Earticle

본 연구에서는 미세조류와 박테리아의 공생관계를 이용하여 하수 내 영양염류 제거효율을 평 가하고자 하였다. 또한 최 적 배양조건을 도출하기 위해 온도, 광주기, CO2 주입농도에 따른 Chlorella sp.와 Scenedesmus sp.의 생장특성을 파악하 고, 그에 따른 영양염류 제거효율을 평가하여 미세조류-박테리아의 공생관계를 이용한 폐수 처리 가능성을 연구하였다. 그 결과 미세조류의 최적 배양조건은 25 ~ 30oC, 24시간 내내 광원을 주입해 준 경우, Chlorella sp.는 5% CO2 주입농도 에서, Scenedesmus sp.는 2% CO2 주입농도에서 높은 성장률을 기준으로 산정되었다. 산정 된 배양조건을 영양염류 제거 효율을 평가해본 결과, Chlorella sp.의 경우 COD 63%, BOD 70%, SS 48.3%, T-N 70.5%, T-P 76.4% 나타냈고, Scenedesmus sp.는 COD 66%, BOD 72.3%, SS 56.5%, T-N 67.1%, T-P 70.1%로 나타내었다 .

This study intended to evaluate the removal efficiency of nutrients in wastewarer using the symbiosis relationship of microalgae-bacteria. Also, in order to confirm optimal culture conditions, growth characteristics of Chlorella sp. and Scenedesmus sp. on the temperature, L:D cycle, and CO2 injection were identified, and then the possibility of wastewater treatment by the symbiosis relationship of microalgae-bacteria through the evaluation of nutrients removal efficiency, was identified as well. As the results, Chlorella sp. showed the highest growth rate at 25 ~ 30oC, 24:0 L:D cycle, and 5% of CO2 injection concentration, and Scenedesmus sp. showed it from 25 ~ 30oC, 24:0 L:D cycle, and 2% CO2 injection concentration, respectively. In addition, the nutrients removal efficiency under the optimal culture conditions was resulted in the followings: Chlorella sp. showed the removal efficiency of COD 63%, BOD 70%, SS 48.3%, T-N 70.5%, and TP 76.4% and Scenedesmus sp. showed COD 66%, BOD 72.3%, SS 56.5%, T-N 67.1%, and T -P 70.1%, respectively.

2018년 4월부터 2023년 3월까지 대한민국 전국의 호수와 저수지, 소류지 등을 대상으로 총 17개 지역에서 미세조류 자생종에 대한 조사를 실시하였다. 국내 새롭게 관찰된 미세조류는 2강 11목, 17과 20속, 36종(3변종, 1품종 포함)을 확인하였다. 그 중 돌말류는 1강 7목, 10과 13속, 27종(3변종 포함)으로 관찰되었고, 와편모조류는 1강 4목, 7과 7속, 9종(1품종 포함)으로 조사되었다. 본 연구에서는 종의 명명 법, 참고 문헌, 사진, 생태 및 분포에 대해서 설명을 하였다. 국내 신규 돌말류 27종은 Hantzschia dorgaliensis, Tryblionella persuadens, Delicatophycus montana, Placoneis dicephala, Gomphonema trigonocephalum, Eunotia boreoalpina, E. cisalpina, E. incisadistans, E. latiaenia, E. latinasuta, E. lewisii, E. metamonodon, E. ossicula, E. pseudosudetica, E. sedina, Staurosirella neopinnata, Frustulia inculta, F. krammeri, Neidium tibetianum, Ne. triundulatum, Ne. zoigeanum, Pinnularia abaujensis var. linearis, Pinnularia borealis var. subislandica, P. reichardtii, Epithemia adnata var. saxonica, Iconella kusberi, Surirella tientsinensis으로 동정되었다. 국내 신규 와편모조류 9종은 Ceratium brachyceros, C. furcoides, C. hirundinella f. austriacum, Gymnodinium palustriforme, Unruhdinium kevei, Glochidinium penardiforme, Parvodinium elpatiewskyi, Tyrannodinium edax, Chimonodinium godlewskii 으로 확인되었다. 새롭게 관찰된 미세조류들은 종별 서식환경의 차이를 보여주었다. 이 연구는 한국에 미세조류의 다양성 증대에 기여하며, 국내에서 자생하는 미세조류에 대한 기초 연구자료로서 활용성이 크다고 사료된다.

