• 상하수도학회지
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• 제18권6호
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• pp.785-793
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• 2004

Coagulation has been investigated for pretreatment of low-pressure membrane systems such as microfiltration and ultrafiltration. Coagulation pretreatment can reduce foulants (particles and organic matter) prior to membrane filtration. However, when in-line coagulation or submerged type of filtration is used, flocculent aggregates could act as a foulant depending on concentrations and specific properties of floc. A natural water and three synthetic waters were used to investigate effects of coagulation pretreatment and presence of flocculent aggregates on membrane fouling. Coagulation pretreatment shows that foul ants were effectively removed during coagulation and the formed cake layer on the membrane surface had less resistances compared to raw natural water. In addition, little difference in membrane fouling was found by flocculent aggregates from the natural water. Interestingly, however, the results by three synthetic waters indicated that flocculent aggregates could have adverse effects on membrane fouling in a specific condition.

• Journal of Microbiology and Biotechnology
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• 제9권1호
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• pp.39-43
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• 1999

A flocculent aggregate produced by Lactococcus lactis subsp. lactis in broths containing Tween 80, including MRS broth, had a microscopic structure of intertwined thread-like filaments. The filamentous structure was not elongated bacterial cells, but consisted of an organic solvent-soluble portion and an insoluble solid. L. lactis subsp. lactis grown at $25^{\circ}C$ for 15 days in tryptic soy broth with 0.1% Tween 80 and 1.0% malt extract produced 13 mg/l of flocculent aggregate, which contained 0.84 g/g of organic solvent-soluble component. The organic solvent-soluble part was identified as 10-hydroxyoctadecanoic acid.

• KSBB Journal
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• 제25권2호
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• pp.179-186
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• 2010

응집성 효모인 S. cerevisiae ATCC 96581를 이용한 최적의 에탄올 생산 공정 전략에 대하여 연구하였다. 효모의 특성을 고려하여, 효모 응집공정이 있는 반복 유가식 공정을 설계하였고, 이때 비멸균 포도당 분말을 매 12시간 마다 첨가하였고, 새로운 feeding medium을 24시간 혹은 36시간마다 세포 응집 후 교체 하였다. 이때 효모 응집이 없는 반복 유가식 공정과 비교 검토하였다. 최종적으로 24시간마다 세포를 응집시키고 상층배지를 제거하고 새로운 배지를 넣으면서 반복 유가식 에탄올 생산을 하는 것이 최적의 조건임을 알 수 있었고, 이때 120시간 동안 825 g의 에탄올을 생산 할 수 있었다.

• 한국미생물·생명공학회지
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• 제11권1호
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• pp.33-38
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• 1983

에타놀을 생산하는 Flocculent 균주는 균체순환을 위한 외부적인 장치 없이도 발효조 내부 자체에서 고농도의 균체를 유지시킬 수 있는 장점이 있다. 본 연구에서는 Flocculation 특성을 가지고 있는 Saccharomyces uvarum을 사용하여 Glucose 배지에서 회분식 및 연속식 발효특성을 고찰하였고 에타놀 발효의 수학적 모델을 만들었다. 이를 이용하여 여러 온도 및 pH에 따른 발효특성을 비교 검토한 결과 균체성장과 에탄올 생산의 최적온도는 33~35$^{\circ}C$ 이었고 pH 에 대한 영향은 그리 크지 않았으나 pH5가 최적 조건이었다. 이러한 환경적 최적 조건하에서 Semi-batch 발효에 의한 에타놀 최고 생산성은 12g/$\ell$/h이었다.

• 천문학회지
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• 제46권3호
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• pp.141-149
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• 2013

We analyze the spiral structure of 1725 nearby spiral galaxies with redshift less than 0.02. We use the color images provided by the Sloan Digital Sky Survey. We determine the arm classes (grand design, multiple-arm, flocculent) and the broad Hubble types (early, intermediate, late) as well as the bar types (SA, SAB, SB) by visual inspection. We find that flocculent galaxies are mostly of late Hubble type while multiple-arm galaxies are likely to be of early Hubble type. The fractional distribution of grand design galaxies is nearly constant along the Hubble type. The dependence of arm class on bar type is not as strong as that of the Hubble type. However, there is about a three times larger fraction of grand design spirals in SB galaxies than in SA galaxies, with nearly constant fractions of multiple-arm galaxies. However, if we consider the Hubble type and bar type together, grand design spirals are more frequent in early types than in late types for SA and SAB galaxies, while they are almost constant along the Hubble type for SB galaxies. There are clear correlations between spiral structures and the local background density: strongly barred, early-type, grand design spirals favor high-density regions, while non-barred, late-type, flocculent galaxies are likely to be found in low-density regions.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권4호
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• pp.288-305
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• 2000

A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects-the basics of yeast flocculation, the development of "new" flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer's yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous $\beta$-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculating bioreactors and discussing potential new uses of these systems.e systems.

