• Journal of Microbiology and Biotechnology
• /
• 제10권6호
• /
• pp.817-822
• /
• 2000

A proper flashing light is expected to enhance microalgal biomass productivity and photosynthetic efficiency. The effect of flashing light on high-density Chlorella kessleri (UTEX 398) cultures was studied using light-emitting diodes. A frequency modulator was designed to flash LEDs, and the device successfully provided wide range of frequencies and various duty cycles of flashing. A relatively high frequencies of 10, 20 and 50 kHz were used in this study. These frequencies have very short flashing time ($2-50{\mu}s$), which corresponded to the time constant of the light reaction of photosynthesis. The specific oxygen production rates of photosynthesis under flashing light were compared with those under an equivalent continuous light in specially designed illumination cuvette. The specific oxygen production rates under flashing light were 5-25% higher than those under the continuous light. A range of cell concentration was discovered, where the benefit of flashing light was maximized. The photosynthetic efficiency was also higher under flashing light with frequencies of over 1 kHz, which was a clear indication of flashing light effect and the degree of mutual shading could by overcome by flashing lights, particularly at high-density algal cultures.

• Korean Chemical Engineering Research
• /
• 제56권5호
• /
• pp.773-778
• /
• 2018

In-situ transesterification of microalgae lipids using microwave irradiation has potential to simplify and accelerate biodiesel production, as it minimizes production cost and reaction time by direct transesterification of microalgae into biodiesel with microwave as a heating source. This study was conducted to research the effect of microwave irradiation with in-situ transesterification of microalgae under base catalyst condition. The process variables (reaction time, solvent ratio, microwave power) were studied using 2% of catalyst concentration. The maximum yield of FAME was obtained at about 32.18% at the reaction time of 30 min with biomass-methanol ratio 1:12 (w/v) and microwave power of 450 W. The GC MS analysis obtained that the main component of FAME from microalgal oils (or lipids) was palmitic acid, stearic acid and oleic acid. The results show that microwaves can be used as a heating source to synthesize biodiesel from microalgae in terms of major components resulting.

• 한국농공학회논문집
• /
• 제52권6호
• /
• pp.19-26
• /
• 2010

Batch experiments were conducted to investigate growth and nutrient removal performance of microalgae Chlorella vulgaris by using piggery wastewater in different concentration of pollutants and the common growth models (logistic, Gompertz and Richards) were applied to compare microalgal growth parameters. Removal of nitrogen (N) and phosphorus (P) by Chlorella vulgaris showed correlation with biomass increase, implying nutrient uptake coupled with microalgae growth. The higher the levels of suspended solids (SS), COD and ammonia nitrogen were in the wastewater, the worse growth of Chlorella vulgaris was observed, showing the occurrence of growth inhibition in higher concentration of those pollutants. The growth parameters were estimated by non-linear regression of three growth curves for comparative analyses. Determination of growth parameters were more accurate with population as a variable than the logarithm of population in terms of R square. Richards model represented better fit comparing with logistic and Gompertz model. However, Richards model showed some complexity and sensitivity in calculation. In the cases tested, both logistic and Gompertz equation were proper to describe the growth of microalgae on piggery wastewater as well as easy to application.

• 공업화학
• /
• 제32권5호
• /
• pp.487-496
• /
• 2021

Microalgae is one of the promising biodiesel feedstock with high growth rates compared to those of terrestrial oil crops. Despite its numerous advantages, biodiesel production from microalgae needs to reduce energy demand and material costs further to go to commercialization. During solvent extraction of microalgal lipids, lipid-extracted algae (LEA) cell residue is generated as an organic solid waste, about 80-85% of original algal biomass, and requires an appropriate recycling or economic disposal. The resulting LEA still contains significant amount of carbohydrates, proteins, N, P, and other micronutrients. This review will focus on recent advancement in the utilization of LEA as: (i) utilization as nutrients or carbon sources for microalgae and other organisms, (ii) anaerobic digestion to produce biogas or co-fermentation to produce CH₄ and H₂, and (iii) conversion to other forms of biofuel through thermochemical degradation processes. Possible mutual benefits in the integration of microalgae cultivation-biodiesel production-resulting LEA with anaerobic digestion and thermochemical conversion are also discussed.

