• Journal of Microbiology and Biotechnology
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• 제26권7호
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• pp.1290-1302
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• 2016

Microalgae are being researched for their potential as attractive biofuel feedstock, particularly for their lipid production. For maximizing biofuel production, it is necessary to explore the effects of environmental factors on algal lipid-producing potential. In this study, the effects of nitrogen (N) sources (NO₂-N, NO₃-N, urea-N, NH₄-N, and N-deficiency) and carbon-to-nitrogen ratios (C/N= 0, 1.0, 3.0, and 5.0) on algal lipid-producing potential of Chlorella sp. HQ were investigated. The results showed that for Chlorella growth and lipid accumulation potential, NO₂-N was the best amongst the nitrogen sources, and NO₃-N and urea-N also contributed to algal growth and lipid accumulation potential, but NH₄-N and N-deficiency instead caused inhibitory effects. Moreover, the results indicated that algal lipid-producing potential was related to C/N ratios. With NO₂-N treatment and carbon addition (C/N = 1.0, 3.0, and 5.0), total lipid yield was enhanced by 12.96-20.37%, but triacylglycerol (TAG) yields decreased by 25.52-94.31%. As for NO₃-N treatment, carbon addition led to a 17.82-57.43%/25.86-82.67% reduction of total lipid/TAG yields. When NH₄-N was used as the nitrogen source, total lipid/TAG yields were increased by 46.67-113.33%/28.99-74.76% with carbon addition. The total lipid/TAG yields of urea-N treatment varied with C/N ratios. Overall, the highest TAG yield (TAG yield: 38.75 ± 5.21 mg/l; TAG content: 44.16 ± 4.35%) was achieved under NO₂-N treatment without carbon addition (C/N = 0), the condition that had merit for biofuel production.

• 청정기술
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• 제23권4호
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• pp.435-440
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• 2017

바이오 연료 생산을 위한 3세대 바이오매스, 즉 미세조류 및 거대조류의 급속 열분해는 최근 1 세대 및 2 세대 바이오매스와 비교하여 실험적으로 연구된 바 있다. 하지만 거대조류의 경우 스케일업을 위한 공정모사 및 공정설계 연구는 거의 전무한 실정이다. 이 연구에서는 갈조류 급속 열분해의 벤치 스케일 실험 데이터에 근거하여 갈조류로부터 최종적으로 디젤을 생산하는 산업 규모의 공정을 상용 공정모사기를 이용하여 설계하고 모사하였다. 이때 육상 바이오매스 대비 갈조류의 조성 차이를 수용하기 위해 공정 설계에 특별한 주의를 기울였다. 연간 380,000톤의 건조 갈조류 원료를 바이오 디젤로 전환하는 전체 공정을 경제적으로 평가하고 최소 (디젤) 판매 가격 또한 산정하였다.

• 공업화학
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• 제24권3호
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• pp.285-290
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• 2013

최근 비식용 바이오매스 자원인 미세조류를 이용하여 배가스 내의 이산화탄소를 저감함과 동시에 바이오연료를 생산하는 공정이 개발되고 있다. 미세조류 바이오연료 전환 공정은 미세조류 경작, 수확, 추출, 전환 등의 다양한 공정들이 연속적으로 이용된다. 이에 따라 실제 에너지 생산 효과에 대한 우려가 여전히 존재한다. 본 연구는 석탄 발전소에서 배출되는 배가스를 이용하여 파일럿 광생물 반응기에서 생산되는 미세조류를 대상으로 바이오연료 전환에 따른 실에너지 효율을 계산하였다. 에너지 전환 공정은 전이에스터화, 열분해 공정을 선정하였으며 미세조류의 지질 함량에 따른 영향을 검토하였다. 미세조류 바이오연료 전환 공정들은 경작, 수확, 추출, 전환 등에 소요되는 에너지보다 많은 양의 에너지를 가지는 바이오연료를 생산할 수 있으며 지질 함량이 높은 미세조류는 열분해보다 전이 에스터화 반응이 효과적이었다.

