• ALGAE
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• 제20권4호
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• pp.295-298
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• 2005

The growth of subaerial microalgae on historic buildings or various cultural properties causes discoloration and physico-chemical deterioration of the surfaces. We collected a subaerial chlorophyte, Chlorella sp., from the stone Standing Buddha statue at Jungwon Miruksazi, which is a national treasure of Korea, and found dormant, thickwalled spores with regular pentagonal ornamentation along with the vegetative Chlorella cells. The morphology of Chlorella resting spores was compared to that of the other green algal resting cells. The ornamented spores and smooth-walled vegetative cells revived in 2 weeks in a liquid freshwater medium and started reproduction by autospores. To our knowledge, the ability of Chlorella to form ornamented dormant spores in drought condition was not previously recorded. The ornamentation of spores would supplement taxonomic characteristics of this genus.

• KSBB Journal
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• 제15권6호
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• pp.644-648
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• 2000

Biological fixation of carbon dioxide using microalgae is known as an effective CO$_2$reduction technology. However, many environmental factors influence microalgal productivity. Optimal cultivation factors were determined for the green alga, Euglena gracilis Z, which offers high protein and vitamin E content for animal fodder. In batch culture in a photovioreactor, it was found that theinitial pH, temperature, CO$_2$concentration in air, and light intensity during the optimal cultivating conditions were 3.5, 27$^{\circ}C$, 5-10% and 520 ${\mu}$mol/㎡/s, respectively. When tap water and freshwater were used as cultivating media unsterilized tap water was found to be effective. A kinetic model was considered to determine the relationship between the specific growth rate and the light intensity. The half-velocity coefficient (K(sub)I) in the Monod model under photoautotrophic conditions was 978.9 ${\mu}$mol/㎡/s.

• Journal of Species Research
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• 제12권4호
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• pp.313-320
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• 2023

Diatoms are unicellular eukaryotic microalgae, and they are highly diversified in aquatic environments. We describe an unrecorded diatom species Fragilaria saxoplanctonica Lange-Bertalot & Ulrich (Bacillariophyceae) collected from Paldang Reservoir, Korea, on 4 April 2022. The valve was needle shaped and narrowly rectangular, its ends were rounded, and no spines were found on the outline of their valves. The valve was 67.2-70.2㎛ in length and 1.4-2.9㎛ in width. The ratio of width-to-length was 1 : 23.2-50.1. The pattern of striation was alternate or opposite, and the number of striae in 10㎛ was 24-26. Molecular comparisons of the 18S rDNA and rbcL sequences showed that it belonged to the genus Fragilaria. These morphological and phylogenetic results confirmed that our species was F. saxoplanctonica, and it was the first record in Korea.

• ALGAE
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• 제31권2호
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• pp.155-165
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• 2016

Green microalgae from the class Chlorophyceae represent a major biodiversity component of eukaryotic algae in continental water. Identification and classification of this group through morphology is a hard task, since it may present cryptic species and phenotypic plasticity. Despite the increasing use of molecular methods for identification of microorganisms, no single standard barcode marker is yet established for this important group of green microalgae. Some available studies present results with a limited number of chlorophycean genera or using markers that require many different primers for different groups within the class. Thus, we aimed to find a single marker easily amplified and with wide coverage within Chlorophyceae using only one pair of primers. Here, we tested the universality of primers for different genes (tufA, ITS, rbcL, and UCP4) in 22 strains, comprising 18 different species from different orders of Chlorophyceae. The ITS primers sequenced only 3 strains and the UCP primer failed to amplify any strain. We tested two pairs of primers for rbcL and the best pair provided sequences for 10 strains whereas the second one provided sequences for only 7 strains. The pair of primers for the tufA gene presented good results for Chlorophyceae, successfully sequencing 21 strains and recovering the expected phylogeny relationships within the class. Thus, the tufA marker stands out as a good choice to be used as molecular marker for the class.

• KSBB Journal
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• 제27권6호
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• pp.335-340
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• 2012

The microalgae, Microcystis aeruginosa are able to proliferate in a wide range of freshwater ecosystem. M. aeruginosa was cultivated in 25 L and 240 L race-way reactor containing modified medium with added urea 0.2 g/L, increased $Fe^{+2}$, and decreased $Ca^{+2}$ion compared to BG11 medium. Sugar contents of M. aeruginosa grown in BG11 medium, and modified medium were 120 mg/mL and 140 mg/mL respectively. Fermentation was conducted with the extract of M. aeruginosa at $30^{\circ}C$ for 30 h, using Saccharomyces cerevisiae (Sc), Pichia stipitis (Ps), Zymomonas mobilis (Zm), and mixed-culture of these strains (Sc + Ps + Zm). Pichia stipitis (0.7%) was found to be more suitable for producing bioalcohol from M. aeruginosa extract than other strains of Saccharomyces cerevisiae (0.45%) and Zymomonas mobilis (0.61%), while mixed-cultured of these strains showed higest productivity by 1.75%. Biomass of M. aeruginosa contains the potency to be the most renewable resource for bioalcohol fermentation.

