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Cho, Kichul,Cho, Dae-Hyun,Heo, Jina,Kim, Urim,Lee, Yong Jae,Choi, Dong-Yun,Kim, Hee-Sik Elsevier 2019 Bioresource technology Vol.281 No.-
<P><B>Abstract</B></P> <P>Algal growth limitation in large-scale cultivation mostly results from high level synthesis of photosynthetic pigments, owing to self-shading effects and attenuation of light distribution. To overcome this problem, here we investigated the influence of nitrogen modulation on changes in antenna pigments as well as biomass and lipid production by <I>Chlorella vulgaris</I> under a chemostat continuous cultivation mode. The production of algal antenna pigments, including chlorophylls and carotenoids, was promoted in a total nitrogen (TN) concentration-dependent manner. Maximum algal biomass and lipid production were obtained from 70 mg/L of TN concentration along with a significant increase in light transmittance and reduction in antenna pigments. Furthermore, the composition of polyunsaturated fatty acids remarkably augmented at low TN concentrations. These results suggest that the reduction in algal antenna pigment synthesis via modulation of nitrogen concentration may serve as an effective strategy to enhance algal biomass and lipid production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TN-modulated algal cultivation was performed under chemostat mode. </LI> <LI> Antenna pigment reduction was observed at low TN concentration. </LI> <LI> Algal biomass and lipid production increased from OLTZ. </LI> <LI> PUFA production significantly increased at low TN concentration. </LI> </UL> </P>
Cho, Kichul,Heo, Jina,Cho, Dae-Hyun,Tran, Quynh-Giao,Yun, Jin-Ho,Lee, Sang-Moo,Lee, Yong Jae,Kim, Hee-Sik Elsevier 2019 Algal research Vol.37 No.-
<P><B>Abstract</B></P> <P>The concept of sustainable biodiesel production using microalgae has attracted a lot of attention as an emerging green energy technology. However, low algal biomass and lipid productivity hinder cost-effective biodiesel production. To overcome these problems, this study examined the effect of bacterial volatile compounds (VCs) on the growth and lipid production of microalga <I>Chlorella vulgaris</I> OW-01. The VCs of phycospheric bacteria including <I>Hyphomonas</I> sp., <I>Rhizobium</I> sp., and <I>Sphingomonas</I> sp. efficiently augmented algal biomass in a newly developed VCs experimental apparatus. Moreover, an apparent increase in total lipid content along with a 2.34-fold increase in productivity was observed in <I>Hyphomonas</I> sp. VCs–exposed algal biomass. Fatty acid methyl esters (FAME) composition also demonstrated that the algal biodiesel properties were somewhat modified by exposure to bacterial VCs. A LiOH filter-inducing CO<SUB>2</SUB>-removed bacterial VCs (CRBVCs) also enhanced daily growth of microalgae, as compared to the control culture (aeration), indicating that CRBVC included growth-promoting volatiles. Of those factors, volatile indole was identified as a possible algal growth enhancing factor, and it showed a higher growth-promoting effect than dimethyl disulfide and dimethyl trisulfide. Based on these results, it is speculated that the use of bacterial VCs for algal cultivation is a promising future bioprocess for the algal biomass and biodiesel production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Enhanced algal biomass and lipid productivity were obtained by bacterial vo </LI> <LI> CO<SUB>2</SUB>-removed bacterial volatile compounds (VCs) promoted algal biomass production. </LI> <LI> Volatile indole was detected as a growth-enhancing factor among the bacterial VCs. </LI> </UL> </P>
Cho, Kichul,Wencheng, Li,Takeshita, Satoshi,Seo, Jung-Kil,Chung, Young-Ho,Kim, Daekyung,Oda, Tatsuya Elsevier 2017 Aquatic toxicology Vol.189 No.-
<P><B>Abstract</B></P> <P> <I>Heterocapsa circularisquama</I>, a harmful dinoflagellate, has multiple haemolytic toxins that are considered to be involved in the toxic mechanism against shellfish and certain species of zooplankton. To evaluate the further nature of the toxins of <I>H. circularisquama</I>, we investigated its effects on several species of bacteria. By colony formation assay, we found that <I>H. circularisquama</I> had antibacterial activity toward the marine bacterium <I>Vibrio alginolyticus</I> in a cell density-dependent manner. When the inoculated bacterial cells were co-cultured with <I>H. circularisquama</I> under dinoflagellate cell culture conditions, the bacterial growth was significantly suppressed, whereas the number of live bacterial cells increased when cultured in the medium alone. Since the cell-free culture supernatant and the ruptured dinoflagellate cell suspension showed no toxic effects on <I>V. alginolyticus</I>, it is speculated that direct cell-to-cell contact mediated by the live dinoflagellate cells may be the major toxic mechanism. The decrease in bactericidal activity of theca-removed dinoflagellate cells may further support this speculation. <I>H. circularisquama</I> also showed bactericidal activities towards <I>Escherichia coli</I> and <I>Staphylococcus aureus</I>. In the dinoflagellate/bacteria co-culture system, the number of live bacterial cells declined with increasing incubation time. Light-dependent antibacterial activity of the ruptured dinoflagellate cells against <I>S. aureus</I> was observed, whereas no such activity was detected against <I>E. coli</I>. These