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Jung, Woongsic,Kim, Eun Jae,Han, Se Jong,Kang, Sung-Ho,Choi, Han-Gu,Kim, Sanghee Informa UK (TaylorFrancis) 2017 Preparative biochemistry & biotechnology Vol.47 No.2
<P>Arctic Chlamydomonas sp. is a dominant microalgal strain in cold or frozen freshwater in the Arctic region. The full-length open reading frame of the omega-6 fatty acid desaturase gene (AChFAD6) was obtained from the transcriptomic database of Arctic Chlamydomonas sp. from the KOPRI culture collection of polar micro-organisms. Amino acid sequence analysis indicated the presence of three conserved histidine-rich segments as unique characteristics of omega-6 fatty acid desaturases, and three transmembrane regions transported to plastidic membranes by chloroplast transit peptides in the N-terminal region. The AChFAD6 desaturase activity was examined by expressing wild-type and V254A mutant (Mut-AChFAD6) heterologous recombinant proteins. Quantitative gas chromatography indicated that the concentration of linoleic acids in AChFAD6-transformed cells increased more than 3-fold [6.73 +/- 0.13 mg g(-1) dry cell weight (DCW)] compared with cells transformed with vector alone. In contrast, transformation with Mut-AChFAD6 increased the concentration of oleic acid to 9.23 +/- 0.18 mg g(-1) DCW, indicating a change in enzymatic activity to mimic that of stearoyl-CoA desaturase. These results demonstrate that AChFAD6 of Arctic Chlamydomonas sp. increases membrane fluidity by enhancing denaturation of C18 fatty acids and facilitates production of large quantities of linoleic fatty acids in prokaryotic expression systems.</P>
Cellular growth and fatty acid content of Arctic chlamydomonadalean
Jung, Woongsic,Kim, Eun Jae,Lim, Suyoun,Sim, Hyunji,Han, Se Jong,Kim, Sanghee,Kang, Sung-Ho,Choi, Han-Gu The Korean Society of Phycology 2016 ALGAE Vol.31 No.1
Arctic microalgae thrive and support primary production in extremely cold environment. Three Arctic green microalgal strains collected from freshwater near Dasan Station in Ny-Alesund, Svalbard, Arctic, were analyzed to evaluate the optimal growth conditions and contents of fatty acids. The optimal growth temperature for KNF0022, KNF0024, and KNF0032 was between 4 and 8℃. Among the three microalgal strains, KNF0032 showed the maximal cell number of 1.6 × 107 cells mL<sup>-1</sup> at 4℃. The contents of fatty acids in microalgae biomass of KNF0022, KNF0024, and KNF0032 cultured for 75 days were 37.34, 73.25, and 144.35 mg g<sup>-1</sup> dry cell weight, respectively. The common fatty acid methyl esters (FAMEs) analyzed from Arctic green microalgae consisted of palmitic acid methyl ester (C16:0), 5,8,11-heptadecatrienoic acid methyl ester (C17:3), oleic acid methyl ester (C18:1), linoleic acid methyl ester (C18:2), and α-linolenic acid methyl ester (C18:3). KNF0022 had high levels of heptadecanoic acid methyl ester (26.58%) and heptadecatrienoic acid methyl ester (22.17% of the total FAMEs). In KNF0024 and KNF0032, more than 72.09% of the total FAMEs consisted of mono- and polyunsaturated fatty acids. Oleic acid methyl ester from KNF0032 was detected at a high level of 20.13% of the FAMEs. Arctic freshwater microalgae are able to increase the levels of polyunsaturated fatty acids under a wide range of growth temperatures and can also be used to produce valuable industrial materials.
Gwak, Yunho,Jung, Woongsic,Lee, Yew,Kim, Ji Sook,Kim, Chul Geun,Ju, Ji-Hyun,Song, Chihong,Hyun, Jae-Kyung,Jin, EonSeon The Federation of American Societies for Experimen 2014 The FASEB Journal Vol.28 No.11
<P>The structure and function of the Antarctic marine diatom <I>Chaetoceros neogracile</I> antifreeze protein (Cn-AFP), as well as its expression levels and characteristics of the ice-binding site, were analyzed in the present study. <I>In silico</I> analysis revealed that the <I>Cn-AFP</I> promoter contains both light- and temperature-responsive elements. Northern and Western blot analyses demonstrated that both Cn-AFP transcript and protein expression were strongly and rapidly stimulated by freezing, as well as temperature and high light stress. Immunogold labeling revealed that Cn-AFP is preferentially localized to the intracellular space near the chloroplast membrane. Recombinant Cn-AFP had clear antifreeze activity. Protein-folding simulation was used to predict the putative ice-binding sites in Cn-AFP, and site-directed mutagenesis of the Cn-AFP b-face confirmed their identification.—Gwak, Y., Jung, W., Lee, Y., Kim, J. S., Kim, C. G., Ju, J.-H., Song, C., Hyun, J.-K., Jin, E. An intracellular antifreeze protein from an Antarctic microalga that responds to various environmental stresses.</P>
Lipid Production by Arctic Microalga <i>Chlamydomonas</i> sp. KNF0008 at Low Temperatures
Kim, Eun Jae,Jung, Woongsic,Lim, Suyoun,Kim, Sanghee,Choi, Han-Gu,Han, Se Jong Humana Press 2019 Applied biochemistry and biotechnology Vol.188 No.2
<P> A lipid-producing microalga, <I>Chlamydomonas</I> sp. KNF0008, collected from the Arctic was capable of growing at temperatures ranging from 4 to 20 ℃, and the highest cell density was measured at 15 ℃ and 100 μmol photons m<SUP>-2</SUP> s<SUP>-1</SUP> light intensity under continuous shaking and external aeration. KNF0008 showed the elevated accumulation of lipid bodies under nitrogen-deficient conditions, rather than under nitrogen-sufficient conditions. Fatty acid production of KNF0008 was 4.2-fold (104 mg L<SUP>-1</SUP>) higher than that of <I>C. reinhardtii</I> CC-125 at 15 ℃ in Bold's Basal Medium. The dominant fatty acids were C16:0, C16:4, C18:1, and C18:3, and unsaturated fatty acids (65.69%) were higher than saturated fatty acids (13.65%) at 15 ℃. These results suggested that Arctic <I>Chlamydomonas</I> sp. KNF0008 could possibly be utilized for production of biodiesel during periods of cold weather because of its psychrophilic characteristics. </P>