• 한국응용과학기술학회지
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• 제35권2호
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• pp.540-559
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• 2018

액상 바이오연료를 생산할 수 있는 하수슬러지는 자국의 에너지 안보와 지속가능한 생산이 가능하고 경제적인 원료로 여겨지고 있다. 열화학적 기술은 하수슬러지를 에너지화, 연료화할 수 있는 가장 효과적인 방법이다. 일반적으로 하수슬러지는 수분 함량이 80% 이상으로 높은 금속 함량과 14 ~ 20 MJ/kg의 발열량을 갖고 있다. 본 논문에서는 하수슬러지를 활용한 액상 바이오연료를 생산하는 열분해 반응, 전이에스테르화 반응, 초임계 반응 기술에 대해 살펴보고자 한다. 또한, 하수슬러지 유래 액상 바이오연료의 연료적 특성과 액상 바이오연료와 관련한 국내 법에 대해 검토하였다.

• Journal of Microbiology and Biotechnology
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• 제29권6호
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• pp.952-961
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• 2019

Chlorella spp. are green algae that are found across wide-ranging habitats from deserts to arctic regions, with various strains having adapted to survive under diverse environmental conditions. In this study, two novel Chlorella strains (ABC-002, ABC-008) were isolated from a freshwater lake in South Korea during the winter season and examined for possible use in the biofuel production process. The comparison of ABC-002 and ABC-008 strains with Chlorella vulgaris UTEX265 under two different temperatures ($10^{\circ}C$, $25^{\circ}C$) revealed their cold-tolerant phenotypes as well as high biomass yields. The maximum quantum yields of UTEX25, ABC-002, and ABC-008 at $10^{\circ}C$ were 0.5594, 0.6747, and 0.7150, respectively, providing evidence of the relatively higher cold-resistance capabilities of these two strains. Furthermore, both the biomass yields and lipid content of the two novel strains were found to be higher than those of UTEX265; the overall lipid productivities of ABC-002 and ABC-008 were 1.7 ~ 2.8 fold and 1.6 ~ 4.2 fold higher compared to that of UTEX265, respectively. Thus, the high biomass and lipid productivity over a wide range of temperatures indicate that C. vulgaris ABC-002 and ABC-008 are promising candidates for applications in biofuel productions via outdoor biomass cultivation.

• 기술혁신연구
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• 제28권3호
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• pp.29-53
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• 2020

기존 주경로 연구는 과거 핵심기술의 진화를 구조화하는데 적합하나, 패러다임 전환기의 잠재적 후보기술 파악과 주류기술 교체를 예측하기는 어렵다. 본 연구는 링크 중요도, 성장 속도 지표, 핵심 루트 방법을 복합해 특허 인용 네트워크로부터 주경로상의 기술을 대체할 잠재적 후보기술들을 파악하는 방법을 제시한다. 링크 중요도에 기반해 주경로를 도출하고, 성장 속도 지표를 활용해 주경로 대비 고성장하는 잠재적 후보기술 경로들을 도출한다. 성장 속도 지표는 상대적 성장성 평가에 활용되고, 이를 통해 주경로를 교체할 가능성이 높은 잠재적 후보기술을 파악할 수 있다. 차세대 기술 후보들이 다수 등장해 경쟁하고 있는 바이오 연료기술에 적용한 결과 실제 차년도에 주경로상의 기술을 교체하는 후보기술들을 파악할 수 있었다. 기술 패러다임 전환기 후보기술에 대한 정량적 분석을 가능하게 하고, 주경로 기법의 활용범위를 미래기술 예측으로 확대한 측면에서 학문적 의의가 있다. 실무에서는 차세대 후보기술 파악의 정확도 제고에 기여할 수 있다.

