• 유기물자원화
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• 제24권2호
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• pp.51-58
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• 2016

일체형 2상 혐기성소화 방식은 기존 분리형 2상 혐기성소화의 단점을 보완할 수 있는 기술로 산발효조와 메탄발효조가 병합된 형태의 일체형으로 구성되어 유기물 부하변동 대처 용이, 설치부지면적 감소 등의 이점이 있다. 본 연구는 음폐수를 기질로 일체형 2상 혐기성소화의 유기물 분해효율 및 바이오가스 생산량 등에 대한 실험을 실시하여 기존 분리형 2상 혐기성소화와의 효율 비교를 통해 대규모 플랜트 설치의 타당성 여부를 검토하였다. 5ton/일 규모의 Pilot Plant를 구성하여 약 130일 간 소화조 내 유기물 변화, 바이오가스 생산량 및 메탄함량 등의 실험을 실시하였다. 실험 결과, 평균 음폐수 투입량은 $4.1m^3$/일이었으며, 이때 VS 제거효율은 약 77%로 나타났다. 바이오가스는 평균적으로 투입 음폐수 ton당 약 $63.0m^3$($0.724m^3/kg-VS_{added}$)가 발생되었으며, 메탄함량은 약 61.3%로 분석되었다. 일체형 2상 혐기성소화는 기존 산발효조와 메탄발효조가 분리된 소화방식과 유기물 제거 측면에서 다소 높게 나타났다. 결과적으로 일체형 2상 혐기성소화 방식은 충분히 고농도 유기성 폐수인 음폐수 처리에 있어서 상용화가 가능하다는 결론을 내릴 수 있었다.

• 청정기술
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• 제20권4호
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• pp.349-353
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• 2014

숙신산은 의약품, 식품 첨가물, 청정용매와 같은 종래의 응용 이외에도 생분해성 고분자의 중요한 전구물질로 주목 받고 있다. 그러나 최근 화석 연료의 높은 가격과 화석 원료 유래 제품의 전주기에 걸친 온실가스 배출로 인해 재생 가능한 바이오매스에 의한 숙신산의 생물학적 생산에 대한 관심이 높아지고 있다. 본 연구에서는 숙신산의 선택적인 추출과 농축을 동시에 수행할 수 있는 공정으로서 이미다졸계 이온성 액체/$K_2HPO_4$에 의한 수상이성분계를 적용하였다. 실험 결과 숙신산에 존재하는 $K_2HPO_4$ 수용액에 적정량의 이미다졸계 이온성 액체가 첨가됨에 따라 안정한 수상이성분계가 형성됨을 확인할 수 있었으며 수상이성분계 형성 능력은 [HMIm][Br]${\fallingdotseq}$[OMIm][Br]>[BMIm][Br]>[EMImBr]의 순서로 나타났다. 숙신산의 최대 추출 효율은 약 90%였으며 이온성 액체에서 양이온 사슬길이가 증가할수록 상부상으로 동반 추출되는 물의 양이 줄어들어 숙신산의 선택적 농축효과가 크게 나타났다. 따라서 본 연구에서 사용된 이미다졸계 이온성 액체와 $K_2HPO_4$으로 구성된 수상이성분계는 숙신산의 선택적 추출과 농축에 효과적임을 알 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제9권2호
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• pp.179-183
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• 1999

A recombinant form of hirudin, a potent thrombin-specific inhibitor derived from the bloodsucking leech, was expressed as a secretory product in Saccharomyces cerevisiae under the control of GALl0 promoter and the mating factor $\alpha$pre-pro leader sequence. In an attempt to produce recombinant hirudin (r-Hir) of therapeutic purity in large quantities, the fed-batch fermentation was carried out by using this recombinant yeast, and subsequently downstream processing was developed with the preparative-scale column chromatography systems. About 234 mg/l of biologically active r-Hir was produced as a secretory product by the fed-batch fermentation strategy developed for an efficient downstream processing. Using a two-step chromatography process (an anion exchange chromatography followed by the reverse phase HPLC), the r-Hir was purified to>98% with an overall recovery yield of 84%. According to the N-terminal amino acid sequencing, the purified r-Hir was found to have the predicted N-terminal amino acid sequence. The biological activity of the purified r-Hir to inhibit thrombin was also identical to that of the commercial hirudin.