• 한국미생물·생명공학회지
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• 제23권6호
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• pp.717-722
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• 1995

Using a flocculating Saccharomyes cerevisiae CA-1, an air-lift reactor equipped with a modified settler was used for ethanol fermentation. The effects of conditions such as aeration rate, initial glucose concentration, and dilution rate were studied using the air-lift reactor. In batch fermentation, optimum aeration rate was 0.5 vvm. In continuous fermentation, aeration rate and initial pH were fixed 0.5 vvm and 4.5, substrate concentration and dillution rate were changed 10-15% and 0.1-1.3. The maximum ethanol productivity was shown to be 20.4 g/l$\cdot $h in 10% glucose and 0.7 h$^{-1}$ dilution rate., and optimum operation condition considering the ethanol productivity and glucose utilization ratio was 0.5 h$^{-1}$ dilution rate in 10% glucose concentration.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.355-358
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• 2002

A sediments are Integral called as gravel, sand, clay, mineral materials which are settling in bottom layer of reservoir, stream, and oceans from land. In practical problems relations of sediments are flood by decreed of flow capacity and down of water quality. Dredged sediments are composed with constructed material and variety of pollutant compounds. Therefore, it is very much of cost effects in nationally, if development for use of constructed material separated only constructed material within sediments. And it will be continue to the dredge operation of stream sediment for retrofit of water environment and sustainable's after the years. The following results could be obtained : In case of high concentration sediments, sample for design of CDF was shown property of flocculent settling. Assuming that average inflow rate is 1, 000㎥/hr, mean residence time( $T_{d}$), average ponding depth( $H_{pd}$ ), and design surface area for flocculent settling( $A_{df}$ ) were 5 hr, 0.6m, and 15, 750 $m^2$ respectivelyrespectivelyy

• 대한환경공학회지
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• 제28권3호
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• pp.337-344
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• 2006

응집플록은 그 특성에 따라 분리막 오염에 지대한 영향을 미친다. 기존의 연구결과에서 보면, 자연입자에 의해 형성된 플록함유수는 인공입자에 의한 플록함유수에 비하여 낮은 투과량을 보이는 것으로 나타났다. 따라서 본 연구에서는 응집플록의 특성을 정량적으로 분석하고, 분리막 오염과의 상관성을 알아보고자 하였다. 이를 위해 응집 플록에 대한 image analysis, specific cake resistance 및 cake compressibility 등을 측정하였다. Image 분석은 플록의 fractal dimension을 구하는데 이용되었으며, dimension은 플록의 다공성, 크기나 표면의 거칠기를 표현하는데 유용하게 사용된다. 또한 케익 압축능은 플록이 쌓여 만들어진 막표면층의 특성을 분석하는데 사용되었다. 두 가지의 다른 특성을 가지는 플록으로서 자연입자를 핵으로 하는 응집플록과 카올린 입자를 핵으로 하는 응집플록을 선택하여 실험하였다. 실험결과에 따르면 자연입자와 인공입자에 의해 형성된 플록의 fractal dimension($D_2$) 값은 $1.79{\pm}0.07,\;1.84{\pm}0.06$을 각각 나타내었으며, 이것은 자연입자에 의해 형성된 플록이 인공입자에 의한 것 보다 더 다공성의 느슨한 형태로 존재하고 있다는 것을 나타내는 것이다. 자연입자에 의해 형성된 다공성의 느슨한 플록이 분리막 표면에서 케익층을 형성 할 때에는 상대적으로 쉽게 압축되어 케익비저항이 커지는 것을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제16권12호
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• pp.1874-1881
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• 2006

Flocculation of Candida tropicalis HY200 was systemically investigated to elucidate its mechanism, and used for cell cycles in repeated-batch cultivations for the production of xylitol from xylose. Flocculation occurred only after the late exponential phase of growth in the culture media and buffer within the narrow pH range of 3.0-5.0. The flocculation was completely inhibited by treatments of cells with proteases and partially reduced by treatments with carbohydrate-hydrolyzing enzymes and by the presence of mannose and glucose. The addition of calcium ions significantly enhanced the flocculation during cultivation, which was completely abolished by the addition of EDTA. The flocculent yeast HY200 provided repeated-batch cultivations employing cell recycles by flocculation over 6 rounds of cultivation for the production of xylitol from xylose, resulting in a relatively high productivity of averaged 4.6 g xylitol/l h over six batches and maximal 6.3 g xylitol/l h in the final sixth batch. Cell recycle by flocculation was fast and convenient, which could be applicable for the industrial scale of xylitol production.