• Ecology and Resilient Infrastructure
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• v.6 no.1
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• pp.77-77
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• 2019

• Korean Journal of Environmental Agriculture
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• v.34 no.2
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• pp.139-148
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• 2015

BACKGROUND: The aim of this study was to isolate and identify algicidal bacterium that tends to kill the toxic dinoflagellate Alexandrium catenella, and to determine the algicidal activity and algicidal range of algicide. METHODS AND RESULTS: Among of algicidal bacteria isolated in this study, NH-3 isolate was the strongest algicidal activity against A. catenella. NH-3 isolate was identified on the basis of biochemical characteristics and analysis of 16S rRNA gene sequences. The NH-3 isolate showed over 99% homology with Arthrobacter oxydans, and was designated as Arthrobacter sp. NH-3. The optimal culture conditions were $25^{\circ}C$, initial pH 7.0, and 2.0% (w/v) NaCl concentration. The algicidal activity of Arthrobacter sp. NH-3 was significantly increased to maximum value in the late of logarithmic phase. Arthrobacter sp. NH-3 showed algicidal activity through indirect attack, which excreted active substance into the culture filtrate. When 10% culture filtrate of NH-3 was applied to A. catenella, 100% of algal cells were destroyed within 30 h. In addition, the algicidal activities were increased in dose and time dependent manners. The pure algicide was isolated from the ethyl acetate extract of the culture filtrate of NH-3 by using silica gel column chromatography and high performance liquid chromatography (HPLC). We investigated the algicidal activity of this algicide on the growth of harmful algal bloom (HAB) species, including A. catenella. As a result, it showed algicidal activity against several HAB species at a concentration of $100{\mu}g/mL$ and had a relatively wide host range. CONCLUSION: Taken together, our results suggest that Arthrobacter sp. NH-3 and its algicide could be a candidate for controlling of toxic and harmful algal blooms.

• Journal of Environmental Science International
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• v.17 no.4
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• pp.439-449
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• 2008

Algicidal bacterium was isolated from sea water during the declining period of Cochlodinium polykrikoides blooms and this bacterium had a significant algicidal activity against C. polykrikoides. In this study, algicidal bacterium was identified on the basis of biochemical and chemotaxonomic characteristics, and analysis of 16S rDNA sequences. The algicidal bacterium showed 98.6% homology with Micrococcus luteus ATCC $381^T$. Therefore, this bacterium was designated Micrococcus luteus SY-13. The optimal culture conditions of the algicidal bacterium was $25^{\circ}C$, initial pH 8.0, and 3.0% NaCl concentration. M. luteus SY-13 is assumed to produce secondary metabolites which have algicidal activity. When 10% culture filtrate of this strain was applied to C. polykrikoides ($1.0\;{\times}\;10^4\;cells/ml$) cultures, over 98% of C, polykrikoides cells were destroyed within 6 hours. The culture filtrate of M. luteus SY-13 exhibited similar algicidal activity after heat-treatment at $121^{\circ}C$ for 15 min. While algicidal activity remained in filtrates with pH adjusted to 8.0, loss of algicidal activity occurred when the pHs of filtrates were adjusted to over 9.0 or heat-treated at $121{\times}180^{\circ}C$ for 1 hour. M. luteus SY-13 showed significant algicidal activities against C. polykrikoides (98.9%) and a wide algicidal range against various harmful algal bloom (HAB) species. However, there was no algicidal effect on diatom and marine livefood organisms except Isocrysis galbana. These results suggest that M. luteus SY-13 could be a candidate for use in the control of HABs.

• KSBB Journal
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• v.26 no.1
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• pp.7-12
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• 2011

In order to perform an acute toxicity assessment of a new algicide, thiazolidinedione derivative (TD53) with enhanced solubility and lower toxicity to marine ecosystem, representative 3 organisms: plant plankton (Skeletonema costatum), animal plankton (Daphnia magna), fish (Paralichthys olivaceus) related in the food chain of marine ecosystem according to OECD standard methods were employed in the exposure experiment. The exposure assessment showed that $EC_50$ of S. costatum in 96-hour, $EC_50$ of D. magna in 48-hour and $LC_50$ of P. olivaceus in 72-hour for TD53 were $1.53\;{\mu}M$, $0.61\;{\mu}M$ and $2.14\;{\mu}M$ respectively. NOEC (No Observed Effect Concentration) and PNEC (Predicted No Effect Concentration) were calculated to be $0.25\;{\mu}M$ and 6.10 nM, respectively from $EC_50$ of most sensitive strain, D. magna. Comparing with the results of toxicity assessment previously performed by using Ulva pertusa Kjellman accepted as an ISO standard method, the values of PNEC showed 3.7 times lower toxicity in case of this study employing 3 organisms, indicating that if the organisms which are more representative and sensitive in marine ecosystem are further investigated, more accurately and validly predicted toxicity of TD53 could be applied in field.

• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.176-186
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• 2016

For several decades, lactic acid bacterium (Lactobacillus graminis: LAB) has been generally recognized as safe. To develop the pan-environmental bio-control agent, algicidal activity of the live LAB cell and its culture filtrate (CF) was examined against Microcystis aeruginosa. LAB cells perfectly lysed M. aeruginosa within 3 days, while the CF had a less effect than the live cells, approximately 78% inhibition of algal growth during a same culture period. The concentration of microcystin in alone culture of M. aeruginosa was $7.1{\mu}gL^{-1}$, but gradually increased and leach $158.5{\mu}gL^{-1}$ on 10 days. However, LAB cells clearly decreased the microcystin by $10.3{\mu}gL^{-1}$ in the same period, approximately 93.5%. CF of LAB showed a strong algicidal activity over 75% between pH 2-7, 91.3% by the treatment of proteinase K, 87.8% by below 3 kDa in particle size, and 75.3% by heat treatment, respectively. Of five solvents, fractions of CF passed through solvents diethyl ether and ethyl acetate showed an obvious algicidal activity in the algal-lawn test. Among 5 fractions purified by silica-gel TLC plate, two spots showed a most strong removal activity on M. aeruginosa. Another analysis of GC indicate that CF contained six representative fatty acids. Even though most of these substance have been known as an anti-algal substance against M. aeruginosa, oleic acid is the most effective. These results suggested that the culture filtrate or specific substances, like a fatty acids, in comparison with live L. graminis can be a successful and eco-friendly agent to control Microcystis bloom.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.261-270
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• 2005

Biological control agents (BCA; algicidal bacterium Xantobacter autotrophycus) plus casitone media, strongly changed physicochemical variables, standing crops of phytoplankton and microcystin-LR phytoplankton in 100-L mesocosm constructed in a small hexagonal pond (3.5 m ${\times}$ 5 m). No M. aeruginosa showed by 8 days, and 60% of total standing crops of phytoplanktons were decreased by the BCA treatment. BCA treatment also induced a strong decline of cellular extracted microcystin-LR (MCLR) and a remarkable increase of dissolved MCLR with the decrement in standing crops of cyanobacteria. In addition, BCA strongly increased all nutrients, but new outbreak of phytoplanktons hardly showed in the experimental mesocosm. The field application of BCA to controling the cyanobacterial bloom in large lakes and reservoirs is not relevant due to high concentration of nutrients and toxins. Thus, a further study is needed to diminish the adverse effects after BCA treatment for water quality preservation.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.475-481
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• 2005

In an effort to identify a new environment-friendly algicide, we examined the ability of extracts from the leaves and stems of nine Korean oak tree species to inhibit growth of the bloom-forming cyanobacterium, Microcystis aeruginosa. At a concentration of 100 mg $L^{-1}$, five of the oak tree extracts (QAT-L, QAT-5, QAS- L, QGI-5, and QSA- L) decreased the cell density of M. aeruginosa by over 90% for 7 days. At a concentration of 20 mg $L^{-1}$, the same five extracts inhibited the growth of M. aeruginosa by approximately 50%. The minimum concentration of oak tree extracts required for effective inhibition of M. aeruginosa (20 mg $L^{-1}$) is comparable to that of the known algicide, tannic acid (17 mg $L^{-1}$), which is thought to be one of the main active ingredients in the oak tree extract. These findings suggest that oak extracts may be useful as an environment-friendly algicide to control the bloomforming cyanobacterium, M. aeruginosa, in eutrophic waters.

• KSBB Journal
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• v.25 no.6
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• pp.527-532
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• 2010

A thiazolidinedione derivative, TD49 with the highly selective algicide to red tide was newly synthesized and its acute toxicity was examined in order to evaluate the effect on aquatic ecosystems of coast. Major three species having important role in the food chain of marine ecosystem, such as Skeletonema costatum of microalgae, Daphnia magna of crustacea, Paralichthys olivaceus of flatfish fingerling were employed for the acute toxicity assessment. $EC_50$ or $LC_50$ as the assessment criterion was investigated to each specie, and NOEC (No Observed Effect Concentration) and PNEC (Predicted No Effect Concentration) from most sensitive specie to toxicity of TD49 were further calculated. $EC_50$ of S. costatum in 96-hour, $EC_50$ of D. magna in 48-hour, and $LC_50$ of P. olivaceus in 72-hour for TD49 were $0.34\;{\mu}M$, $0.68\;{\mu}M$, and $0.58\;{\mu}M$, respectively. NOEC from the results of S. costatum was estimated to be $0.20\;{\mu}M$ and PNEC was estimated as 3.40 nM by applying factor value of 100 to $EC_50$ $0.34\;{\mu}M$ of S. costatum. In addition, it was revealed that Solutol used as the dispersing agent of TD49 had very little toxic influence under the concentration range of $0{\sim}0.4\;{\mu}M$ used in TD49 toxicity experiment. Although the estimated concentration of TD49 that will be sprayed onto the coastal field for the algicide is higher than NOEC value, it is considered that the spraying concentration would not be a considerable problem due to a dilution effect by tide at the opened coast.