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Dr. Chi-Yong Ahn
Korea Research Institute of Bioscience and Biotechnology (KRIBB), South Korea

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0 Cyanobacteria
0 microalgae
0 dinoflagellate
0 red tide
0 Harmful algal bloom (HAB)

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Cyanobacteria
microalgae
dinoflagellate
Harmful algal bloom (HAB)

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Journal article
Published: 17 June 2021 in Applied Sciences
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In recent decades, harmful algal blooms (HABs) have been significantly affecting environments, aquatic ecosystems, and human health, as well as damaging economies, especially near rivers and lakes, and in coastal regions. Microcystis and Anabaena are two genera of harmful cyanobacteria that will often predominate during toxic microalgal blooms. In this study, we employ a method for control and mitigation of HABs by microalgal cell instability using different types of aminoclays (ACs). Allelopathic interactions between the two strains of algae are studied in mono-culture, co-culture, and filtrated cell-free medium in the presence of the ACs. The growth of the Anabaena strain is significantly reduced by the cyanobacterial strains in the co-culture media, and both are significantly affected by the Acs’-enhanced algicidal activity. Anabaena sp. KVSF7 shows higher sensitivity against the ACs than does Microcystis sp. KW. In this way, the algicidal activity of ACs is harnessed, the effects of which are in the order of aluminum aminoclay (AlAC) > magnesium aminoclay (MgAC) > calcium aminoclay (CaAC). The ammonium sites in the ACs carry positive charges to induce instability of HABs along with the electrostatic attraction between algal cells and AC. Therefore, the utilization of the algicidal activity of the ACs can effectively reduce HABs, especially on cyanobacterial blooms.

ACS Style

Minh Nguyen; Vu Bui; Chi-Yong Ahn; Hee-Mock Oh; Jin-Soo Koh; Ju-Young Moon; Young-Chul Lee. Loading Effects of Aminoclays in Co-Culture of Two Cyanobacterial Microcystis and Anabaena Species as an Algicidal Role. Applied Sciences 2021, 11, 5607 .

AMA Style

Minh Nguyen, Vu Bui, Chi-Yong Ahn, Hee-Mock Oh, Jin-Soo Koh, Ju-Young Moon, Young-Chul Lee. Loading Effects of Aminoclays in Co-Culture of Two Cyanobacterial Microcystis and Anabaena Species as an Algicidal Role. Applied Sciences. 2021; 11 (12):5607.

Chicago/Turabian Style

Minh Nguyen; Vu Bui; Chi-Yong Ahn; Hee-Mock Oh; Jin-Soo Koh; Ju-Young Moon; Young-Chul Lee. 2021. "Loading Effects of Aminoclays in Co-Culture of Two Cyanobacterial Microcystis and Anabaena Species as an Algicidal Role." Applied Sciences 11, no. 12: 5607.

Journal article
Published: 20 April 2021 in Science of The Total Environment
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Microbes interact with each other in response to various environmental changes in coastal marine ecosystems. To explore how the macroenvironment (environmental filtering) and species-engineered microenvironment (niche construction) affect the ecological network of the marine microbiome in the highly dynamic coastal waters of Korea, we analyzed the modular structures of the microbial community and identified microbial interconnections in different size fractions for a year. Fluctuations in the macroenvironment, such as temperature and nutrient concentrations driven by seasonal changes, are the major factors in determining successive microbial modules. Compared to particle-associated (PA) microbes, free-living (FL) microbes seemed to be more affected by macroenvironmental filtering. Modules related to nutrients were further divided into various modules according to different lifestyles. In addition, a large transient discharge of the Changjiang (Yangtze River) in summer also formed a distinct microbial module, which was related to the high ammonia concentration arising from phytoplankton degradation. Microbes belonging to the SAR11, SAR86, and SAR116 clades, Flavobacteriaceae, and MG IIa-L showed repeated interconnections in temperature-related modules, while the SAR202 clade, Marinimicrobia, DEV007 clade, and Arctic97B-4 and Sva0996 marine groups displayed repeated connections in nutrient-related modules. These ‘skeleton’-forming microbes created species-engineered microenvironments, further fine-tuning microbial modular structures. Furthermore, they serve as keystone species for module stability by linking interdependent microbial partners within their own modules through universally beneficial metabolic activities. Therefore, they could reinforce the ecological resilience of microbial communities under abiotic and biotic perturbations in dynamic coastal waters. In conclusion, both macro- and micro-environmental filtering were important for determining the seasonal succession of microbial community structures.

ACS Style

Seong-Jun Chun; Yingshun Cui; Seung Ho Baek; Chi-Yong Ahn; Hee-Mock Oh. Seasonal succession of microbes in different size-fractions and their modular structures determined by both macro- and micro-environmental filtering in dynamic coastal waters. Science of The Total Environment 2021, 784, 147046 .

AMA Style

Seong-Jun Chun, Yingshun Cui, Seung Ho Baek, Chi-Yong Ahn, Hee-Mock Oh. Seasonal succession of microbes in different size-fractions and their modular structures determined by both macro- and micro-environmental filtering in dynamic coastal waters. Science of The Total Environment. 2021; 784 ():147046.

Chicago/Turabian Style

Seong-Jun Chun; Yingshun Cui; Seung Ho Baek; Chi-Yong Ahn; Hee-Mock Oh. 2021. "Seasonal succession of microbes in different size-fractions and their modular structures determined by both macro- and micro-environmental filtering in dynamic coastal waters." Science of The Total Environment 784, no. : 147046.

Journal article
Published: 30 March 2021 in Bioresource Technology
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Microalgal treatment of undiluted raw piggery wastewater is challenging due to ammonia toxicity and a deep dark color hampering photosynthesis. To overcome these problems, (1) a microalga (Coelastrella sp.) was isolated from an ammonia-rich environment, (2) the wastewater treatment was divided into two steps: a heterotrophic process followed by a mixotrophic process, and (3) a narrower transparent photobioreactor was employed with higher light intensity in the mixotrophic process. Coelastrella sp. removed 99% of ammonia, 92% of chemical oxygen demand (COD), and 100% of phosphorus during the 4-day process. Acetate in the wastewater relieved the ammonia stress on microalgae and promoted algal lipid and triacylglycerol productivity. Oxidative stability and low-temperature fluidity of triacylglycerols in lipids were improved by means of an altered fatty acid profile. Aside from the overall microalgal treatment performance, the proposed processing of piggery wastewater yielded a material suitable for possible production of algal biodiesel of better quality.

