• KSBB Journal
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• 제25권2호
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• pp.109-115
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• 2010

바이오 디젤은 석유 기반의 액체 연료를 대체할 수 있는 재생 가능한 대체 에너지로서, 특히 수송 연료에 있어 경유를 대신하여 일부 사용되어 있고 수요는 계속 증가할 것으로 보인다. 앞서 살펴본 바대로, 미세 조류의 지질을 바이오 디젤의 원료로 사용하는 방안은 기술적으로는 이미 실현 가능하다. 모든 생산 과정을 최적화시키고 biorefinery 개념을 도입하여 경제성을 최대한 끌어 올리며, 광생물반응기를 좀 더 개선시켜 효율을 높임과 동시에 수요 증가에 의해 가격이 낮아지게 되면 미세 조류를 이용한 바이오 디젤 생산의 경제적 문제를 해결할 수 있을 것이다. 특히 미세 조류에서의 유전공학적, 대사공학적인 지질 합성에 관한 연구는 아직도 몇 가지 유전자를 조작해보는 초기단계에 있고 이에 대한 발전 가능성은 긍정적이므로 앞으로 많은 연구자들이 이 분야에 관심을 가진다면 미세 조류 바이오 디젤의 실용화는 한 단계 앞당겨지리라 기대한다.

• 한국재료학회지
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• 제28권7호
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• pp.376-380
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• 2018

Microalgae produce not only lipids for biodiesel production but also valuable biochemicals which are often accumulated under cellular stress mediated by certain chemicals. While the microcarriers for the application of drug delivery systems for animal cells are widely studied, their applications into microalgal research or biorefinery are rarely investigated. Here we develope dual-functional magnetic microcapsules which work not only as flocculants for microalgal harvesting but also potentially as microcarriers for the controlled release of target chemicals stimulating microalgae to enhance the accumulation of valuable chemicals. Magnetic microcapsules are synthesized by layer-by-layer(LbL) coating of PSS-PDDA on $Fe_3O_4$ nanoparticle-embedded $CaCO_3$ microparticles followed by removing $CaCO_3$ sacrificial templates. The positively charged magnetic microcapsules flocculate microalgae by electrostatic interaction which are sequentially collected by the magnetophoretic separation. The microcapsules with a polycationic outer layer provide efficient binding sites for negatively charged microalgae and by that means are further utilized as a chemical-delivery and flocculation system for microalgal research and biorefineries.

• 한국해양바이오학회지
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• 제8권1호
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• pp.1-9
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• 2016

The hydrolysis of biomass to fermentable sugar (saccharification) and to oligosaccharide is an essential process in biotechnology including biorefinery and biofood. Various macroalgae are commercially cultivated in several Asian countries as a useful resource for food and agar production. Agar is a major component of the cell walls of red algae that can be hydrolyzed by agarase. Agarases are classified into ${\alpha}$-agarase (E.C. 3.2.1.158) and ${\beta}$-agarase (E.C. 3.2.1.81) according to the cleavage pattern and grouped in the glycoside hydrolase (GH) family (GH-16, GH-58, GH-86, GH-96, and GH-118) based on the amino acid sequences of the proteins. Agarases have been isolated from various bacteria found in seawater and marine sediments. To increase productivity of the enzyme, a research on recombinant enzymes has been done. The application of recombinant agarase can be possible in the various filed such as energy, food, cosmetics, medical and so on. This paper reviews the source, biochemical characteristics and production system of recombinant agarases for further study.

• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2413-2420
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• 2018

Sida acuta, a common type of weed in Thailand, contains relatively high cellulose (42.7%) content. We pretreated NaOH to improve glucose recovery from S. acuta. The effect of pretreatment temperature and NaOH concentration was fundamentally investigated based on hydrolysis efficiency with recovery of solid fraction. The pretreatment condition was determined to be 3% NaOH at $60^{\circ}C$ for 9 h, which showed the highest glucose recovery. The hydrolysates obtained by enzymatic hydrolysis of S. acuta were applied to the fermentation of Saccharomyces cerevisiae K35, and a theoretical yield of 97.6% was achieved at 18 h. This indicated that the hydrolysates medium without detoxification had no negative effects on the fermentation. The production of biomass into bioethanol was evaluated based on the material balance of 1,000 g basis. Following this estimation, approximately 28 g and 110 g bioethanol could be produced by untreated and pretreated S. acuta, respectively, and this production was improved about 3.9-fold by NaOH pretreatment. These results again show the importance of pretreatment in biorefinery process.

• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.442-450
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• 2019

Despite its potential as a renewable source for fuels and chemicals, lignin valorization still faces technical challenges in many aspects. Overcoming such challenges associated with the chemical recalcitrance of lignin can provide many opportunities to innovate existing and emerging biorefineries. In this work, we leveraged a biomass genetic engineering technology to produce phenolic aldehyde-rich lignin structure via downregulation of cinnamyl alcohol dehydrogenase (CAD). The structurally altered lignin obtained from the Arabidopsis thaliana CAD mutant was pyrolyzed to understand the effect of structural alteration on thermal behavior of lignin. The pyrolysis was conducted at 400 and $500^{\circ}C$ using an analytical pyrolyzer connected with GC/MS and the products were systematically analyzed. The results indicate that aldehyde-rich lignin undergoes fragmentation reaction during pyrolysis forming a considerable amount of C6 units. Also, it was speculated that highly reactive phenolic aldehydes facilitate secondary repolymerization reaction as described by the lower yield of overall phenolic compounds compared to wild type (WT) lignin. Quantum mechanical calculation clearly shows the higher electrophilicity of transgenic lignin than that of WT, which could promote both fragmentation and recondensation reactions. This work provides mechanistic insights toward biomass genetic engineering and its application to the pyrolysis allowing to establish sustainable biorefinery in the future.