• 한국기계가공학회지
• /
• 제20권8호
• /
• pp.33-41
• /
• 2021

Recently, many studies have been conducted on substituting fossil fuels with bio-refineries in existing industrial systems using biomass. Among the various bio-refineries, microalgae have received wide attention because it uses inorganic compounds to produce useful substances, which are extracted by a cell disruption process. Although numerous cell disruption methods exist, cell disruption efficiency has been studied by ultrasonic treatment. Ultrasound is a high-frequency (20 kHz or higher) sound wave and causes cell disruption by cavitation when passing through a solvent. In this study, we used the microalgal species Chlorella sp., which was cultured in a plate-type photobioreactor. The experiment was conducted using a continuous low-frequency processing device. The reduction of cells with time due to cell disruption was fitted using a logistic model, and optimum conditions for highly efficient cell disruption were determined by conducting experiments under multiple conditions.

• 대한토목학회논문집
• /
• 제32권4B호
• /
• pp.253-259
• /
• 2012

하수에서 배양된 미세조류인 Chlorella vulgaris AG10032, Ankistrodesmus gracilis SAG278-2, Scenedesmus quadricauda AG10308은 오폐수에서 질소 및 인 제거가 우수하고 높은 지질을 함유하고 있어서, 오폐수에서 바이오연료나 기타 바이오 기반의 자원 회수에 유용한 생물자원이다. 오폐수 환경에는 다양한 인의 농도가 존재하는데, 인의 농도 특히 인 결핍조건에 따른 조류의 지방산 특성에 대한 정보가 매우 제한적이다. 이는 표준 분석방법이 정립되어 있지 않은데 일부 기인한다. 본 연구에서는 미생물의 지방산을 분석하는데 일반적으로 사용되는 무극성 컬럼법과 식물성 지질을 분석하는데 널리 사용되는 극성 WAX-type 컬럼 GC-FID 방법의 미세조류 지방산 분석 성능을 비교 분석하였고, 하수배양 조류에 적용이 보다 적절한 방법을 이용해서 인 결핍에 의한 조류 지방산 생성특성에 미치는 영향을 평가하였다. 그 결과 무극성 컬럼 방법에 비해 극성 WAX-type 컬럼 GC 방법이 $C_{18:3}$ 지방산과 같은 고불포화지방산을 규명하는 분석능력이 우수하였고, 실제 하수배양에서 배양 분리된 미세조류의 지방산 분석에 보다 정확한 결과를 보이었다. 이 WAX-type 컬럼 방법으로 인 결핍 영향을 분석한 결과, 미세조류의 지방산 조성과 생성량은 인의 농도 변화에 크게 영향을 받지 않음을 밝히었다.

• 공업화학
• /
• 제20권3호
• /
• pp.285-289
• /
• 2009

최근 지구온난화 및 식량문제에 대한 관심이 증대되면서 그 해결책으로 미세조류에 대한 많은 연구가 이루어지고 있다. 특히 광합성 미세조류 Spirulina platensis는 이산화탄소를 고정할 수 있으며, 영양적 가치가 우수하여 많은 관심을 받고 있다. 본 연구에서는 Spirulina platensis NIES 39의 대량 배양을 위한, 배양온도, 초기 pH, 조도, 탄소와 질소원의 농도 등의 요인에 대한 최적 조건을 확립하고자 하였다. 배양 온도 $35^{\circ}C$에서 초기 pH 9.5, 조도 4500 lux에서 건조균체중량 2.10 g/L, 클로로필 함량 29.53 mg/L로 가장 우수한 결과를 나타내었으며, 이때의 탄소원과 질소원의 농도는 각각 16.8 g/L $NaHCO_3$, 2.5 g/L $NaNO_3$이었다.