ACS Style

Sang-Ah Lee; So-Ra Ko; Nakyeong Lee; Jun-Woo Lee; Ve Van Le; Hee-Mock Oh; Chi-Yong Ahn. Two-step microalgal (Coelastrella sp.) treatment of raw piggery wastewater resulting in higher lipid and triacylglycerol levels for possible production of higher-quality biodiesel. Bioresource Technology 2021, 332, 125081 .

AMA Style

Sang-Ah Lee, So-Ra Ko, Nakyeong Lee, Jun-Woo Lee, Ve Van Le, Hee-Mock Oh, Chi-Yong Ahn. Two-step microalgal (Coelastrella sp.) treatment of raw piggery wastewater resulting in higher lipid and triacylglycerol levels for possible production of higher-quality biodiesel. Bioresource Technology. 2021; 332 ():125081.

Chicago/Turabian Style

Sang-Ah Lee; So-Ra Ko; Nakyeong Lee; Jun-Woo Lee; Ve Van Le; Hee-Mock Oh; Chi-Yong Ahn. 2021. "Two-step microalgal (Coelastrella sp.) treatment of raw piggery wastewater resulting in higher lipid and triacylglycerol levels for possible production of higher-quality biodiesel." Bioresource Technology 332, no. : 125081.

Journal article
Published: 01 December 2020 in International Journal of Systematic and Evolutionary Microbiology
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A novel Gram-stain-negative, aerobic, non-spore-forming, non-motile, and rod-shaped bacterium, strain ETT8T was isolated from a chemostat culture of microalga Ettlia sp. YC001. Optimal growth was with 0–2% NaCl and at 25–37 °C on R2A medium. Phylogenetic analysis based on the 16S rRNA gene and genome sequence showed that strain ETT8T belongs to the genus Tabrizicola , with the close neighbours being T. sediminis DRYC-M-16T (98.1 %), T. alkalilacus DJCT (97.6 %), T. fusiformis SY72T (96.9 %), T. piscis K13M18T (96.8 %), and T. aquatica RCRI19T (96.5 %). The genomic comparison of strain ETT8T with type species in the genus Tabrizicola was analysed using the genome-to-genome distance calculator (GGDC), average nucleotide identity (ANI), and average amino acid identity (AAI) (values indicated ≤17.7, ≤75.4 and ≤71.9 %, respectively). The genomic DNA G+C content of strain ETT8T was 64.4 %, plus C18 : 1 ω6c and C18 : 0-iso were the major fatty acids and Q-10 the major respiratory quinone. Strain ETT8T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine aminolipid, and four unidentified lipids as the major polar lipids. Based on the chemotaxonomic, genotypic, and phenotype results, strain ETT8T was recognized as a novel species of the genus Tabrizicola for which the name Tabrizicola algicola sp. nov. is proposed. The type strain is ETT8T (=KCTC 72206T=JCM 31893T=MCC 4339T).

ACS Style

Chan-Yeong Park; Seong-Jun Chun; Chunzhi Jin; Ve Van Le; Yingshun Cui; Song-Yeon Kim; Chi-Yong Ahn; Hee-Mock Oh. Tabrizicola algicola sp. nov. isolated from culture of microalga Ettlia sp. International Journal of Systematic and Evolutionary Microbiology 2020, 70, 6133 -6141.

AMA Style

Chan-Yeong Park, Seong-Jun Chun, Chunzhi Jin, Ve Van Le, Yingshun Cui, Song-Yeon Kim, Chi-Yong Ahn, Hee-Mock Oh. Tabrizicola algicola sp. nov. isolated from culture of microalga Ettlia sp. International Journal of Systematic and Evolutionary Microbiology. 2020; 70 (12):6133-6141.

Chicago/Turabian Style

Chan-Yeong Park; Seong-Jun Chun; Chunzhi Jin; Ve Van Le; Yingshun Cui; Song-Yeon Kim; Chi-Yong Ahn; Hee-Mock Oh. 2020. "Tabrizicola algicola sp. nov. isolated from culture of microalga Ettlia sp." International Journal of Systematic and Evolutionary Microbiology 70, no. 12: 6133-6141.

Journal article
Published: 01 November 2020 in International Journal of Systematic and Evolutionary Microbiology
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A novel Gram-stain-negative, aerobic, and rod-shaped bacterial strain, M24A2MT, was isolated from seawater in the Republic of Korea. On the basis of the 16S rRNA gene phylogeny, strain M24A2MT was found to be closely related to Novosphingobium pentaromativorans US6-1T and Novosphingobium mathurense SM117T with pair-wise sequence similarities of 97.4 and 96.9 %, respectively. Phylogenetic analysis of 16S rRNA sequences indicated that M24A2MT formed a branch with Novosphingobium pentaromativorans US6-1T and represented a member of the genus Novosphingobium . The predominant cellular fatty acids were C14 : 0 2-OH, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The polar lipids of strain M24A2MT consisted mainly of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, one unidentified phospholipid, and two unidentified lipids. The respiratory quinone was ubiquinone Q-10. The genomic DNA G+C content was 63.9 %. Given the phenotypic characteristics along with the phylogenetic distinctness and chemotaxonomic features, strain M24A2MT is considered to represent a novel species within the genus Novosphingobium , for which the name Novosphingobium aquimarinum sp. nov. is proposed. The type strain of Novosphingobium aquimarinum sp. nov. is M24A2MT (=KCTC 72894T=JCM 33983T).

ACS Style

Ve Van Le; So-Ra Ko; Sang-Ah Lee; Long Jin; Chi-Yong Ahn; Hee-Mock Oh. Novosphingobium aquimarinum sp. nov., isolated from seawater. International Journal of Systematic and Evolutionary Microbiology 2020, 70, 5911 -5917.