results suggest that intracellular photosensitising bactericidal toxins, which were previously found to be porphyrin derivatives, may have specificity towards gram-positive bacteria. Based on these results together with previous studies, it is obvious that <I>H. circularisquama</I> possesses antibacterial activity, which may be mediated through toxins located on its cell surface. It is likely that such toxins play a role in the defence mechanism against predators and infectious bacteria. Although the exact biological significance of intracellular photosensitising toxins is still unclear, such toxins may have potential to be developed as novel photo-controllable antibiotics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>H. circularisquama</I> (HC) exhibits anti-bacterial activity toward <I>V. alginolyticus</I>. </LI> <LI> Direct cell contact mediated by the live HC cells may be the major toxic mechanism. </LI> <LI> HC also shows bactericidal activities towards <I>E. coli</I> and <I>S. aureus</I>. </LI> <LI> HC has intracellular photosensitizing agents toxic to <I>S. aureus</I>. </LI> </UL> </P>
Cho, Kichul,Lee, Sang-Moo,Cho, Dae-Hyun,Heo, Jina,Lee, Yong Jae,Kim, Hee-Sik Elsevier 2019 Biomass & bioenergy Vol.127 No.-
<P><B>Abstract</B></P> <P>Outdoor algal cultivation is frequently limited by bacterial contaminants. The aim of this study was to develop a biological control technique for removing bacterial contaminants using a small-size ciliate. During the cultivation of <I>Chlorell</I>a sp. HS2 in a designed raceway pond, the bacterial population was significantly reduced by the ciliate strain. 18S rDNA analysis identified the ciliate as <I>Colpoda</I> sp. HSP-001. To verify selective bacterial grazing by the ciliate, an isolated phycospheric bacterium <I>Microbacterium</I> sp. was co-cultivated with <I>Chlorella</I> sp. HS2 while varying the ciliate cell concentrations. <I>Colpoda</I> sp. efficiently eliminated bacterial cells, whereas no algal grazing was observed by fluorescence microscopy. Based on the results, the utilization of <I>Colpoda</I> sp. HSP-001 in an outdoor algal cultivation system is a cost-effective strategy for controlling bacterial contamination without degrading the algal biomass.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Selective suppression of bacteria by a ciliate strain was observed in algal culture. </LI> <LI> Enhanced algal growth was achieved by control of bacterial abundance by ciliate. </LI> <LI> The isolated ciliate strain was identified as <I>Colpoda</I> sp. HSP-001. </LI> </UL> </P>
Haemolytic activity and reactive oxygen species production of four harmful algal bloom species
Cho, Kichul,Kasaoka, Takuya,Ueno, Mikinori,Basti, Leila,Yamasaki, Yasuhiro,Kim, Daekyung,Oda, Tatsuya Taylor Francis 2017 European journal of phycology Vol.52 No.3
<P>Based on haemolytic activity and reactive oxygen species (ROS) production of Chattonella marina, Chattonella antiqua, Heterocapsa circularisquama, Alexandrium tamiyavanichii and Karenia mikimotoi, the species were categorized into four types. (1) H. circularisquama: haemolytic activity was detected in both cell suspension and cell-free culture supernatant, but with greater activity in cell suspension than in the supernatant suggesting the presence of both cell surface and secreted haemolytic agents. (2) A. tamiyavanichii: equal haemolytic activities were detected in both the cell suspension and cell-free culture supernatant suggesting the presence of only secreted haemolytic agents. (3) K. mikimotoi: haemolytic activity was detected only in the cell suspension, indicating haemolytic agents occur only on the cell surface. (4) C. marina and C. antiqua: no significant haemolytic activity was detected in either cell suspension or cell-free culture supernatant, but high ROS were detected in the cell suspensions. Heterocapsa circularisquama and K. mikimotoi showed lethal effects on rotifers (Brachionus plicatilis), whereas A. tamiyavanichii, C. marina and C. antiqua had no effect. Our results suggest that H. circularisquama, K. mikimotoi and A. tamiyavanichii produce haemolytic agents with distinct characteristics, whereas C. marina and C. antiqua have an extremely potent ability to produce ROS.</P>
Using reverse docking to identify potential targets for ginsenosides
Kichul Park,Art E. Cho 고려인삼학회 2017 Journal of Ginseng Research Vol.41 No.4
Background: Ginsenosides are the main ingredients of ginseng, which, in traditional Eastern medicine, has been claimed to have therapeutic values for many diseases. In order to verify the effects of ginseng that have been empirically observed, we utilized the reverse docking method to screen for target proteins that are linked to specific diseases. Methods: We constructed a target protein database including 1,078 proteins associated with various kinds of diseases, based on the Potential Drug Target Database, with an added list of kinase proteins. We screened 26 kinds of ginsenosides of this target protein database using docking. Results: We found four potential target proteins for ginsenosides, based on docking scores. Implications of these “hit” targets are discussed. From this screening, we also found four targets linked to possible side effects and toxicities, based on docking scores. Conclusion: Our method and results can be helpful for finding new targets and developing new drugs from natural products.