• ALGAE
• /
• 제35권3호
• /
• pp.277-292
• /
• 2020

Omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are polyunsaturated fatty acids beneficial to human health. A limited number of microalgae have been used for commercial omega-3 production, which necessitates the identification of new microalgae with high omega-3 contents. We explored the fatty acid composition and EPA and DHA contents of the mixotrophic dinoflagellate Gymnodinium smaydae fed with the optimal algal prey species Heterocapsa rotundata. Cells of G. smaydae were found to be rich in omega-3 fatty acids. In particular, the DHA content of G. smaydae was 21 mg g^-1 dry weight, accounting for 43% of the total fatty acid content. The percentage of DHA in the total fatty acid content of G. smaydae was the highest among the reported microalgae except for Crypthecodinium cohnii. Moreover, to determine if the prey supply interval affected the growth rate of G. smaydae and its fatty acid content, three different prey supply intervals (daily, once every 2 d, and once for 4 d) were tested. Daily prey supply yielded the highest total fatty acid and DHA contents in G. smaydae. Furthermore, we successfully produced high-density G. smaydae cultures semi-continuously for 43 d with daily prey supply. During the semi-continuous cultivation period, the highest density of G. smaydae was 57,000 cells mL^-1, with an average growth rate of 0.7 d^-1. Taken together, the percentage of EPA and DHA in the total fatty acid content was maintained in the range of 54.2-56.9%. The results of this study support G. smaydae as a promising microalgal candidate for commercial DHA production and demonstrate that daily supply of prey can efficiently produce high-density G. smaydae cultures for more than a month.

• Asian Journal of Atmospheric Environment
• /
• 제5권3호
• /
• pp.157-163
• /
• 2011

Atmospheric aerosol deposition caused by Asian dust (KOSA) events provide nutrients, trace metals, and organic compounds over the Pacific Ocean that enhance ocean productivity and carbon sequestration and, thus, influence the atmospheric carbon dioxide concentrations and climate. Using dust particles obtained from the snow layers on Mt. Tateyama and the surface sand of Loess Plateau in incubation experiments with natural seawater samples on a shipboard, we demonstrate that dust-particle additions enhanced the bacterial growth on the first day of incubation. Gram-positive bacterial group and alpha-proteobacteria were specifically detected form seawater samples including the mineral particles. Although the remarkable dynamics of trace elements and nutrients depend on dust-particle additions, it is possible that organic compounds present in the mineral particles or transported microbial cells could also contribute to an increase in the quantities of bacteria. The chlorophyll concentrations at fractions of every size indicated a similar pattern of change between the seawater samples with and without the dust-particle additions. In contrast, the chlorophyll measurement using submersible fluorometer revealed that the dynamics of phytoplankton composition were influenced by the dust-particles treatments. We conclude that the phytoplankton that uses the bacterial products would increase their biomass. We show that KOSA deposition can potentially alter the structures of bacterial communities and indirectly influence the patterns of marine primary production in the Pacific Ocean.

• Journal of Microbiology and Biotechnology
• /
• 제24권8호
• /
• pp.1123-1132
• /
• 2014

This study evaluated the growth and nutrient removal ability of an indigenous algal consortium on real untreated municipal wastewater in a high rate algal pond (HRAP). The HRAP was operated semicontinuously under different hydraulic retention times (HRT: 2, 4, 6, and 8 days). The average removal efficiencies of chemical oxygen demand, and total nitrogen and phosphate of real municipal wastewater were maintained at $85.44{\pm}5.10%$, $92.74{\pm}5.82%$, and $82.85{\pm}8.63%$, respectively, in 2 day HRT. Algae dominated the consortium and showed high settling efficiency (99%), and biomass and lipid productivity of $0.50{\pm}0.03g/l/day$ and $0.103{\pm}0.0083g/l/day$ (2day HRT), respectively. Fatty acid methyl ester analysis revealed a predominance of palmitate (C16:0), palmitoleate (C16:1), linoleate (C18:2), and linolenate (C18:3). Microalgal diversity analyses determined the presence of Chlorella, Scenedesmus, and Stigeoclonium as the dominant microalgae. The algal consortium provides significant value not only in terms of energy savings and nutrient removal but also because of its bioenergy potential as indicated by the lipid content (20-23%) and FAME profiling.