• Journal of Microbiology and Biotechnology
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• 제16권1호
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• pp.68-76
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• 2006

Despites many attempts to explore the microbial diversity in kimchi fermentation, the predominant flora remains controversial to date. In the present study, major lactic acid bacteria (LAB) were investigated in Chinese cabbage kimchi in the early phase of fermention. For the samples over pH 4.0, viable cell counts of Leuconostoc and Pediococcus were $10^6\;cfu/ml$ and below $10^2\;cfu/ml$, respectively, and 20 isolates out of 172 were subjected to a biochemical identification (API 50 CH kit) as well as molecular-typing methods including ITSPCR with a RsaI digestion and 16s rRNA gene sequence analysis for species confirmation. Seven isolates were nicely assigned to Lb. brevis, 6 to Leuconostoc spp. (2 mesenteroides, 2 citreum, I carnosum, I gasicomitatum), 4 to Weissella (3 kimchii/cibaria, 1 hanii) and 2 to other Lactobacillus spp. (1 farciminis, 1 plantarum). On the other hand, the biochemical identification data revealed 9 strains of Lb. brevis, 6 strains of Leuconostocs,2 strains of Lb. plantarum and 1 strain each of Lb. coprophilus and Lactococcus lactis. However, a single isolates, YSM 16, was not matched to the ITS-PCR database constructed in the present study. Two Lb. brevis strains by API 50 CH kit were reassigned to W kimchii/cibaria, Lb. coprophilus or W hanii, respectively, judging from the results by the above molecular typing approaches. As a whole, the identification data obtained by the biochemical test were different from those of ITS-PCR molecular method by about $63\%$ at genus-level and $42\%$ at species-level. The data by the ITS-PCR method conclusively suggest that predominant LAB species is probably heterolactic Lb. brevis, followed by W kimchii/cibaria, Leuc. mesenteroides, and Leuc. citreum, in contrast to the previous reports [3] that Leuc. mesenteroides is the only a predominant species in the early phase kimchi fermentation.

• 한국식품과학회지
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• 제34권6호
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• pp.1085-1090
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• 2002

Dextransucrase의 수용체반응(acceptor reaction)을 이용하여 판노스(panose)를 포함한 다양한 당전이화합물을 발효식품에서 생성하기 위하여 고활성 dextransucrase를 저온에서 생성하는 Leuconostoc속 균주를 동치미김치로부터 분리 및 선발하였다. 동치미를 제조하여 $8^{\circ}C$에서 발효시키면서 분리한 Leuconostoc속 균주중에서 균체의 증식유도기간(lag phase), 최대균체량(g/L), 균체의 비성장속도$(\mu)$ 및 dextransucrase 활성을 종합적으로 비교하여 우수균주를 선발하였고, 최종적으로 MIDI를 이용하여 Leuc. mesenteroides로 동정하였다. 본 균주는 김치를 포함한 저온성 발효식품에서 당전이화합물을 생성하여 기능성을 부여하는 스타터로 사용될 수 있을 것으로 판단된다.

• 한국식품과학회지
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• 제51권4호
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• pp.324-329
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• 2019