AMA Style

Ve Van Le, So-Ra Ko, Sang-Ah Lee, Long Jin, Chi-Yong Ahn, Hee-Mock Oh. Novosphingobium aquimarinum sp. nov., isolated from seawater. International Journal of Systematic and Evolutionary Microbiology. 2020; 70 (11):5911-5917.

Chicago/Turabian Style

Ve Van Le; So-Ra Ko; Sang-Ah Lee; Long Jin; Chi-Yong Ahn; Hee-Mock Oh. 2020. "Novosphingobium aquimarinum sp. nov., isolated from seawater." International Journal of Systematic and Evolutionary Microbiology 70, no. 11: 5911-5917.

Journal article
Published: 10 August 2020 in Chemosphere
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A high ammonia concentration and chemical oxygen demand (COD) in piggery wastewater force it to be diluted before conventional microalgal treatment to reduce ammonia toxicity. Incomplete treatment of ammonia and COD in piggery wastewater may cause eutrophication, resulting in algal blooms. This study tried to treat raw piggery wastewater without dilution, using three strains of microalgae (Chlorella sorokiniana, Coelastrella sp. and Acutodesmus nygaardii) that outcompeted other algae under heterotrophic, mixotrophic, and autotrophic conditions, respectively, through adaptive evolution at high ammonia concentration. The three stepwise processes were designed to remove (1) small particles, COD, and phosphorus in the 1st heterotrophic C. sorokiniana cultivation, (2) ammonia and COD in the 2nd mixotrophic Coelastrella sp. cultivation, and (3) the remaining ammonia in the 3rd photoautotrophic A. nygaardii cultivation. To enhance ammonia uptake rate, each algal species were inoculated after 2-day nitrogen starvation. When the N-starved three species were inoculated at each step sequentially at 7 g/L for 2 days, the final phosphorus, COD, and ammonia removal efficiencies were 100% (16.4–0 mg/L), 92% (6820–545 mg/L), 90% (850–81 mg/L) and turbidity (99%) after total 6 days.

ACS Style

Sang-Ah Lee; Nakyeong Lee; Hee-Mock Oh; Chi-Yong Ahn. Stepwise treatment of undiluted raw piggery wastewater, using three microalgal species adapted to high ammonia. Chemosphere 2020, 263, 127934 .

AMA Style

Sang-Ah Lee, Nakyeong Lee, Hee-Mock Oh, Chi-Yong Ahn. Stepwise treatment of undiluted raw piggery wastewater, using three microalgal species adapted to high ammonia. Chemosphere. 2020; 263 ():127934.

Chicago/Turabian Style

Sang-Ah Lee; Nakyeong Lee; Hee-Mock Oh; Chi-Yong Ahn. 2020. "Stepwise treatment of undiluted raw piggery wastewater, using three microalgal species adapted to high ammonia." Chemosphere 263, no. : 127934.

Journal article
Published: 01 August 2020 in International Journal of Systematic and Evolutionary Microbiology
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A novel non-phototrophic member of the genus Rhodoferax was obtained from freshwater. The purpose of this study was to analyse the genome of a nonphototrophic strain and propose a new species based on its phylogenetic, genomic, physiological and chemotaxonomic characteristics. The results of phylogenetic analysis based on 16S rRNA gene sequences supports that the strain, designated Gr-4T, has a close relationship to the genus Rhodoferax . The observed average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain Gr-4T and its closest related strains were 72.3–74.6 % and 21.9–22.8 %, respectively. These values were much lower than the species separation thresholds for ANI or dDDH of 95–96 and 70 %, respectively, and in fact fall in the intergeneric range. Strain Gr-4T does not contain RuBisCO-related genes, but does contain GS/GOGAT pathway-related genes enabling nitrate ammonification. A polyphasic study and a genomic-level investigation were done to establish the taxonomic status of strain Gr-4T. Based on the phylogenetic, genomic and physiological differences, it is proposed that the isolate be classified to the genus Rhodoferax as Rhodoferax aquaticus sp. nov. with isolate Gr-4T (=KCTC 32394T=JCM 19166T) as the type strain.

ACS Style

Taihua Li; Ye Zhuo; Chun-Zhi Jin; Xuewen Wu; So-Ra Ko; Feng-Jie Jin; Chi-Yong Ahn; Hee-Mock Oh; Hyung-Gwan Lee; Long Jin. Genomic insights into a novel species Rhodoferax aquaticus sp. nov., isolated from freshwater. International Journal of Systematic and Evolutionary Microbiology 2020, 70, 1 .

AMA Style

Taihua Li, Ye Zhuo, Chun-Zhi Jin, Xuewen Wu, So-Ra Ko, Feng-Jie Jin, Chi-Yong Ahn, Hee-Mock Oh, Hyung-Gwan Lee, Long Jin. Genomic insights into a novel species Rhodoferax aquaticus sp. nov., isolated from freshwater. International Journal of Systematic and Evolutionary Microbiology. 2020; 70 (8):1.

Chicago/Turabian Style

Taihua Li; Ye Zhuo; Chun-Zhi Jin; Xuewen Wu; So-Ra Ko; Feng-Jie Jin; Chi-Yong Ahn; Hee-Mock Oh; Hyung-Gwan Lee; Long Jin. 2020. "Genomic insights into a novel species Rhodoferax aquaticus sp. nov., isolated from freshwater." International Journal of Systematic and Evolutionary Microbiology 70, no. 8: 1.

Journal article
Published: 12 June 2020 in Toxins
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Blooms of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides are responsible for massive fish mortality events in Korean coastal waters (KCW). They have been consistently present in southern KCW over the last two decades, but they were not observed in 2016, unlike in the previous years. Despite extensive studies, the cause of this absence of this dinoflagellate bloom remains largely unknown. Thus, we compared physico-chemical and biological data from along the Tongyeong coast between 2016 and the previous four years (2012–2015). The averages of water temperature and salinity in August, 2016 were significantly (p < 0.001) different from those in the previous years. The amount of Changjiang River discharge, which can affect the environmental conditions in the southern Korean coastal area via ocean currents, was larger than in the previous years, resulting in a reduction in the salinity level in August when blooms of C. polykrikoides usually occurred. Moreover, compared to previous years, in 2016, there was a weak expansion of C. polykrikoides blooms in the Goheung-Oenarodo area where C. polykrikoides blooms were annually initiated in KCW. Lastly, the strong winds from the typhoon Lionrock may also have contributed to the early termination of this dinoflagellate bloom. Together with these findings, the combination of these environmental conditions in 2016, unlike in previous years, may have inhibited the formation of C. polykrikoides blooms along the Tongyeong coast.