From April 2018 to March 2023, a survey of indigenous microalgal species was conducted across 17 locations nationwide in South Korea, covering freshwater lakes, reservoirs, and ponds. Newly observed microalgae in South Korea included 2 classes, 11 orders, 17 families, 20 genera, 36 species, 3 varieties, and 1 forma. Among them, diatoms were categorized as 1 class, 7 orders, 10 families, 13 genera, and 27 species (including 3 varieties). Dinoflagellates were recorded as 1 class, 4 orders, 7 families, 7 genera, and 9 species (including 1 forma). This study describes the species' nomenclature, references, photographs, ecology, and distribution. The 27 newly recorded diatom species in South Korea include Hantzschia dorgaliensis, Tryblionella persuadens, Delicatophycus montana, Placoneis dicephala, Gomphonema trigonocephalum, Eunotia boreoalpina, E. cisalpina, E. incisadistans, E. latiaenia, E. latinasuta, E. lewisii, E. metamonodon, E. ossicula, E. pseudosudetica, E. sedina, Staurosirella neopinnata, Frustulia inculta, F. krammeri, Neidium tibetianum, Ne. triundulatum, Ne. zoigeanum, Pinnularia abaujensis var. linearis, Pinnularia borealis var. subislandica, P. reichardtii, Epithemia adnata var. saxonica, Iconella kusberi, and Surirella tientsinensis. The 9 newly recorded dinoflagellate species in South Korea include Ceratium brachyceros, C. furcoides, C. hirundinella f. austriacum, Gymnodinium palustriforme, Unruhdinium kevei, Glochidinium penardiforme, Parvodinium elpatiewskyi, Tyrannodinium edax, and Chimonodinium godlewskii. The newly observed microalgae showed differences in habitat preferences by species. This study is considered valuable as foundational research data for expanding the understanding of microalgal diversity in South Korea.

목적: 본 연구는 Scenedesmus deserticola JD052 (JD052) 추출물을 포함하는 토너, 로션, 크림의 자외선에 의한 손상 피부 자극진정효과와 진피치밀도, 주름, 진피 보습 개선에 대한 인체 효능을 평가하는 것을 목적으로 한다. 방법: 선정기준 및 선정제외기준에 기초하여 29세 이상의 성인 여성 22명을 피시험자로 선정하였다. 피시험자는 시험기간인 4주 동안 매일 아침, 저녁으로 세안및 왼쪽 상완 부위를 세정 후, JD052 추출물이 함유된 시험물질인 토너, 로션, 크림을 동일한 양으로 순서대로 안면부위와 왼쪽 상완의 지정된 시험부위에 고르게 펴 발라 흡수시켰다. 시험물질의 자외선에 의한 손상 피부 자극 진정효과를 평가하기 위하여 solar simulator와 ANTERA 3D를 적용하여 측정하였으며, 진피치밀도 개선평가는 DUB®SkinScanner를 이용하여 측정하였다. 주름 개선 평가는 ANTERA 3D를 적용하여 측정하였으며, 진피 보습 개선 평가는 MoistureMeterD Compact를 이용하여 측정하였다. 결과: 시험물질 사용 전과 비교하여 2주 및 4주 사용 후, 피부 붉은기를 나타내는 a* value가 각각 5.30%, 5.54% 감소하였으며, 진피치밀도는 각각 12.08%, 21.15% 증가하였다. 피부 주름을 나타내는 wrinkles small value는 각각 5.58%, 8.35% 감소하였으며, 진피 수분은 시험물질 사용 전과 비교하여, 1회 사용 직후, 2주 및 4주 사용 후가 각각 23.54%, 4.32%, 6.48%로 증가되었다. 결론: JD052 추출물을 포함하는 토너, 로션, 크림은 자외선에 의한 손상 피부 자극 진정효과와 진피치밀도, 주름, 진피 보습 개선에 도움을 주는 것으로 사료된다.