무 발효물의 발효기간에 따른 휘발성 향기성분을 SPME를 이용하여 추출하고 GC-MS로 분석하였다. 총 46종의 휘발성 향기 성분이 검출되었으며, 이들 중 함황화합물의 함량이 가장 높았다. 발효 전(발효 0일차) 휘발성 향기성분의 조성 비율을 보면 함황화합물(95.85%)과 알데하이드(2.61%)가 대부분을 차지했고, 발효 후(발효 2일차) 휘발성 향기성분의 조성 비율은 함황화합물(75.53%), 산(11.12%), 알코올(8.44%) 및 알데하이드(1.48%)으로 구성되어 변화가 큼을 알 수 있었다. 발효 후 함황화합물의 총 함량은 18,074.7 ng/g에서 2,996.2 ng/g으로 가장 크게 감소하였고, 이 성분 중 원재료의 주 성분으로 알려져 있는 dimethyl disulfide, dimethyl trisulfide, diallyl sulfide, diallyl disulfide와 diallyl trisulfide의 함량이 발효 기간이 증가함에 따라 크게 감소하는 경향을 보였다. 또한 이 성분들은 자극적인 함황화합물 특유의 마늘향과 파향을 나타내는 휘발성 화합물로 발효 후 함량이 크게 감소하여 무 발효물의 발효 전후 향미특성에 크게 영향을 줄 것으로 생각된다. 반면 acetic acid는 발효 전 0 ng/g에서 발효 후 441.0 ng/g으로 크게 증가하였고, 알코올은 41.1 ng/g에서 334.9 ng/g으로 발효 기간이 경과함에 따라 크게 증가하는 것을 확인할 수 있었다. 발효 2일차에 증가된 acetic acid (441.0 ng/g)와 1-hexanol (139.3 ng/g)은 각각 톡 쏘는 신향, 과일향과 알코올향을 나타내 발효 전후 무 발효물의 향미특성에 영향을 미칠 것으로 생각된다.

• Journal of Microbiology and Biotechnology
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• 제16권11호
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• pp.1690-1698
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• 2006

In order to investigate the effect of dissolved oxygen (DO) level on AVM $B_{1a}$ production by a high yielding mutant of Streptomyces avermitilis, five sets of bioreactor cultures were performed under variously controlled DO levels. Using an online computer control system, the agitation speed and aeration rate were automatically controlled in an adaptive manner, responding timely to the oxygen requirement of the producer microorganism. In the two cultures of DO limitation, the onset of AVM $B_{1a}$ biosynthesis was observed to casually coincide with the fermentation time when oxygen-limited conditions were overcome by the producing microorganism. In contrast, this phenomenon did not occur in the parallel fermentations with DO levels controlled at around 30% and 40% throughout the entire fermentation period, showing an almost growth-associated mode of AVM $B_{1a}$ production: AVM $B_{1a}$ biosynthesis under the environments of high DO levels started much earlier than the corresponding oxygen-limited cultures, leading to a significant enhancement of AVM $B_{1a}$ production during the exponential stage. Consequently, approximately 6-fold and 9-fold increases in the final AVM $B_{1a}$ production were obtained in 30% and 40% DO-controlled fermentations, respectively, especially when compared with the culture of severe DO limitation (the culture with 0% DO level during the exponential phase). The production yield ($Y_{p/x}$), volumetric production rate (Qp), and specific production rate (${\bar{q}}_p$) of the 40% DO-controlled culture were observed to be 14%, 15%, and 15% higher, respectively, than those of the parallel cultures that were performed under an excessive agitation speed (350 rpm) and aeration rate (1 vvm) to maintain sufficiently high DO levels throughout the entire fermentation period. These results suggest that high shear damage of the high-yielding strain due to an excessive agitation speed is the primary reason for the reduction of the AVM $B_{1a}$ biosynthetic capability of the producer. As for the cell growth, exponential growth patterns during the initial 3 days were observed in the fermentations of sufficient DO levels, whereas almost linear patterns of cell growth were observed in the other two cultures of DO limitation during the identical period, resulting in apparently lower amounts of DCW. These results led us to conclude that maintenance of optimum DO levels, but not too high to cause potential shear damage on the producer, was crucial not only for the cell growth, but also for the enhanced production of AVM $B_{1a}$ by the filamentous mycelial cells of Streptomyces avermitilis.