ACS Style

Seung Ho Baek; Yunji Kim; Minji Lee; Chi-Yong Ahn; Kyung Hwa Cho; Bum Soo Park. Potential Cause of Decrease in Bloom Events of the Harmful Dinoflagellate Cochlodinium polykrikoides in Southern Korean Coastal Waters in 2016. Toxins 2020, 12, 1 .

AMA Style

Seung Ho Baek, Yunji Kim, Minji Lee, Chi-Yong Ahn, Kyung Hwa Cho, Bum Soo Park. Potential Cause of Decrease in Bloom Events of the Harmful Dinoflagellate Cochlodinium polykrikoides in Southern Korean Coastal Waters in 2016. Toxins. 2020; 12 (6):1.

Chicago/Turabian Style

Seung Ho Baek; Yunji Kim; Minji Lee; Chi-Yong Ahn; Kyung Hwa Cho; Bum Soo Park. 2020. "Potential Cause of Decrease in Bloom Events of the Harmful Dinoflagellate Cochlodinium polykrikoides in Southern Korean Coastal Waters in 2016." Toxins 12, no. 6: 1.

Erratum
Published: 29 April 2020 in Water Research
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ACS Style

Seong-Jun Chun; Yingshun Cui; Jay Jung Lee; In-Chan Choi; Hee-Mock Oh; Chi-Yong Ahn. Corrigendum to “Network analysis reveals succession of Microcystis genotypes accompanying distinctive microbial modules with recurrent patterns” [Water Res. 170 (2020) 115326]. Water Research 2020, 177, 115869 .

AMA Style

Seong-Jun Chun, Yingshun Cui, Jay Jung Lee, In-Chan Choi, Hee-Mock Oh, Chi-Yong Ahn. Corrigendum to “Network analysis reveals succession of Microcystis genotypes accompanying distinctive microbial modules with recurrent patterns” [Water Res. 170 (2020) 115326]. Water Research. 2020; 177 ():115869.

Chicago/Turabian Style

Seong-Jun Chun; Yingshun Cui; Jay Jung Lee; In-Chan Choi; Hee-Mock Oh; Chi-Yong Ahn. 2020. "Corrigendum to “Network analysis reveals succession of Microcystis genotypes accompanying distinctive microbial modules with recurrent patterns” [Water Res. 170 (2020) 115326]." Water Research 177, no. : 115869.

Journal article
Published: 06 March 2020 in Science of The Total Environment
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Harmful algal blooms (HABs) of Cochlodinium (aka Margalefidinium) polykrikoides cause huge economic and ecological damages and thus are considered environmental problems. Previous studies uncovered that the formation and collapse of phytoplankton blooms could be closely related to their associated microbes although their roles in C. polykrikoides bloom have not been elucidated yet. To explore the potential interactions between C. polykrikoides and other microbes (archaea, bacteria, and phytoplankton), we collected water samples in the free-living (FL) (0.22 to 3 μm), nanoparticle-associated (NP) (3 to 20 μm), and microparticle-associated (MP) (>20 μm) fractions when C. polykrikoides blooms occurred from July to August in 2016, 2017, and 2018 in the South Sea of Korea. The microbial composition of the C. polykrikoides-associated microbial cluster (Module I) significantly differed from those of other modules associated with Alexandrium, Chaetoceros or Chattonella. Over half of the interspecies interactions in Module I occurred within the module. That is, specific microbial clusters were associated with the C. polykrikoides bloom. Structural equation modeling (SEM) further confirmed the stronger effects of Module I on C. polykrikoides blooms compared to environmental factors. Among the operational taxonomic units (OTUs) directly correlated with C. polykrikoides, Marine Group I was presumed to supply vitamin B12, the essential element for C. polykrikoides growth, while the potential fish pathogens (Micrococcaceae and Piscirickettsiaceae) could contribute to the massive fish death together with C. polykrikoides itself. In addition, the zoospores of Syndiniales, a parasitoid to dinoflagellates, might be related to the sudden collapse of C. polykrikoides blooms. These microbial groups also contributed to significant alterations of the local microbial community structures. Collectively, network analysis and SEM revealed that the C. polykrikoides bloom is concomitant with distinct microbial communities, contributing to the rise and fall of the bloom, and finally determining the local microbial community structures.

ACS Style

Yingshun Cui; Seong-Jun Chun; Sang-Soo Baek; Seung Ho Baek; Pyoung-Joong Kim; Moonho Son; Kyung Hwa Cho; Chi-Yong Ahn; Hee-Mock Oh. Unique microbial module regulates the harmful algal bloom (Cochlodinium polykrikoides) and shifts the microbial community along the Southern Coast of Korea. Science of The Total Environment 2020, 721, 137725 .

AMA Style

Yingshun Cui, Seong-Jun Chun, Sang-Soo Baek, Seung Ho Baek, Pyoung-Joong Kim, Moonho Son, Kyung Hwa Cho, Chi-Yong Ahn, Hee-Mock Oh. Unique microbial module regulates the harmful algal bloom (Cochlodinium polykrikoides) and shifts the microbial community along the Southern Coast of Korea. Science of The Total Environment. 2020; 721 ():137725.

Chicago/Turabian Style

Yingshun Cui; Seong-Jun Chun; Sang-Soo Baek; Seung Ho Baek; Pyoung-Joong Kim; Moonho Son; Kyung Hwa Cho; Chi-Yong Ahn; Hee-Mock Oh. 2020. "Unique microbial module regulates the harmful algal bloom (Cochlodinium polykrikoides) and shifts the microbial community along the Southern Coast of Korea." Science of The Total Environment 721, no. : 137725.