Purpose: The aim of this clinical study was to evaluate the effects of toner, lotion, and cream containing Scenedesmus deserticola JD052 (JD052) extract on ultraviolet (UV) induced skin irritation, dermal density, facial wrinkles, and dermal moisture. Methods: 22 female volunteers over 29 years of age were selected on the basis of predetermined inclusion and exclusion criteria. Every morning and night for 4 weeks, each subject washed their face and left upper arm and then applied the same amount of each test material on these areas in the following sequence: toner, lotion, and cream. The following effects were then evaluated: the skin soothing effect on UV-induced skin irritation using a solar simulator and the ANTERA 3D Dermal Imaging Device; dermal density improvement using the DUB®SkinScanner; facial wrinkle improvement using the ANTERA 3D; and dermal moisture improvement using the MoistureMeterD Compact. Results: After 2 and 4 weeks, respectively, of application of the test materials, the a * value, which indicated skin redness, was reduced by 5.30% and 5.54%, dermal density was increased by 12.08% and 21.15%, and the wrinkles small value, which indicates the number of skin wrinkles, was decreased by 5.58% and 8.35% compared with pretreatment levels. Furthermore, dermal moisture was increased by 23.54%, 4.32%, and 6.48% immediately, 2, and 4 weeks, respectively, after application of the test materials compared with pre-treatment levels. Conclusion: Toner, lotion, and cream containing JD052 extract were found to have a skin soothing effect on UV-induced skin irritation and to improve dermal density, facial wrinkles, and dermal moisture.

目的: 探索含有Scenedesmus deserticola JD052（JD052）提取物的化妆水，乳液和面霜对UV诱导损伤皮肤的皮肤刺激 镇静作用以及改善皮肤密度，皱纹和皮肤保湿作用的效果。 方法: 根据预先设定的纳入和排除标准，选出了年龄在29岁 以上的22名女性受试者。每个早晚各4周，每个受试者每天洗脸和左上臂，然后按照化妆水，乳液和面霜顺序在这些部位 上涂抹相同量。为评价紫外线损伤皮肤的镇静效果，使用solar simulator和ANTERA 3D来进行测定；皮肤密度改善效果 利用DUB®SkinScanner来测定；面部皱纹改善利用ANTERA 3D来测定; 皮肤水分改善效果利用MoistureMeterD Compact 来测定。 结果: 使用试验材料2周和4周后，皮肤的a*值分别降低了5.30％和5.54％；皮肤密度分别增加了12.08％和 21.15％；显示皱纹的wrinkles small value分别降低了5.58％和8.35％。此外，施用试验材料后，皮肤水分分别比施用前 相比，分别提高了23.54％（使用1次后），4.32％（2周）和6.48％（4周）。 结论: 含有JD052提取物的化妆水，乳液和 面霜被发现对紫外线诱导的皮肤刺激具有皮肤舒缓作用，并改善皮肤密度，面部皱纹和皮肤水分。

본 연구는 역삼투 농축수의 생물복원 과정에서 Scenedesmus quadricauda 미세조류가 난분해성 유기물질의 분해와 이 용에 어떻게 관여하는지에 대하여 조사하였다. 조류를 이용하여 역삼투 농축수를 처리한 결과, 염도 500 및 8000 mg Cl- /L, 연속폭기(10% CO2), 그리고 간헐조명(L/D=16/8) 조건에서 용존유기물질의 생분해도 향상과 무기영양염류의 높은 제 거율을 확인할 수 있었다. 본 연구에서는 조류 처리수로부터 과산화수소 농도를 측정하여 조류에 기인하는 난분해성 유 기물질의 분해 메커니즘을 평가하였다. 세포 성장과정에서 유기탄소원의 이용이 가능한 조류를 농축수와 같은 난분해성 폐수처리에 적용하는 경우 영양염류의 동시 제거가 가능하다는 점에서 일반적으로 사용되는 전기화학적 산화기술보다 지속가능성과 비용효율 면에서 상대적으로 그 적용성이 높다고 평가 할 수 있다.