• Journal of Microbiology and Biotechnology
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• 제28권4호
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• pp.571-578
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• 2018

Biofuel production using lignocellulosic biomass is gaining attention because it can be substituted for fossil fuels without competing with edible resources. However, because Saccharomyces cerevisiae does not have a ${\text\tiny{D}}$-xylose metabolic pathway, oxidoreductase or isomerase pathways must be introduced to utilize ${\text\tiny{D}}$-xylose from lignocellulosic biomass in S. cerevisiae. To elucidate the biochemical properties of xylose isomerase (XI) from Piromyces sp. E2 (PsXI), we determine its crystal structure in complex with substrate mimic glycerol. An amino-acid sequence comparison with other reported XIs and relative activity measurements using five kinds of divalent metal ions confirmed that PsXI belongs to class II XIs. Moreover kinetic analysis of PsXI was also performed using $Mn^{2+}$, the preferred divalent metal ion for PsXI. In addition, the substrate-binding mode of PsXI could be predicted with the substrate mimic glycerol bound to the active site. These studies may provide structural information to enhance ${\text\tiny{D}}$-xylose utilization for biofuel production.

• Journal of Microbiology and Biotechnology
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• 제22권11호
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• pp.1471-1477
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• 2012

Carotenoids produced by non-photosynthetic bacteria protect organisms against lethal photodynamic reactions and scavenge oxygenic radicals. However, the carotenoid produced by Gordonia alkanivorans SKF120101 is coupled to reducing power generation. SKF120101 selectively produces carotenoid under light conditions. The growth yield of SKF120101 cultivated under light conditions was higher than that under dark condition. In the cyclic voltammetry, both upper and lower voltammograms for neutral red (NR) immobilized in intact cells of SKF120101 were not shifted in the condition without external redox sources but were commonly shifted downward by glucose addition and light. Electric current generation in a biofuel cell system (BFCS) catalyzed by harvested cells of SKF120101 was higher under light than dark condition. The ratio of electricity generation to glucose consumption by SKF120101 cultivated in BFCS was higher under light than dark condition. The carotenoid produced by SKF120101 catalyzes production of reducing power from light energy, first evaluated by the electrochemical technique used in this research.

• Journal of Microbiology and Biotechnology
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• 제23권10호
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• pp.1460-1471
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• 2013

Microalgal biofuel production from wastewater has economic and environmental advantages. This article investigates the lipid production from high chemical oxygen demand (COD) bioethanol wastewater without dilution or additional nutrients, using a newly isolated heterotrophic microalga, Chlorella vulgaris LAM-Q. To enhance lipid accumulation, the combined effects of important operational parameters were studied via response surface methodology. The optimal conditions were found to be temperature of $22.8^{\circ}C$, initial pH of 6.7, and inoculum density of $1.2{\times}10^8cells/ml$. Under these conditions, the lipid productivity reached 195.96 mg/l/d, which was markedly higher than previously reported values in similar systems. According to the fatty acid composition, the obtained lipids were suitable feedstock for biodiesel production. Meanwhile, 61.40% of COD, 51.24% of total nitrogen, and 58.76% of total phosphorus were removed from the bioethanol wastewater during microalgal growth. In addition, 19.17% of the energy contained in the wastewater was transferred to the microalgal biomass in the fermentation process. These findings suggest that C. vulgaris LAM-Q can efficiently produce lipids from high-concentration bioethanol wastewater, and simultaneously performs wastewater treatment.

• KSBB Journal
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• 제30권3호
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• pp.125-131
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• 2015

Kluyveromyces marxianus is a well-known thermotolerant yeast. Although Saccharomyces cerevisiae is the most commonly used yeast species for ethanol production, the thermotolerant K. marxianus is more suitable for simultaneous saccharification and fermentation (SSF) processes. This is because enzymatic saccharification usually requires a higher temperature than that needed for the optimum growth of S. cerevisiae. In this study, we compared the fermentation patterns of S. cerevisiae and K. marxianus under various temperatures of fermentation. The results show that at a fermentation temperature of $45^{\circ}C$, K. marxianus exhibited more than two fold higher growth rate and ethanol production rate in comparison to S. cerevisiae. For SSF using starch or corn stover as the sole carbon source by K. marxianus, the high temperature ($45^{\circ}C$) fermentations showed higher enzymatic activities and ethanol production compared to SSF at $30^{\circ}C$. These results demonstrate the potential of the thermotolerant yeast K. marxianus for SSF in the industrial production of biofuels.