Journal article
Published: 15 February 2020 in Microorganisms
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This genus contains both phototrophs and nonphototrophic members. Here, we present a high-quality complete genome of the strain CHu59-6-5T, isolated from a freshwater sediment. The circular chromosome (4.39 Mbp) of the strain CHu59-6-5T has 64.4% G+C content and contains 4240 genes, of which a total of 3918 genes (92.4%) were functionally assigned to the COG (clusters of orthologous groups) database. Functional genes for denitrification (narGHJI, nirK and qnor) were identified on the genomes of the strain CHu59-6-5T, except for N2O reductase (nos) genes for the final step of denitrification. Genes (soxBXAZY) for encoding sulfur oxidation proteins were identified, and the FSD and soxF genes encoding the monomeric flavoproteins which have sulfide dehydrogenase activities were also detected. Lastly, genes for the assembly of two different RND (resistance-nodulation division) type efflux systems and one ABC (ATP-binding cassette) type efflux system were identified in the Rhodoferax sediminis CHu59-6-5T. Phylogenetic analysis based on 16S rRNA sequences and Average Nucleotide Identities (ANI) support the idea that the strain CHu59-6-5T has a close relationship to the genus Rhodoferax. A polyphasic study was done to establish the taxonomic status of the strain CHu59-6-5T. Based on these data, we proposed that the isolate be classified to the genus Rhodoferax as Rhodoferax sediminis sp. nov. with isolate CHu59-6-5T.

ACS Style

Chun-Zhi Jin; Ye Zhuo; Xuewen Wu; So-Ra Ko; Taihua Li; Feng-Jie Jin; Chi-Yong Ahn; Hee-Mock Oh; Hyung-Gwan Lee; Long Jin. Genomic and Metabolic Insights into Denitrification, Sulfur Oxidation, and Multidrug Efflux Pump Mechanisms in the Bacterium Rhodoferax sediminis sp. nov. Microorganisms 2020, 8, 262 .

AMA Style

Chun-Zhi Jin, Ye Zhuo, Xuewen Wu, So-Ra Ko, Taihua Li, Feng-Jie Jin, Chi-Yong Ahn, Hee-Mock Oh, Hyung-Gwan Lee, Long Jin. Genomic and Metabolic Insights into Denitrification, Sulfur Oxidation, and Multidrug Efflux Pump Mechanisms in the Bacterium Rhodoferax sediminis sp. nov. Microorganisms. 2020; 8 (2):262.

Chicago/Turabian Style

Chun-Zhi Jin; Ye Zhuo; Xuewen Wu; So-Ra Ko; Taihua Li; Feng-Jie Jin; Chi-Yong Ahn; Hee-Mock Oh; Hyung-Gwan Lee; Long Jin. 2020. "Genomic and Metabolic Insights into Denitrification, Sulfur Oxidation, and Multidrug Efflux Pump Mechanisms in the Bacterium Rhodoferax sediminis sp. nov." Microorganisms 8, no. 2: 262.

Journal article
Published: 01 February 2020 in International Journal of Systematic and Evolutionary Microbiology
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A novel bacterium, strain Seoho-28T, was isolated from a shallow eutrophic lake during the end of cyanobacterial harmful algal blooms and was characterized taxonomically and phylogenetically. Strain Seoho-28T was a Gram-stain-negative, aerobic, rod-shaped and non-motile bacterium. The strain grew optimally with 0 % NaCl and at 25–30 °C on Reasoner's 2A medium. The phylogenetic analysis based on 16S rRNA gene sequences positioned the novel strain among the order Solirubrobacterales , but sequence similarities to known species were less than 94.7 %. The genomic DNA G+C content of the strain Seoho-28T was 74.2 mol%. Genomic comparisons of strain Seoho-28T with families in the order Solirubrobacterales were made using the Genome-to-Genome Distance Calculator, average nucleotide identity and average amino acid identity analyses (values indicated ≤14.9, ≤73.5 and ≤57.8 %, respectively). Strain Seoho-28T contained C16 : 0-iso, C18 : 1 ω9c and C16 : 0 as major fatty acids and MK-7 (H4) as the major quinone. Strain Seoho-28T contained diphosphatidylglycerol, phosphatidylinositol and an unidentified phospholipid as major polar lipids. Meso- and ll-diaminopimelic acids were the diagnostic diamino acids in the cell-wall peptidoglycan. Based on the genotypic, chemotaxonomic and phenotypic results, strain Seoho-28T represents a novel genus and species, Paraconexibacter algicola gen. nov., sp. nov., which belongs to a new family Paraconexibacteraceae in the order Solirubrobacterales and the class Thermoleophilia . The type strain is Seoho-28T (=KCTC 39791T=JCM 31881T).

ACS Style

Seong-Jun Chun; Yingshun Cui; Chunzhi Jin; A Ra Cho; Shu-Kuan Wong; Hyung-Gwan Lee; Hee-Mock Oh; Chi-Yong Ahn. Paraconexibacter algicola gen. nov., sp. nov., a novel actinobacterium isolated from a eutrophic lake during the end of cyanobacterial harmful algal blooms, and proposal of Paraconexibacteraceae fam. nov. in the order Solirubrobacterales. International Journal of Systematic and Evolutionary Microbiology 2020, 70, 915 -922.

AMA Style

Seong-Jun Chun, Yingshun Cui, Chunzhi Jin, A Ra Cho, Shu-Kuan Wong, Hyung-Gwan Lee, Hee-Mock Oh, Chi-Yong Ahn. Paraconexibacter algicola gen. nov., sp. nov., a novel actinobacterium isolated from a eutrophic lake during the end of cyanobacterial harmful algal blooms, and proposal of Paraconexibacteraceae fam. nov. in the order Solirubrobacterales. International Journal of Systematic and Evolutionary Microbiology. 2020; 70 (2):915-922.

Chicago/Turabian Style

Seong-Jun Chun; Yingshun Cui; Chunzhi Jin; A Ra Cho; Shu-Kuan Wong; Hyung-Gwan Lee; Hee-Mock Oh; Chi-Yong Ahn. 2020. "Paraconexibacter algicola gen. nov., sp. nov., a novel actinobacterium isolated from a eutrophic lake during the end of cyanobacterial harmful algal blooms, and proposal of Paraconexibacteraceae fam. nov. in the order Solirubrobacterales." International Journal of Systematic and Evolutionary Microbiology 70, no. 2: 915-922.