This study explored how Scenedesmus quadricauda microalga is involved in the degradation and subsequent assimilation of refractory organic matter during remediation of reverse osmosis concentrate. The algal cells were cultivated in the reverse osmosis concentrate with low to high salinities under the given conditions, which resulted in a remarkable increase in the biodegradability of dissolved organic matter, along with robust removal of nutrients (N and P). In this study, hydrogen peroxide from algal-treated wastewater was measured to investigate the mechanism of organic deformation which was associated with algal growth. The degradation of refractory organic matter with microalgae can be considered as more sustainable and cost-effective when compared to commonly used electrochemical oxidation techniques.

From the time of the industrial revolution, fossil fuel has been the main source of energy, acting as a stimulant for many modernized industries. Despite the positive changes fossil fuel has brought to the mankind, it has produced carbon emission, facilitating the rising temperature of Earth resulting in global warming. Limited supply of fossil fuel has also hastened the search for alternative sources of energy. Biofuel from microalgae is recently gaining attention for its environmental friendliness, for example CO2 fixation during cultivation and high lipid content. Two strains of microalgae are used, Botryococcus braunii and Nannochloropsis oceanica, for their high potential as biofuel sources. Different colored settings of LED light, Green, Red, White, Blue, Red: Blue = 5:1, Red: Blue 3:1, Red: Blue = 1:1 were controlled to investigate the effects of mixture of colors on growth and lipid content of microalgae. Spectrophotometry and fluorescence spectrophotometry were used to measure the growth and lipid content of each microalgae strain. The experiment was conducted over the period of eight days, with measurements done on day 0,2,4,6, and 8. The optimum color of light differed slightly between strains, with B. braunii Red: Blue = 5:1 and N. oceanica red. The mixture of red and blue LED light had the better growth and lipid content than the single colored lights, red and blue mixed light with 18% more lipid content than white light in Botryococcus braunii. The ultimate light conditions for the cultivation of microalgae vary among species, but the best outcomes can be expected from using a mixture of red and blue lights. To find the optimum light ratio for each microalgae strain, further research and experiments using various ratio mixtures of red and blue lights are essential.

본 연구에서는 방사성 폐액내 포함된 방사성 핵종인 세슘-137(Cs-137) 및 스트론튬-90(Sr-90)의 친환경적인 제염을 위해 미세조류의적용 가능성을 평가하였다. Cs-137 및 Sr-90이 각각 함유된 일원계 표준 방사성 용액과 3차 증류수를 희석하여 1.5 Bq/mL Cs-137, 1.0 Bq/mL Sr-90 농도로 제조한 뒤 실험에 사용하였다. 미세조류는 2종을 사용했으며, Sr-90 제염에는 Chlorella Vulgaris를 사용하였고, Cs-137 제염에는 Hematococcus pluvialis를 사용하여 실험을 수행하였다. 실험 방법은 2주 간 배양된 미세조류를 반투과막이 부착된 병에 투입한 뒤, 미세조류가 투입된 병을 제조된 방사성 용액에 투입하여, 반투과막을 통해 미세조류와 방사성 용액이 48 시간 동안 반응하도록 하였다. 각 시료에 대한 방사능 농도 분석은 γ선 동위원소인 Cs-137은 감마선 핵종 분석기를 사용하였고, β선 동위원소인 Sr-90은액체섬광계수기(LSC: Liquid Scintillation Count)를 사용하였다. 실험 결과, Cs-137은 약 88.0 %, Sr-90은 약 89.7 % 제염이 가능함을 확인하였으며, Sr-90은 2단 제염 방법에 의해 최종적으로 약 98.6 % 제염이 가능하였다.

