polarization (Pr) and 37.0 kV/cm of coercive field (E$\_$c/).

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.677-681
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• 2015

$NaBH_4$ 가수 분해용 경량반응기의 재질로서 알루미늄 합금을 검토하였다. 알루미늄은 알칼리에 용해되는데, $NaBH_4$ 반응 용액중에 안정화제로 NaOH가 포함되어 있다. 알루미늄의 부식 속도를 낮추기 위해서 NaOH 농도를 낮추면 저장중에 $NaBH_4$가 손실된다. 그래서 최적의 NaOH 농도를 결정할 때 알루미늄 부식과 $NaBH_4$ 안정화를 모두 고려해야 한다. $NaBH_4$ 안정화와 알루미늄 부식속도는 수소발생속도에 의해 측정하였다. $NaBH_4$ 안정화는 $20{\sim}50^{\circ}C$에서 알루미늄 부식속도는 $60{\sim}90^{\circ}C$ 온도에서 실험하였다. 알루미늄 부식과 $NaBH_4$ 안정화를 모두 고려한 최적의 NaOH농도는 0.30 wt% 였다. 알루미늄 합금 6061를 사용해 반응기 온도 $80{\sim}90^{\circ}C$에서 NaOH 0.3 wt%로 200분간 반응을 진행하였다.

• Korean Chemical Engineering Research
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• 제55권1호
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• pp.13-18
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• 2017

무인항공기용 고분자전해질 연료전지의 수소발생용으로써 $NaBH_4$는 많은 장점을 갖고 있다. 무인항공기용으로 이용하기 위해서는 $NaBH_4$ 가수분해 반응 후 부산물의 무게와 부피가 작아야 한다. 그래서 본 연구에서는 비담지 촉매를 사용한 $NaBH_4$ 가수분해 반응 후 부산물의 무게와 부피에 대해 연구하였다. 촉매 형태, $NaBH_4$ 농도, NaOH 농도, 촉매팩 두께 등이 부산물의 무게와 부피에 미치는 영향에 대해 연구하였다. 본 실험 조건에서 발생한 부산물은 대부분 $NaB(OH)_4$였고, 거품이 발생하여 부피가 증가하였다. 안정화제인 NaOH 농도는 부산물의 무게와 부피에 별 영향을 주지 않았다. $NaBH_4$ 농도가 증가하면 부산물 무게가 감소하였으나, $NaBH_4$ 농도 23 wt%에서 최고 부피를 나타냈다. 소포제를 이용해 부산물의 부피를 감소시킬 수 있었다.