Journal article
Published: 07 December 2019 in Water Research
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Every member of the ecological community is connected via a network of vital and complex relationships, called the web of life. To elucidate the ecological network and interactions among producers, consumers, and decomposers in the Daechung Reservoir, Korea, during cyanobacterial harmful algal blooms (cyanoHAB), especially those involving Microcystis, we investigated the diversity and compositions of the cyanobacterial (16S rRNA gene), including the genotypes of Microcystis (cpcBA-IGS gene), non-cyanobacterial (16S), and eukaryotic (18S) communities through high-throughput sequencing. Microcystis blooms were divided into the Summer Major Bloom and Autumn Minor Bloom with different dominant genotypes of Microcystis. Network analysis demonstrated that the modules involved in the different phases of the Microcystis blooms were categorized into the Pre-Bloom, Bloom, Post-Bloom, and Non-Bloom Groups at all sampling stations. In addition, the non-cyanobacterial components of each Group were classified, while the same Group showed similarity across all stations, suggesting that Microcystis and other microbes were highly interdependent and organized into cyanoHAB-related module units. Importantly, the Microcystis genotype-based sub-network uncovered that Pirellula, Pseudanabaena, and Vampirovibrionales preferred to interact with specific Microcystis genotypes in the Summer Major Bloom than with other genotypes in the Autumn Minor Bloom, while the copepod Skistodiaptomus exhibited the opposite pattern. In conclusion, the transition patterns of cyanoHAB-related modules and their key components could be crucial in the succession of Microcystis genotypes and to enhance the understanding of microbial ecology in an aquatic environment.

ACS Style

Seong-Jun Chun; Yingshun Cui; Jay Jung Lee; In-Chan Choi; Hee-Mock Oh; Chi-Yong Ahn. Network analysis reveals succession of Microcystis genotypes accompanying distinctive microbial modules with recurrent patterns. Water Research 2019, 170, 115326 .

AMA Style

Seong-Jun Chun, Yingshun Cui, Jay Jung Lee, In-Chan Choi, Hee-Mock Oh, Chi-Yong Ahn. Network analysis reveals succession of Microcystis genotypes accompanying distinctive microbial modules with recurrent patterns. Water Research. 2019; 170 ():115326.

Chicago/Turabian Style

Seong-Jun Chun; Yingshun Cui; Jay Jung Lee; In-Chan Choi; Hee-Mock Oh; Chi-Yong Ahn. 2019. "Network analysis reveals succession of Microcystis genotypes accompanying distinctive microbial modules with recurrent patterns." Water Research 170, no. : 115326.

Article
Published: 07 September 2019 in Environmental Biology of Fishes
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Slow growth is the major obstacle in the production of astaxanthin in Haematococcus lacustris. Introduction of a “red cell inoculation system (RCIS)” reduced the culture time of H. lacustris by 43% by increasing its growth rate and inducing the earlier synthesis of astaxanthin. Red mature H. lacustris cells rather than green cyst cells were re-inoculated to decrease the growth period from 7 to 4 days by producing more zoospore cells. Starved red cells could take up nutrients quickly, thereby achieving faster growth. To further shorten the astaxanthin induction time, FeSO4, NaCl, and NaHCO3 were added to the cells, and their effects were compared. These chemicals accelerated astaxanthin biosynthesis, decreasing the production period from 7 to 4 days. This study focused on faster astaxanthin production to achieve economic feasibility by RCIS and chemical cues. Fast-track growth and a synthesis induction strategy enabled a more economic and efficient production of astaxanthin in H. lacustris.

ACS Style

Sang-Ah Lee; Nakyeong Lee; Hee-Mock Oh; Dae Geun Kim; Chi-Yong Ahn. Fast-track production of astaxanthin by reduced cultivation time with the “red cell inoculation system” (RCIS) and various chemical cues in Haematococcus lacustris. Environmental Biology of Fishes 2019, 32, 41 -50.

AMA Style

Sang-Ah Lee, Nakyeong Lee, Hee-Mock Oh, Dae Geun Kim, Chi-Yong Ahn. Fast-track production of astaxanthin by reduced cultivation time with the “red cell inoculation system” (RCIS) and various chemical cues in Haematococcus lacustris. Environmental Biology of Fishes. 2019; 32 (1):41-50.

Chicago/Turabian Style

Sang-Ah Lee; Nakyeong Lee; Hee-Mock Oh; Dae Geun Kim; Chi-Yong Ahn. 2019. "Fast-track production of astaxanthin by reduced cultivation time with the “red cell inoculation system” (RCIS) and various chemical cues in Haematococcus lacustris." Environmental Biology of Fishes 32, no. 1: 41-50.

Original research article
Published: 17 July 2019 in Frontiers in Microbiology
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To elucidate the interspecies connectivity between cyanobacteria and other bacteria (non-cyanobacteria) during cyanobacterial harmful algal blooms (cyanoHABs), samples were collected from the Nakdong River, Korea, from June 2016 to August 2017, and microbial recurrent association network (MRAN) analysis was performed to overcome the limitations of conventional network analysis. Microcystis blooms were tightly linked with Pseudanabaena in summer and were accompanied by significant changes in the non-cyanobacterial community composition (nCCC) compared to non-bloom period. Riverine bacterial communities could be clearly separated into modules that were involved in the formation, maintenance, and decomposition of cyanoHABs. Roseomonas and Herbaspirillum were directly linked with major cyanobacteria and assigned to connector and module hub in cyanoHABs-related modules, respectively. The functional profiles of the cyanoHABs-related modules suggested that nitrate reduction, aerobic ammonia oxidation, fermentation, and hydrocarbon degradation could be increased during the Microcystis bloom periods. In conclusion, MRAN analysis revealed that specific bacteria belonging to cyanoHABs-related module, including connectors and module hubs, appeared to contribute to the development and collapse of cyanoHABs. Therefore, to understand cyanoHABs, a modular microbial perspective may be more helpful than a single bacterial species perspective.