In this study, the applicability of microalgae was evaluated for eco-friendly decontamination of cesium-137 (Cs-137) and strontium-90 (Sr-90), which are radioactive nuclides contained in radioactive waste. The monolithic radioactive solution used in the experiment was manufactured at a concentration of 1.5 Bq/mL Cs-137 and 1.0 Bq/mL Sr-90 by diluting a standard radioactive solution and distilled water. This experiment used two types of microalgae, Chlorella Vulgaris was used for Sr-90 decontamination and Hematococcus pluvialis for Cs-137 decontamination. The experimental method is to put the microalgae cultured for 2 weeks into a bottle with a semi-permeable membrane, and then put the bottle in which the microalgae was put into the manufactured radioactive solution, so that the microalgae and the radioactive solution react through the semi-permeable membrane for 48 hours. For the radioactivity concentration analysis of each sample, a gamma-ray nuclide analyzer was used for Cs-137, a γ -ray i sotope, and a Liquid S cintillation Count(LSC) w as u sed f or Sr-90, a β -ray i sotope. As a r esult of the experiment, it was confirmed that about 88.0 % of Cs-137 and about 89.7 % of Sr-90 could be decontaminated, and about 98.6 % of Sr-90 was finally able to be decontaminated by the two-stage decontamination method.

최근 환경 문제로 대두되고 있는 것 중 하나는 대기 중 CO2의 증가로 인한 기후변화이다. 이에 대한 영향으로 생태계가 변화하고 있으며, 다양한 환경문제가 발생되고 있다. 이로 인해 전 세계적으로 CO2 저감을 위한 다양한 연구들이 수행 중이며, 이 중 미세조류를 이용한 CO2 저감 방안은 환경 친화적인 방법이라 할 수 있다. 그러나 미세조류를 이용한 CO2 저감 방안은 대부분 단일 종을 대상으로 하고 있으며, 자연 하천을 대상으로 한 미세조류의 CO2 고정 효율에 대한 연구는 전무한 실정이다. 그러므로 본 연구는 우리나라 하천 내 존재하는 미세조류들을 파악하고, 미세조류의 생장특성을 분석하여 최적의 배양조건을 도출 하였다. 그리고 CO2 농도와 주입 속도에 따른 미세조류의 biomass와 클로로필 a의 변화를 분석하여 자연 하천 내 존재하는 미세조류의 CO2 고정효율에 대해 연구하고자 하였다. 섬강 내 존재하는 미세조류를 배양하여 동정한 결과 6종의 우점종(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum)이 관찰되었으며, 이 종들은 모두 녹조류에 해당하였다. 한편 이산화탄소 농도 구배(5% CO2, 10% CO2, 15%CO2, 대기조건의 가스 0.038% CO2)와 유속(0.25, 0.5LPM)이 다른 가스를 주입하여 미세조류의 biomass와 클로로필 a의 변화를 살펴본 결과 이산화탄소의 농도가 증가 할수록 biomass와 클로로필 a가 증가하였으며, 같은 이산화탄소 농도에서는 유속이 더 빠른 곳에서 미세조류의 biomass와 클로로필 a의 양이 더 증가하였다. 또한 미세조류에 고정화된 이산화탄소의 양은 주입되는 가스의 유속이 빠를수록 고정 되는 이산화탄소의 양이 더 높아지는 경향을 보였다. 본 연구는 기존의 단일 종에서 행해지는 연구가 아닌 하천 전체의 미세조류를 대상으로 수행한 연구이며, 하천 내 존재하는 미세조류의 이산화탄소 고정을 위한 최적의 조건을 도출하고, 하천 내 존재하는 미세조류로부터 고정화된 이산화탄소의 양을 정량화하여 향후 이산화탄소 감축을 위한 정책을 위한 기초자료에 이용할 수 있다는 것에 큰 의의가 있다.

