• 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.

• Food Science and Biotechnology
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• 제17권3호
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• pp.558-563
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• 2008

To prevent weakly flocculating characters of bottom brewing yeast during first fermentation, various technical investigations were carried out using strain of Saccharomyces cerevisiae. It appeared that the propagation at $10^{\circ}C$ promoted the molecular structure and biochemical composition of cell wall in favor of flocculation. The yeast grown at $20^{\circ}C$ by addition of zinc ion also had a stimulating effect on flocculation behavior during first fermentation cycle. The zinc ion did not influence directly on the changes of cell wall in favor of stronger flocculence. The increased fermentation activity of yeast due to addition zinc ion was rather responsible for the intensified flocculation capacity. It was concluded that the weakly flocculating characters of bottom brewing yeast during first fermentation can be solved by using yeast propagated at $10^{\circ}C$ or by means of yeast by addition of zinc ion during propagation.

• KSBB Journal
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• 제4권1호
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• pp.11-14
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• 1989

Tower fermentor를 이용한 연속 알콜발효에서 cell re-cycle과 aeration에 대한 영향을 검토하였다. 균주는 floc-culationg 효모인 Saccharomyces cerecisiae TS4를 를 사용하였다. 15% glucose를 사용한 cell recycle system의 연속 알콜발효에서 cell 농도는 50%/1였고, ethanol productiv는 26.4g EtOH/l-hr로서 cell농도가 가장 높은 값을 나타내었으며, aeration rate는 3.8$\times$ $10^-^3$ VVM이상부터는 ethanol pro-ductivity가 감소하였다.

• 한국미생물·생명공학회지
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• 제19권5호
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• pp.487-490
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• 1991

효모 재순환계에 의한 당밀의 연속발효를 하였다. 단계적으로 YPD배지 농도를 10g/l에서 183.5g/l로 증가시킨 후 최종 발효배지는 당밀로 하였다. 최고의 효모농도는 25g/l였고, 운전중 평균 효모농도는 23.5g/l으로 종래 회분식보다 3.4배 높았다. 최적 발효조건은 180g/l의 당밀배지를 공급하였을 때 교반속도 500rpm, 희석을 0.037$h^{-1}$였다. 이 조건을 645시간 연속 운전하였으며 최고 알코올 생산성은 4.9g$l\cdot h$로서 이때의 희석율은 0.091$h^{-1}$, 알코올 농도는 53.9g/l이었다.

• 한국미생물·생명공학회지
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• 제24권6호
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• pp.699-704
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• 1996

About 600 microorganisms isolated from soil, marsh, compost, etc. were examined for their flocculating ability in the kaolin suspension and swine wastewater. Among them, K-199 was the best producer of flocculant and was identified to be a species belong to the genus Corynebacterium. The maximum production of the flocculant from Corynebacterium sp. K-199 was observed in culture medium containing 2% glycerol, 0.4% peptone, 0.3% K$_{2}$HPO$_{4}$, 0.1% CaCO$_{3}$, 0.05% NaCl, 0.1% yeast extract, 0.1% MgSO$_{4}$,7H$_{2}$O and initial pH 7.5 when cultured with rotary shaker controlled at 25$\circ$C and 150 rpm. Under the optimal culture condition with jar fermentor, the maximum production was reached to flocculating activity of 780 units/ml after 4 days. From the results of the activity be fully maintained by periodate oxidization, it suggests that the activity is due to the protein.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권1호
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• pp.85-90
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• 2005

A downstream process was developed for the production of yeast extract from brewer's yeast cells. Various downstream processing conditions including clarification, debittering, and the Maillard reaction were considered in the development of the process. This simple and economic clarification process used flocculating agents, specifically calcium chloride ($1\%$). After the clarification step, a Maillard reaction is initiated as a flavor-enhancing step. By investigating the effects of several operation parameters, including the type of sugar added, sugar dosage, glycine addition, and temperature, on the degree of browning (DB), giucose addition and reaction temperature were found to have significant effects on DB. A synthetic adsorption resin (HP20) was used for the debittering process, which induced a compositional change of the hydrophobic amino acids in the yeast hydrolysate, thereby reducing the bitter taste. The overall dry matter yield and protein yield for the entire process, including the downstream process proposed for the production of brewer's yeast extract were 50 and $50\%$, respectively.