ACS Style

Seong-Jun Chun; Yingshun Cui; Chang Soo Lee; A Ra Cho; Kiwoon Baek; Ahyoung Choi; So-Ra Ko; Hyung-Gwan Lee; Seungwoo Hwang; Hee-Mock Oh; Chi-Yong Ahn. Characterization of Distinct CyanoHABs-Related Modules in Microbial Recurrent Association Network. Frontiers in Microbiology 2019, 10, 1637 .

AMA Style

Seong-Jun Chun, Yingshun Cui, Chang Soo Lee, A Ra Cho, Kiwoon Baek, Ahyoung Choi, So-Ra Ko, Hyung-Gwan Lee, Seungwoo Hwang, Hee-Mock Oh, Chi-Yong Ahn. Characterization of Distinct CyanoHABs-Related Modules in Microbial Recurrent Association Network. Frontiers in Microbiology. 2019; 10 ():1637.

Chicago/Turabian Style

Seong-Jun Chun; Yingshun Cui; Chang Soo Lee; A Ra Cho; Kiwoon Baek; Ahyoung Choi; So-Ra Ko; Hyung-Gwan Lee; Seungwoo Hwang; Hee-Mock Oh; Chi-Yong Ahn. 2019. "Characterization of Distinct CyanoHABs-Related Modules in Microbial Recurrent Association Network." Frontiers in Microbiology 10, no. : 1637.

Journal article
Published: 24 June 2019 in Scientific Reports
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To investigate the interactions between bacterial species in relation to the biotic and abiotic environmental fluctuations, free-living (FL), nanoparticle-associated (NP), and microparticle-associated (MP) bacterial community compositions (BCCs) were analyzed. A total of 267 samples were collected from July to December 2016 in the dynamic and shallow southern coastal water of Korea. The variations in BCC mostly depended on planktonic size fraction. Network analysis revealed water depth-dependent co-occurrence patterns of coastal bacterial communities. Higher interspecies connectivity was observed within FL bacteria than NP/MP bacteria, suggesting that FL bacteria with a streamlined genome may need other bacterial metabolites for survival, while the NP/MP copiotrophs may have the self-supporting capacity to produce the vital nutrients. The analysis of topological roles of individual OTUs in the network revealed that several groups of metabolically versatile bacteria (the marine Roseobacters, Flavobacteriales, Desulfobacterales, and SAR406 clade) acted as module hubs in different water depth. In conclusion, interspecies interactions dominated in FL bacteria, compared to NP and MP bacteria; modular structures of bacterial communities and keystone species strongly depended on the water depth-derived environmental factors. Furthermore, the multifunctional, versatile FL bacteria could play pivotal roles in dynamic shallow coastal ecosystems.

ACS Style

Yingshun Cui; Seong-Jun Chun; Seung Ho Baek; Minji Lee; Yunji Kim; Hyung-Gwan Lee; So-Ra Ko; Seungwoo Hwang; Chi-Yong Ahn; Hee-Mock Oh. The water depth-dependent co-occurrence patterns of marine bacteria in shallow and dynamic Southern Coast, Korea. Scientific Reports 2019, 9, 1 -13.

AMA Style

Yingshun Cui, Seong-Jun Chun, Seung Ho Baek, Minji Lee, Yunji Kim, Hyung-Gwan Lee, So-Ra Ko, Seungwoo Hwang, Chi-Yong Ahn, Hee-Mock Oh. The water depth-dependent co-occurrence patterns of marine bacteria in shallow and dynamic Southern Coast, Korea. Scientific Reports. 2019; 9 (1):1-13.

Chicago/Turabian Style

Yingshun Cui; Seong-Jun Chun; Seung Ho Baek; Minji Lee; Yunji Kim; Hyung-Gwan Lee; So-Ra Ko; Seungwoo Hwang; Chi-Yong Ahn; Hee-Mock Oh. 2019. "The water depth-dependent co-occurrence patterns of marine bacteria in shallow and dynamic Southern Coast, Korea." Scientific Reports 9, no. 1: 1-13.

Journal article
Published: 14 June 2019 in Biomass and Bioenergy
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During the mass production of microalgal biodiesel in temperate countries, one of the major obstacles is the lower growth in winter. Therefore, a domestic psychrotolerant microalga, Acutodesmus obliquus MR, was isolated, and its growth and lipid productivity were characterized. The optimal nitrogen concentration for growth was 50 mg-N L−1 at 10 °C, but it increased to over 120 mg-N L−1 at 25 °C. Lipid productivity was also higher under lower nitrogen concentrations at 10 °C but decreased with increasing nitrogen concentrations. Lipid productivity was optimal under lower nutrient concentrations at 10 °C but decreased at higher concentrations. Although the growth rate increased under the mixotrophic mode with higher nitrogen concentrations, lipid productivity was not enhanced due to the decreased lipid content. The quality of fatty acid composition (C16:0, C18:1 and C18:2 > 60%) for biodiesel was improved at low temperature. Since optimum nitrogen concentration shifts depending on temperature in Acutodesmus obliquus MR, nitrogen concentration should be adjusted along the seasonal temperature change to maximize biomass production.

ACS Style

Nakyeong Lee; Hyung-Seok Oh; Hee-Mock Oh; Hee-Sik Kim; Chi-Yong Ahn. Enhanced growth and lipid production in psychrotolerant Acutodesmus by controlling temperature-dependent nitrogen concentration. Biomass and Bioenergy 2019, 127, 105267 .

AMA Style

Nakyeong Lee, Hyung-Seok Oh, Hee-Mock Oh, Hee-Sik Kim, Chi-Yong Ahn. Enhanced growth and lipid production in psychrotolerant Acutodesmus by controlling temperature-dependent nitrogen concentration. Biomass and Bioenergy. 2019; 127 ():105267.

Chicago/Turabian Style

Nakyeong Lee; Hyung-Seok Oh; Hee-Mock Oh; Hee-Sik Kim; Chi-Yong Ahn. 2019. "Enhanced growth and lipid production in psychrotolerant Acutodesmus by controlling temperature-dependent nitrogen concentration." Biomass and Bioenergy 127, no. : 105267.