One of the recent environmental problems is climate change due to the increase of atmospheric CO2, which causes ecological changes and various environmental problems. Therefore, various studies are being carried out to reduce CO2 in the world in order to solve various environmental problems caused by increase of CO2. The CO2 reduction using microalgae is an environmentally friendly method by using photosynthesis reaction of microalgae. However, most studies using single species. There is no study on the CO2 fixing efficiency of microalgae in natural rivers. Therefore, this study was to identify the microalgae in the Sum river and to analyze the growth characteristics of microalgae in the river to obtain optimal culture conditions. And the changes of biomass and chlorophyll-a of microalgae were analyzed according to CO2 concentration and injection rate. The purpose of this study was to investigate the fixing efficiency of carbon dioxide in microalgae in natural rivers. Six kinds of dominant species were observed as a result of the identification of microalgae in Sum river(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum ). All of these species were green algae. Biomass and chlorophyll-a increased with the increase of CO2 concentration and biomass and chlorophyll-a increased faster flow rate at the same CO2 concentration. Also, the quantity of CO2 fixation on the microalgae tended to be higher when the flow rate of injected gas was faster. This study can be referred as being significant in the micro-algae in river. In addition, the optimal conditions for CO2 fixation of microalgae in rivers and the quantification of the quantity of CO2 fixation from microalgae in rivers can be used as basic data for future policy of CO2 reduction.

The future resources for food, fuels, and chemicals potentially come from ocean. One of the major marine resources is microalgae, which have the ability to fix carbon dioxide at a much faster rate than that of terrestrial plants. The fixed carbon dioxide is converted to microalgal biomass, which has potential applications in producing biofuels, animal feed, health food, pharmaceuticals, and other high-value products. Therefore, using microalgae to mitigate CO2 emissions is a promising strategy for CO2 storage and utilization. We have identified various indigenous microalgae strains that utilize flue gas of a steel-making factory for growth with excellent CO2 biofixation ability. We are able to adjust the composition of resulting microalgal biomass (lipid, carbohydrates, proteins, pigments, etc.) by using different cultivation strategies to meet the needs of downstream applications. To make the concept of microalgae industry a realty, many new technologies and engineering approaches should be developed (for instance, outdoor large-scale cultivation, biomass harvesting, product conversion technology, etc.). Some key technologies required for realizing commercialization of microalgae-based CO2 emission mitigation and biorefinery are introduced in this presentation.

Global warming and the exhaustion of fossil fuels are major world-wide problems. Thus, the production of biodiesel using various materials, such as plants, microalgae, and animal fat, has been attempted as an alternative energy source. In particular, biodiesel has two main advantages, the mitigation of carbon dioxide and as a substitute for petroleum. Microalgae also have certain advantages compared to other energy crops, including a high growth rate, short growth time, high biomass production, and low land use.The key processes involved in biodiesel production using microalgae are cultivation, harvest, lipid extraction and the transesterification of the lipids. In order to extract lipids from algal biomass, organic solvents such as hexane and a mixture of chloroform and methanol are typically used. However, the health, security, and regulatory problems associated with the use of organic solvents should be addressed. In addition, efficient solvent recovery processes are needed to commercialize these processes. Therefore, several groups have reported the use of supercritical CO2, less toxic solvent mixtures, and ionic liquids (ILs) to replace toxic organic solvents. Ionic liquids (ILs) composed entirely of ions are liquid at room temperature. Since they have negligible vapor pressure, non-flammability, and tunable physiochemical properties for a particular application which term them as “designer solvents”, ILs have recently gained much attention as alternatives for organic solvents in many processes. In particular, ILs have been used to extract protein from aqueous two phase systems, extract hormones from urine samples, and be used as alternative solvents for liquid–liquid extraction. Therefore, the direct extraction of lipid from microalgae using ILs are demonstrated in this study.

Conversion of microalgae to biodiesel typically includes the following four steps: microalgae cultivation, cell harvesting, lipid extraction, and biodiesel conversion. A number of methods can be used to achieve lipid extraction from microalgae, including solvent extraction, cracking, supercritical extraction, pyrolysis, enzymatic hydrolysis, and osmotic shock. Many researchers have recovered microalgal lipids from dried microalgae. However, the lipid extraction from wet microalgae has to be developed because the dewatering process to obtain dried microalgae is costly. The studies on wet lipid extraction have been very limited. In this study, the feasibility of lipid extraction and biodiesel production from wet microalgae was investigated. The microalgal lipid was extracted from wet microalgae by hot-water pretreatment. To enhance the lipid extraction yield, chemicals were added to microalgal solution. The lipid extraction yields under various experimental conditions were examined. After that, the microalgal biodiesel was produced by transesterification using sulfuric acid-methanol solution. After distillation, light-yellow biodiesel was obtained from dark-green biodiesel.