• 한국수산과학회지
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• 제43권2호
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• pp.131-138
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• 2010

This study determined the optimum microalgae species and concentration for the brackish water flea, Diaphanosoma celebensis, in individual and community cultures by feeding it several different diets. Six single trials (Tetraselmis suecica, Isochrysis galbana, marine Chlorella ellipsoidea, freshwater Chlorella vulgaris, Scenedesmus sp., Selenastrum sp.) were conducted at 10 psu and $30^{\circ}C$. The community and individual cultures of the water flea were performed in 1-L beakers and 3-mL vessels (12-well culture plates), respectively. In the community cultures, the maximum density and specific growth rate were highest for water fleas fed T. suecica, reaching 60.0 individuals (ind.)/mL and 0.40, respectively. In the individual cultures, the most offspring and greatest life span of females were 56.9 ind. and 24.3 days, respectively, in the T. suecica trial. By contrast, diets of Scenedesmus sp. and Selenastrum sp. resulted in poor growth rates. In the T. suecica experiments examining a range of 10 to $200\times10^3$ cells/indl. the specific growth rate of the water flea tended to increase with the amount of supplement, while the life span decreased. The maximum density and number of offspring of females was highest at 53.5 ind./mL and 38.8 ind. respectively, at 40,000 cells/ind. These results suggest that the best microalgae species for the mass culture of D. celebensis is T. suecica and the optimum concentration is 40,000 cells per individual.

• Journal of Microbiology and Biotechnology
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• 제27권6호
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• pp.1112-1119
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• 2017

The aim of this study was to develop a potential process for bioethanol production from Hydrodictyon reticulatum (HR), a filamentous freshwater alga, using Saccharomyces cerevisiae (KCTC7017). From the sugar solutions prepared by the four different hydrolysis methods, bioethanol production ranged from 11.0 g/100 g dried material (acid hydrolysis) to 22.3 g/100 g dried material (enzymatic hydrolysis, EH). Bioethanol was fermented from a highly concentrated sugar solution obtained by a decompression-mediated (vacuum) enrichment method (VE). As the results, ethanol was more efficiently produced from HR when sugar solutions were concentrated by VE following EH (EH/VE). Using multiple feeding of the sugar solution prepared by EH/VE from HR, ethanol reached up to a concentration of 54.3 g/l, corresponding to 24.9 g/100 g dried material, which attained the economic level of product concentration (approximately 5%). The results indicate that by using HR, it is feasible to establish a bioethanol production process, which is effective for using microalgae as the raw material for ethanol production.

• Journal of Microbiology and Biotechnology
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• 제23권3호
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• pp.375-381
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• 2013

A freshwater microalga, Chlamydomonas reinhardtii KNUA021, was characterized for its potential as a biochemical feedstock. Its optimal growth was observed when the culture was incubated at $25^{\circ}C$ and pH 9.4. However, the isolate was capable of survival and growth under a variety of temperatures (10-$30^{\circ}C$) and pH (pH 4.0-12.0) conditions. The total lipid content of the isolate was 21.7% of dry weight and it was found that a high-value fatty alcohol, hexadecenol ($C_{20}H_{40}O$), was autotrophically produced by strain KNUA021. In addition, a nutritionally important $C_{18:3}{\omega}3$ (${\alpha}$-linolenic acid, ALA) was also identified in this photosynthetic microorganism as one of the major fatty acids. Hence, C. reinhardtii KNUA021 appears to show promise for use in the production of microalgae-based biochemicals.

• 한국지반환경공학회 논문집
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• 제12권12호
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• pp.31-35
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• 2011

본 연구는 담수미세조류의 일종인 클로렐라를 발광다이오드를 이용하여 효율적으로 배양하기 위한 조건을 찾기 위해 수행되었다. 클로렐라 배양에 최적인 파장을 찾기 위해 청색, 적색, 백색, 그리고 혼합광을 클로렐라가 포함된 반응기에 각각 조사하여 성장속도 및 셀농도를 측정하였다. 적색파장이 클로렐라의 성장에 가장 효율적이었으며, 광량이 증가할수록 성장속도 및 셀농도도 광량에 비례하여 가장 많이 증가하였다. 본 연구를 통해 클로렐라를 효과적으로 배양하기 위해서는 적색파장의 발광다이오드를 광원으로 사용하는 것이 효과적임을 알 수 있었다.

• Ocean and Polar Research
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• 제25권2호
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• pp.213-226
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• 2003

Kongsfjorden near Korean Arctic Station, Dasan, is a glacial fjord in the Svalbard archipelago, Arctic that is influenced by both Atlantic and Arctic water masses. During the Arctic field season August 2002, surface temperature, salinity, density, and phytoplankton biomass (chi a) was measured in Kongsfjorden. A total of 15 surface samples were collected for the phytoplankton related measurements. Chl a values ranged from 0.08 to 1.4mg chi a $m^{-3}$ (mean of 0.53mg chl a $m^{-3}$) in the overall surface stations. The highest values of the chi a concentrations (> 1.0mg chi a $m^{-3}$) were found near glacier in the northeastern part of Kongsfjorden. Nanoplanktonic (< $20{\mu}m$) phytoflagellates were important contributors for the increase of the chi a. The nano-sized phytoflagellates accounted for more than 90% of the total chi a biomass in the study area. Surface temperatures and salinities ranged from 2.5 to $7.18^{\circ}C$ (mean of $4.65^{\circ}C$) and from 22.55 to 32.97 psu (mean of 30.16 psu), respectively. The physical factors were not highly correlated with phytoplankton distribution. The character of surface water due to down-fjord wind was highly similar to phytoplankton distribution. Drifting ice, freshwater, and semdiment inputs from large tidal glaciers located in the inner part of Konsfjorden create steep physico- and biogeochemical environmental gradients along the length of this ford. The glacial inputs cause reduced biodiversity biomass and productivity in the pelagic community in the inner fjord. Primary production of benthic and pelagic microalgae is reduced due to the limited light levels in the turbid and mixed inner waters. The magnitude of glacial effects diminishes towards the outer fjord. Kongsfjorden is an important feeding ground fer marine mammals and seabirds. Especially, seabirds play the largest energy intake and also export nutrients for primary production of the marine microalgae. Kongsfjorden has received a lot of research attention as a site for exploring the impacts of climate changes. Dasan Station in Kongsfjorden will be an important Arctic site for monitoring and detecting future environmental changes.