• 한국미생물·생명공학회지
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• 제14권6호
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• pp.473-478
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• 1986

미생물에 의한 천연유지의 분해자화과정을 극명함으로써 값싼 유지를 발효원으로서 착용하기 위하여 팜유자화성 유용균주인 Torulopsis candida Y-128과 Acinetobacter calcoaceticus KB-2가 생산하는 리파제의 특성과 이들 균주의 생리적인 특성을 검토하였다. T. candida Y-128은 팜유입자에 부착·자화하며 리파제의 작용에 의해 유리되는 분포화지방산을 포화지방산에 비해 쉽게 자화이용 함으로써 균체증식이 이루어지고 있었다. T. candida Y-128의 리파제는 대부분 균체내에 존재하는데 비해, A calcoaceticus KB-2는 배양시에 균체증식 대수기부터 균체외로 리파제가 생성됨을 알수 있었으며, 리파제에 의해 유리된 포화 지방산도 다른 균주에 비해 자화이용이 용이함을 알 수 있었다. 두 균주는 배양액중에 리파제를 축적하지 않고 균체생육에 필요한 정도를 생산하며 천연중지중 1(3-)-위치의 지방산에 작용하는 위치특이성을 나타내었다. 따라서 두 균주는 천연유지입자에 부착하여 1(3-)- 위치의 지방산을 분해하고, 분해생성물은 지방산대사경로를 거쳐 자화이용되는 것으로 보여진다.

• 상하수도학회지
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• 제20권3호
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• pp.397-402
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• 2006

The treatment characteristics of leachate produced from pretreatment facilities like composting and feeding were investigated in a mesophilic anaerobic treatment. Experiments were performed in two phase which were acidification and methane fermentation. The acidification step was optimized for OLR from 1 to $4.5kg\;COD/kg\;VS{\cdot}day$ without adding NaOH. As experiment dates became longer, the solubilization ratio of particles increased up to 30% over 70 days. TVA was generated up to maximum 9,970mg HAc/L at OLR of $2kg\;COD/kg\;VS{\cdot}day$. But TVA was generated to minimum 6,519mg HAc/L at OLR of $4.5kg\;COD/kg\;VS{\cdot}day$. The acidification ratio was analyzed from 10.9% to 3.8% at OLR of $2kg\;COD/kg\;VS{\cdot}day$ and $4.5kg\;COD/kg\;VS{\cdot}day$ respectively. After 55 days, salt contents in the acid fermenter were accumulated and stabilized at the concentration of 3,150mg/L. Sodium ion($Na^+$) concentration was stabilized at 1,300mg/L. At methane fermentation step, biogas was generated up to 750ml and 937.5ml at the feeding volume of 20ml and 25ml respectively for acid fermented liquid during 25 days. About 80% of total biogas was generated during early 15 days and 95% were generated during 18 days respectively. After 25 days of the BMP test, acetic acid was removed approximately 97% and 98%, in case of those two experimental conditions.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.465-469
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• 2006

Two mesophilic trickling bed bioreactors filled with two different types of media, hydrophilic- and hydrophobic-cubes, were designed and tested for hydrogen production via anaerobic fermentation of sucrose. Each reactor consisted of a column packed with polymeric cubes and inoculated with heat-treated sludge obtained from anaerobic digestion tank. A defined medium containing sucrose was fed with changing flow rate into the capped reactor, hydraulic retention time and recycle rate. Hydrogen concentrations in gas-phase were constant, averaging 40% for all conditions tested. Hydrogen production rates increased up to $10.5 L{\cdot};h^{-1}{\cdot}L^{-1}$ of reactor when influent sucrose concentrations and recycle rates were varied. Hydrophobic media provided higher value of hydrogen production rate than hydrophilic media at the same operation conditions. No methane was detected when the reactor was under a normal operation. The major fermentation by-products in the liquid effluent of the both trickling biofilters were acetate and butyrate. The reactor filled with hydrophilic media became clogged with biomass and bio gas, requiring manual cleaning of the system, while no clogging occurred in the reactor with hydrophobic media. In order to make long-term operation of the reactor filled with hydrophilic media feasible, biofilm accumulation inside the media in the reactor with hydrophilic media and biogas produced from the reactor will need to be controlled through some process such as periodical backwashing or gas-purging. These tests using trickling bed biofilter with hydrophobic media demonstrate the feasibility of the process to produce hydrogen gas in a trickle-bed type of reactor. A likely application of this reactor technology could be hydrogen gas recovery from pre-treatment of high carbohydrate-containing wastewaters.