In this study, sequential strategy based design was applied to optimize the microalgae, Pavlova lutherimass culture conditions and fermentation conditions of the cultured algae by proteolytic yeast Candidiarugopelliculosa to obtain small peptide chains. This optim ization of culture and fermentation conditionsby response surface methodology (RSM) finally leads to effective purification of a bioactive peptideMPGPLSPL (793.01 Da) with hydroxyl radical scavenging activity. Collectively, these results indicated thatmicroalgae P. lutheri can enhance the hydroxyl radical inhibiting effect through protein hydrolysis processunder RSM optimal condition.

Recently, the potential use of microalgae as a source of biomass for fuel production has been focused because microalgae have advantages as a feedstock for energy production; they can be cultivated easily and are not considered to be human food sources. In this study, the anaerobic digestion (AD) process using microalgae as a substrate was investigated to see the possibility of methane production. Microalgae should be pretreated before adding into AD process in order to improve the biodegradability of organic materials. Herein, thermal, chemical, ultrasonic, and combined pretreatments were examined to find the optimum condition of pretreatments. The result showed that thermal, alkali, ultrasonic pretreatment were relatively effective, and their combinations were more effective than individual pretreatment in terms of cell lysis activity. Vial tests were performed by two combined (alkali/ultrasonic, ultrasonic/thermal) and two individual (thermal, ultrasonic) pretreated biomass of Dunaliella sp., and two mesophilic sludges obtained from municipal wastewater treatment plant (WTPSL) and local brewing company (BRSL) were used for inoculum sources. Pretreated biomass was spiked two times into vials containing anaerobic medium and inoculum sources, and methane production was measured up to 60 days. Consequently, as a control 0.752 and 0.198 L CH4/g TCOD were generated from WTPSL and BRSL itself, respectively. Vial containing pretreated microalgae produced 0.7–.2 times higher methane yields than negative control. Results also indicated that vial with combined pretreated microalgae extracted more methane gas compared to vial with un-pretreated microalgae. Therefore, it was demonstrated that microalgae have a potential to be a substrate in AD, and pretreatment have a positive effect on extracting more methane gas in AD.

Biodiesel from microalgae is expected to be a desirable, renewable biofuel that can replace petroleum-derived transport fuels. However, the development of a cost-effective harvesting method is required to reduce the production cost and realize the economic feasibility. A partial factorial design was used to screen the main factors among several inorganic coagulants and bioflocculants. These factors were different, depending on the algal genera. Response surface methodology was used to further investigate the optimal conditions for these factors on flocculation of Scenedesmus sp. and Botryococcus braunii. Analysis of variance and other relevant tests, such as lack of fit and residual probability plots, confirmed the validity of the suggested empirical model. The optimal flocculation conditions could be easily derived using the obtained equation. The experimentally determined flocculating activities corresponded with the estimated values. The equation suggested using response surface methodology could be applied to optimize harvesting conditions and minimize the related costs of biodiesel production.

Biodiesel production from microalgae has been recently expected to replace the petroleum-based energy sources owing to its high areal productivity and lipid contents. However, large-scaled algae cultivation for biodiesel production should be significantly improved to compete with the cost of present fossil-based energy. In order to reduce the input cost for microalgal cultivation, we investigated the utilization of blended wastewaters taken from domestic and livestock wastewater treatment plants (WWTP). A Chlorella species isolated from Nacdong River effectively utilized the nutrients dissolved in the blended wastewaters. After 10 days cultivation under 200 μmol/m2/s cool-white fluorescent light and 25±1 ℃, significantly high maximum biomass production of c.a. 5.0 g-dry cell weight/L was obtained from the combined wastewater of a domestic WWTP influent and the livestock WWTP effluent without any pretreatment of those wastewaters. The optimal concentration range of the total nitrogen was 100-200 mg/L. These results demonstrated that blended wastewaters would be utilized for mass cultivation of microalgae as both water and nutrient sources.