Journal article
Published: 06 June 2019 in International Journal of Systematic and Evolutionary Microbiology
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A Gram-stain-negative, non-motile, rod-shaped, aerobic bacterial strain, designated HC2T, was isolated from the phycosphere of Haematococcus lacustris NIES 144 culture. Strain HC2T was able to grow at pH 4.5–8.0, at 4–32 °C and in the presence of 0–2 % (w/v) NaCl. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain HC2T was affiliated to the genus Mucilaginibacter and shared the highest sequence similarity with Mucilaginibacter lappiensis ANJKI2T (98.20 %) and Mucilaginibacter sabulilitoris SMS-12T (98.06 %). Strain HC2T contained summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and iso-C15 : 0 as the major fatty acids (>10.0 %). The major polar lipids were phosphatidylethanolamine, one unidentified aminophospholipid, one unidentified phospholipid, two unidentified aminolipids and four unidentified lipids. The respiratory quinone was menaquinone 7 (MK-7). The genomic DNA G+C content was 42.0 %. On the basis of the phenotypic, chemotaxonomic and phylogenetic characteristics, strain HC2T represents a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter inviolabilis sp. nov. is proposed. The type strain is HC2T (=KCTC 82084T=JCM 34116T).

ACS Style

Sang-Ah Lee; Ve Van Le; So-Ra Ko; Nakyeong Lee; Hee-Mock Oh; Chi-Yong Ahn. Mucilaginibacter inviolabilis sp. nov., isolated from the phycosphere of Haematococcus lacustris NIES 144 culture. International Journal of Systematic and Evolutionary Microbiology 2019, 71, 004668 .

AMA Style

Sang-Ah Lee, Ve Van Le, So-Ra Ko, Nakyeong Lee, Hee-Mock Oh, Chi-Yong Ahn. Mucilaginibacter inviolabilis sp. nov., isolated from the phycosphere of Haematococcus lacustris NIES 144 culture. International Journal of Systematic and Evolutionary Microbiology. 2019; 71 (3):004668.

Chicago/Turabian Style

Sang-Ah Lee; Ve Van Le; So-Ra Ko; Nakyeong Lee; Hee-Mock Oh; Chi-Yong Ahn. 2019. "Mucilaginibacter inviolabilis sp. nov., isolated from the phycosphere of Haematococcus lacustris NIES 144 culture." International Journal of Systematic and Evolutionary Microbiology 71, no. 3: 004668.

Original paper
Published: 18 March 2019 in International Journal of Environmental Science and Technology
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Diverse methods have been applied to control cyanobacterial bloom, but no universal method has been developed. Periphytons (attached microalgae) compete with cyanobacteria for nutrients and thus were cultivated and regularly harvested for nutrient reduction and bloom control. Four mesocosms, with different amounts of supporting materials, were constructed in Daechung Reservoir, Korea. Cyanobacterial growth decreased to one-third by the growth of attached microalgae, as compared to the control mesocosm. The highest periphyton biomass productivity of 111 mg m−1 d−1 was found, corresponding to the removal of 87.4 μg P L−1 in 24 days. Dissolved microcystin concentration was maintained less than 1 μg L−1. Periphytic microalgae grew well even under lower temperatures. Total biomass productivity was lower (25.9 mg m−1 d−1) than in the warmer season but sufficient to reduce the cyanobacterial growth. The developed periphyton cultivation system showed a good potential in terms of nutrient reduction and cyanobacterial bloom control.

ACS Style

S.-R. Ko; Ankita Srivastava; N. Lee; L. Jin; H.-M. Oh; C.-Y. Ahn. Bioremediation of eutrophic water and control of cyanobacterial bloom by attached periphyton. International Journal of Environmental Science and Technology 2019, 16, 4173 -4180.

AMA Style

S.-R. Ko, Ankita Srivastava, N. Lee, L. Jin, H.-M. Oh, C.-Y. Ahn. Bioremediation of eutrophic water and control of cyanobacterial bloom by attached periphyton. International Journal of Environmental Science and Technology. 2019; 16 (8):4173-4180.

Chicago/Turabian Style

S.-R. Ko; Ankita Srivastava; N. Lee; L. Jin; H.-M. Oh; C.-Y. Ahn. 2019. "Bioremediation of eutrophic water and control of cyanobacterial bloom by attached periphyton." International Journal of Environmental Science and Technology 16, no. 8: 4173-4180.

Journal article
Published: 13 February 2019 in Bioresource Technology
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This study examined the effects of a bacterial community and extracellular polymeric substances (EPS) on Ettlia sp. flocculation. The growth rate, flocculation efficiency (FE), bacterial community, and EPS profile of axenic and xenic Ettlia cultures were monitored during 46 days of cultivation. For the xenic culture, with a great abundance of growth-promoting and flocculation-inducing bacteria, the biomass density was 18.75% higher and its FE reached 100% in the mid-stationary phase. Moreover, microscopic observation and a quantitative analysis of the EPS revealed the exclusive presence of long filamentous EPS and more compact structure in the xenic Ettlia culture, possibly explaining its better FE. Notwithstanding, for the axenic culture, despite a lower biomass density and reduced abundance of EPS, its FE reached 92.54% in the mid-stationary phase. Thus, the role of the bacterial community was found to be supportive rather than vital for the high settleability of the self-flocculating Ettlia microalgal culture.

ACS Style

Chau Hai Thai Vu; Seong-Jun Chun; Seong-Hyun Seo; Yingshun Cui; Chi-Yong Ahn; Hee-Mock Oh. Bacterial community enhances flocculation efficiency of Ettlia sp. by altering extracellular polymeric substances profile. Bioresource Technology 2019, 281, 56 -65.

AMA Style

Chau Hai Thai Vu, Seong-Jun Chun, Seong-Hyun Seo, Yingshun Cui, Chi-Yong Ahn, Hee-Mock Oh. Bacterial community enhances flocculation efficiency of Ettlia sp. by altering extracellular polymeric substances profile. Bioresource Technology. 2019; 281 ():56-65.

Chicago/Turabian Style

Chau Hai Thai Vu; Seong-Jun Chun; Seong-Hyun Seo; Yingshun Cui; Chi-Yong Ahn; Hee-Mock Oh. 2019. "Bacterial community enhances flocculation efficiency of Ettlia sp. by altering extracellular polymeric substances profile." Bioresource Technology 281, no. : 56-65.