Z-Hun Kim
Inha University
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Publication
Featured researches published by Z-Hun Kim.
Journal of Microbiology and Biotechnology | 2016
Z-Hun Kim; Hanwool Park; Choul-Gyun Lee
A green microalga, Tetraselmis sp., was cultivated in the coastal seawater of Young-Heung Island using semi-permeable membrane photobioreactors (SPM-PBRs) in different seasons. The microalgae in the SPM-PBRs were able to grow on nutrients diffused into the PBRs from the surrounding seawater through SPMs. The biomass productivity varied depending on the ion permeabilities of the SPMs and environmental conditions, whereas the quality and quantity of fatty acids were constant. The temperature of seawater had a greater influence than solar radiation did on productivity of Tetraselmis sp. in SPM-PBRs. SPM-PBRs could provide technologies for concurrent algal biomass and fatty acids production, and eutrophication reduction in the ocean.
Biotechnology and Bioprocess Engineering | 2017
Z-Hun Kim; Yong-Sung Park; Young-Jin Ryu; Choul-Gyun Lee
Some artificial light sources able to emit photons at specific wavelengths, such as LEDs, are useful for studying the effects of light quality on microalgal growth and production of fatty acids; however, they should not be used for outdoor cultivation of microalgae to produce bioenergy. Instead, various light filters capable of selectively transmitting red, blue, and red+blue light regions in solar radiation were used to cover 0.4 L bubble column photobioreactors to cultivate Tetraselmis sp. KCTC12236BP and investigate the influence of light quality on microalgal growth and fatty acid production. Biomass and fatty acid productivities in red light (0.10 ± 0.05 g/L/day and 11.8 ± 0.5 mg/L/day, respectively) were 7 ~ 53% and 9 ~ 61% higher than other colored lights based on the same number of supplied photons, respectively. The composition of fatty acids did not change significantly in response to transmitted light qualities of the filter. The ratio of saturated to unsaturated fatty acids was 3:7, and their contents were 12% in all groups, which corresponds with the results of LEDs. Plotting biomass and fatty acid productivity over the red photon fraction in supplied light revealed that increased productivities were closely correlated with red photon fraction in the filtered light. Overall, the results presented herein indicate that enhanced production of algal fatty acid could be achieved by application of light filters in outdoor settings without artificial lights.
Journal of Microbiology and Biotechnology | 2018
Mi-Ae Han; Seong-Joo Hong; Z-Hun Kim; Byung-Kwan Cho; Hookeun Lee; Hyung-Kyoon Choi; Choul-Gyun Lee
Lipids in microalgae are energy-rich compounds and considered as an attractive feedstock for biodiesel production. To redirect carbon flux from competing pathways to the fatty acid synthesis pathway of Tetraselmis sp., we used three types of chemical inhibitors that can block the starch synthesis pathway or photorespiration, under nitrogen-sufficient and nitrogen-deficient conditions. The starch synthesis pathway in chloroplasts and the cytosol can be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 1,2-cyclohexane diamine tetraacetic acid (CDTA), respectively. Degradation of glycine into ammonia during photorespiration was blocked by aminooxyacetate (AOA) to maintain biomass concentration. Inhibition of starch synthesis pathways in the cytosol by CDTA increased fatty acid productivity by 27% under nitrogen deficiency, whereas the blocking of photorespiration in mitochondria by AOA was increased by 35% under nitrogen-sufficient conditions. The results of this study indicate that blocking starch or photorespiration pathways may redirect the carbon flux to fatty acid synthesis.
Journal of Microbiology and Biotechnology | 2016
Z-Hun Kim; Hanwool Park; Ho-Sang Lee; Choul-Gyun Lee
A split-column photobioreactor (SC-PBR), consisting of two bubble columns with different sizes, was developed to enhance the photon utilization efficiency in an astaxanthin production process from Haematococcus lacustris. Among the two columns, only the smaller column of SC-PBR was illuminated. Astaxanthin productivities and photon efficiencies of the SC-PBRs were compared with a standard bubble-column PBR (BC-PBR). Astaxanthin productivity of SC-PBR was improved by 28%, and the photon utilization efficiencies were 28-366% higher than the original BC-PBR. The results clearly show that the effective light regime of SC-PBR could enhance the production of astaxanthin.
Journal of Microbiology and Biotechnology | 2018
Young-Jin Ryu; Z-Hun Kim; Seul Gi Lee; Ji-Hyun Yang; Hee-Yong Shin; Choul-Gyun Lee
Novel carbon-based solid acid catalysts were synthesized through a sustainable route from lipid-extracted microalgal residue of Dunaliella tertiolecta, for biodiesel production. Two carbon-based solid acid catalysts were prepared by surface modification of bio-char with sulfuric acid (H₂SO₄) and sulfuryl chloride (SO₂Cl₂), respectively. The treated catalysts were characterized and their catalytic activities were evaluated by esterification of oleic acid. The esterification catalytic activity of the SO₂Cl₂-treated bio-char was higher (11.5 mmol Prod.∙h⁻¹∙g Cat. ⁻¹) than that of commercial catalyst silica-supported Nafion SAC-13 (2.3 mmol Prod.∙h⁻¹∙g Cat. ⁻¹) and H₂SO₄-treated bio-char (5.7 mmol Prod.∙h⁻¹∙g Cat. ⁻¹). Reusability of the catalysts was examined. The catalytic activity of the SO₂Cl₂-modified catalyst was sustained from the second run after the initial activity dropped after the first run and kept the same activity until the fifth run. It was higher than that of first-used Nafion. These experimental results demonstrate that catalysts from lipid-extracted algae have great potential for the economic and environment-friendly production of biodiesel.
Biotechnology and Bioprocess Engineering | 2016
Z-Hun Kim; Nguyen Ngoc Thanh; Ji-Hyun Yang; Hanwool Park; Moon-Young Yoon; Jung-Keug Park; Choul-Gyun Lee
Chemically-processed clays (PRCs) by base and acid treatments were developed to effectively remove microalgae, and their removal efficiencies were evaluated and compared to that of natural clay. The processed clays were produced by using sodium hydroxide and different amounts of sulfuric acid, and their characteristics were analyzed. Microalgae removal efficiency of the clay was varied depending on the amount of sulfuric acid used in treatments. When adding 1 g/L of a PRC-D type (treated with 1.5 v/w sulfuric acid) to the Microcystis aeruginosa suspension (1 × 106 cells/mL), the highest removal performance (87.3 ± 1.5%) without significant pH variation of the suspension was found among tested PRCs, whereas that of natural clay was 32.1 ± 2.2%. Finally, when selected PRC-D showing best efficiency was applied to lake water taken at a local algae bloomed lake, it exhibited 77.6% removal efficiency of microalgae, indicating 1.7 times higher than the natural clay. The results suggest that processed clays in this study could contribute to effective removal of microalgae in the algal-bloomed area with minimal environmental impact.
Enzyme and Microbial Technology | 2006
Z-Hun Kim; Sun-Hyung Kim; Ho-Sang Lee; Choul-Gyun Lee
Biotechnology and Bioprocess Engineering | 2010
Hai-Linh Tran; Ji-Sue Kwon; Z-Hun Kim; Youkwan Oh; Choul-Gyun Lee
Archive | 2008
Choul-Gyun Lee; Z-Hun Kim
Enzyme and Microbial Technology | 2006
Ho-Sang Lee; Mun-Won Seo; Z-Hun Kim; Choul-Gyun Lee