Since Korea is highly relying on imported fossil fuels for transportation, sourcing alternative renewable and eco-friendly transportation fuel remains highly pertinent. Long been microalgae are looked at as a suitable source of alternatives for fossil fuel and efficient CO2 mitigators. In spite of the remarkable advantages, microalgal biodiesel production still remains an expensive technology, and commercially viable large -scale algal production has yet to be achieved.This study focused on mass-cultivation of oleaginous microalgae under autotrophic and mixotrophic conditions with low-cost photobioreactors. Several species of microalgae from natural environments and microalgal culture bank were screened for their ability to grow autotrophically and mixotrophically (glucose/glycerol) with high CO2 concentrations (often 10% and coal-fired flue gas). As a result, a few microalgae spp. were identified with high growth rates and lipid content (~40 % to their dry cell mass). When the selected isolates were grown in 1 L bubble column under different nutritional modes, mixotrophic mode yielded the maximum growth when compared to the autotrophic or heterotrophic mode of cultivation. Several analyses are being instigated for detailed characterization of the cultivation of microalgal isolates, which includes; 18S rRNA gene sequencing, changes in pH and optical density of the culture, microscopic analyses (light microscopy, SEM and TEM analysis), estimation of lipid content, characterization of Fatty Acid Methyl Ester (FAME) profiles, estimation of carbohydrates, protein and chlorophyll, measurement of cell size/numbers, rate of glucose/glycerol consumption, rate of nitrate, phosphate and CO2 consumption, production of organic acid metabolites, and Denaturing Gradient Gel Electrophoresis (DGGE) for community analysis of epiphytic bacteria associated with microalgae in culture. For mass cultivation studies, photobioreactors were designed with transparent films and various prototypes of working volume 3 to 30 L are being evaluated for their efficiency to utilize CO2 and flue gas from a 2 MW coal power plant under indoor and outdoor conditions. This talk would discuss the recent experimental data and future directions of the study.

Microalgae are one of potential carbon resources from ocean. The microalgae have been used for live feeds, cosmetics, biomedicine and the production of biodiesel. In this study, the determination of lipid contents was carried out from 3 marine microalgae. Phaeodactylum tricornutum, Nannochloropsis oculata, Isocrysis galbana were selected due to high oil contents in cell body comparing to the other strains. Inoculation densities of the microalgae were optimized for the scale-up process. Nitrate as limiting nutrient source was monitored by UVspectrophotometer for the accumulation of lipid. Lipid contents of the strains harvested 3, 6 and 9 days after stationary phase were determined using Soxhlet extractor. Nitrate source was exhausted before stationary phase. The specific growth rates of P.tricornutum and N.oculata were 0.25 cells/ml/day, 0.27 cells/ml/day and 0.20 cells/ml/day, respectively. N.oculata could maintain high specific growth rate and cell density (1.5~10folds) in stationary phase. Further studies are focused on the increase of lipid contents in the microalgae.

Cell walls of microalgae consist of a polysaccharide and glycoprotein matrix providing the cells with a formidable defense against its environment. Anaerobic digestion (AD) of microalgae is primarily inhibited by the chemical composition of their cell walls containing biopolymers able to resist bacterial degradation. Adoption of pre-treatments such as thermal, thermal hydrolysis, ultrasound and enzymatic hydrolysis have the potential to remove these inhibitory compounds and enhance biogas yields by degrading the cell wall, and releasing the intracellular algogenic organic matter (AOM). This paper preproposal stage investigated the effect of different pre-treatments on microalgae cell wall, and their impact on the quantity of soluble biomass released in the media and thus on the digestion process yields. This Paper present optimum approach to degradation of the cell wall by ultra-sonication with practical design specification parameter for ultrasound based pretreatment system. As a result of this paper presents, a microalgae system in a wastewater treatment flowsheet for residual nutrient uptake can be justified by processing the waste biomass for energy recovery. As a conclusion on this result, Low energy harvesting technologies and pre- treatment of the algal biomass are required to improve the overall energy balance of this integrated system.