• Journal of Microbiology and Biotechnology
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• 제32권11호
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• pp.1479-1484
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• 2022

Bacterial cellulose (BC) is gaining attention as a carbon-neutral alternative to plant cellulose, and as a means to prevent deforestation and achieve a carbon-neutral society. However, the high cost of fermentation media for BC production is a barrier to its industrialization. In this study, chestnut shell (CS) hydrolysates were used as a carbon source for the BC-producing bacteria strain, Gluconacetobacter xylinus ATCC 53524. To evaluate the suitability of the CS hydrolysates, major inhibitors in the hydrolysates were analyzed, and BC production was profiled during fermentation. CS hydrolysates (40 g glucose/l) contained 1.9 g/l acetic acid when applied directly to the main medium. As a result, the BC concentration at 96 h using the control group and CS hydrolysates was 12.5 g/l and 16.7 g/l, respectively (1.3-fold improved). In addition, the surface morphology of BC derived from CS hydrolysates revealed more densely packed nanofibrils than the control group. In the microbial BC production using CS, the hydrolysate had no inhibitory effect during fermentation, suggesting it is a suitable feedstock for a sustainable and eco-friendly biorefinery. To the best of our knowledge, this is the first study to valorize CS by utilizing it in BC production.

• Korean Membrane Journal
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• 제9권1호
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• pp.43-51
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• 2007

This paper describes the preparation and characterization of two kinds of fluorinated polybenzimidazole (PBI)s which can be potentially used for phosphoric acid-doped, high-temperature polymer electrolyte membrane fuel cells. Two kinds of perfluorocyclobutane (PFCB)-containing monomers were prepared via following synthetic steps; after fluoroalkylation of methyl 3-(hydroxy) benzoate and methyl 4-(hydroxy) benzoate with 1,2-dibromotetrafluoroethane and subsequent Zn-mediated dehalogenation, these compounds were cyclodimerized at $200^{\circ}C$ affording the ester-terminated monomers containing PFCB ether groups. The synthesized intermediates and monomers were characterized using FT-IR, $^1H-NMR,\;^{19}F-NMR$, and mass spectroscopy. The fluorinated PBIs were then successfully prepared through the solution polycondensation of the monomers and 3,3'-diaminobenzidine in polyphosphoric acid. Compared with traditional PBI, the glass transition temperatures of the fluorinated PBIs were obtained at $262^{\circ}C\;and\;269^{\circ}C$ which are lower than that of PBI and their initial degradation temperatures were still high over $400^{\circ}C$ under nitrogen. The fluorinated PBIs showed higher d-spacing values and improved solubility in several organic solvents as well as phosphoric acid, which confirmed they could be good candidates for the high temperature fuel cell membranes.

• 멤브레인
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• 제17권3호
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• pp.184-190
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• 2007

본 연구는 불소계 폴리실록산이미드 공중합체 막을 이용하여 휘발성 유기 화합물(Volatile Organic Compounds; VOCs)의 일종인 dichloromethane(DCM)을 물로부터 투과증발 분리하는 것을 목적으로 한다. 유연한 사슬을 갖는 diamine-terminated polydimethylsiloxane(SIDA)과 경직된 구조를 갖는 불소계 방향족 디아민 단량체(2-(perfluorohexyl)ethyl-3,5-diaminobenzene PFDAB)과 4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)를 이용하여 일련의 소수성 불소계 폴리실록산이미드 공중합체 막을 제조하여 다이아민의 구성성분에 따른 분리능의 변화를 상온에서 관찰하였다. 공중합체 막 내의 다이아민 성분 중 SIDA의 함량은 0, 25, 50, 75, 100 mol%로 조절되었으며, 원액의 조성은 DCM 0.05 wt%를 사용하였다. 소수성이 높고 자유부피가 큰 SIDA의 함량이 증가함에 따라 소수성 용매인 DCM의 수착도 및 수착선택도가 증가하는 경향을 나타내었으며, 확산계수 및 확산선택도 또한 증가하여 궁극적으로는 투과플럭스와 투과선택도가 증가하는 것을 확인할 수 있었다.

• BMB Reports
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• 제45권2호
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• pp.59-70
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• 2012

Carbon catabolite repression (CCR) is a key regulatory system found in most microorganisms that ensures preferential utilization of energy-efficient carbon sources. CCR helps microorganisms obtain a proper balance between their metabolic capacity and the maximum sugar uptake capability. It also constrains the deregulated utilization of a preferred cognate substrate, enabling microorganisms to survive and dominate in natural environments. On the other side of the same coin lies the tenacious bottleneck in microbial production of bioproducts that employs a combination of carbon sources in varied proportion, such as lignocellulose-derived sugar mixtures. Preferential sugar uptake combined with the transcriptional and/or enzymatic exclusion of less preferred sugars turns out one of the major barriers in increasing the yield and productivity of fermentation process. Accumulation of the unused substrate also complicates the downstream processes used to extract the desired product. To overcome this difficulty and to develop tailor-made strains for specific metabolic engineering goals, quantitative and systemic understanding of the molecular interaction map behind CCR is a prerequisite. Here we comparatively review the universal and strain-specific features of CCR circuitry and discuss the recent efforts in developing synthetic cell factories devoid of CCR particularly for lignocellulose-based biorefinery.