• 한국미생물·생명공학회지
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• 제23권6호
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• pp.723-729
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• 1995

A flocculating sugar tolerant yeast strain was isolated from fermenting Takju. This strain was identified as Saccharomyces cerevisiae CA-1 according to the Lodder's yeast taxonomic studies. The isolated yeast could grow in 50% glucose and in 7% ethanol in the YPD medium. It's optimal growth temperature, initial pH, shaking rate and initial glucose concentration for ethanol fermentation showed 35$\circ$C, 4.5, 150 rpm, 15%, respectively. Ethanol concentration was 63 g/l in 20% glucose after 24 hours, fermentation yield was 0.49 g-ethanol/g-glucose in 10% glucose after 24 hours and ethanol productivity was 3.09 g/l$\cdot $h in 10% glucose after 12 hours in batch fermentation. Repeated batch fermentation was possible for over 50 days and ethanol yield, ethanol productivity and substrate conversion rate were 0.39-0.50 g/g, 1.63-2.08 g/l$\cdot $h and more than 99%, respectively during these periods.

• KSBB Journal
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• 제7권1호
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• pp.9-14
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• 1992

A cone type of tower fermentor loaded with flocculating Sacchromyces uvarum was used to study the fermentor performance. The performance of cone type fermentor was compared with those of other fermentors. The maximum yeast concentration in the cone type of tower fermentor was 35.9-43.0g/1.hr and the maximum ethanol productivity was 14.75g/1.hr at the dilution rate 0.26 $hr^{-1}$. The ethanol yield was 0.446-0.472g ETOH/g Glucose. It was concluded that a cone type of tower fermentor might offer better perspectives for continous etanol fermentation.

• 한국식품영양과학회지
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• 제24권5호
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• pp.790-795
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• 1995

응집제를 생산하는 미생물은 토양시료로 부터 분리하여 그 중 응집활성이 높은 1 균주를 선택하여 분류학적 위치를 조사한 결과, Arcuadendrop sp.으도 동정되었으며 본 균주를 Arcuadendron sp. TS-49로 명명하였다. 응집제 생산 최적배지는 3% glucose, 0.2% yeast extract, 0.1% $NH_4Cl$, 0.05% $MnSO_4$, 0.01% $MgSO_4$ (pH 7.0)의 경우가 가장 우수하였으며, 배양 온도 및 배양 pH는 $30^{\circ}C$, pH 7.0일 때가 최적이었다. 최적 배양조건하에서 4~5일간 배양시 응집제 생산량이 최대에 도달하였으며 배양 시간의 경과와 더불어 응집활성은 급격히 감소하는 현상을 보여 생분해성이 우수함을 나타내었따. 이때의 응집제 생산량은 screening 배지에 비해 거의 10배 정도로 향상되었으며, 각종 microorganism과 suspended solid에 대한 응집작용을 검토한 결과, 정도의 차이는 있으나 모든 공시물질에 응집활성을 나타내었다.응집제의 조성을 검토하기 위해 각종 정성 test를 행한 결과, 당과 단백질이 검출되어 일종의 glycoprotein 임이 확인되었다.

• Applied Biological Chemistry
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• 제41권6호
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• pp.465-470
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• 1998

미생물이 생산하는 유기폐수처리용 생물응집제를 개발하기 위하여 보관균주 및 자연계로부터 100 units/ml 이상의 응집활성을 나타내는 응집제 생산균주를 1차로 분리하고 돈분폐수에서 가장 높은 제거율을 보인 KH-54를 최종 선별하였다. 선별된 균주는 Aeromonas hydrophila로 동정되었으며 응집제 생산을 위한 최적 배양조건은 2.0% mannitol, 0.05% ammonium chloride, 0.02% $KH_2PO_4$, 0.01% $MgSO_4{\cdot}7H_2O$, 0.05% yeast extract 조성의 배지와 초기 pH 7.0, 배양온도 $25^{\circ}C$ 및 교반속도 150 rpm 의 환경인자들이었다. 상기의 조건으로 4일 배양하였을 때 770 units/ml의 응집활성과 81%의 높은 nephelometer turbidity unit(NTU) 제거율을 나타내었으며 이 응집물질은 돈분폐수 이외 두부공업폐수 92%, 제당폐수 78%, 주정공업폐수 68% 및 항생물질 발효공업폐수 36%의 NTU 제거율을 각각 나타내었다.