Dong-Yeon Kim

Cell-wall disruption and lipid/astaxanthin extraction from microalgae: Chlorella and Haematococcus

Recently, biofuels and nutraceuticals produced from microalgae have emerged as major interests, resulting in intensive research of the microalgal biorefinery process. In this paper, recent developments in cell-wall disruption and extraction methods are reviewed, focusing on lipid and astaxanthin production from the biotechnologically important microalgae Chlorella and Haematococcus, respectively. As a common, critical bottleneck for recovery of intracellular components such as lipid and astaxanthin from these microalgae, the composition and structure of rigid, thick cell-walls were analyzed. Various chemical, physical, physico-chemical, and biological methods applied for cell-wall breakage and lipid/astaxanthin extraction from Chlorella and Haematococcus are discussed in detail and compared based on efficiency, energy consumption, type and dosage of solvent, biomass concentration and status (wet/dried), toxicity, scalability, and synergistic combinations. This report could serve as a useful guide to the implementation of practical downstream processes for recovery of valuable products from microalgae including Chlorella and Haematococcus.

α, γ, and normal, abnormal glow discharge modes in radio-frequency capacitively coupled discharges at atmospheric pressure

Discharge modes, α and γ, of a radio-frequency helium capacitively coupled discharge at atmospheric pressure were investigated with the discharge gap distance between electrodes varied from 1 to 5mm. As similarly observed in other experiments, the α and γ mode and the α–γ mode transition were observed with large drops in the voltage (310–179V) and the phase angle between the voltage and current (54°–18°), and a contraction of the plasma volume (8.5–0.17cm3, at 3mm gap distance). The discharge voltage where the α–γ mode transition occurred versus the gap distance showed a similar behavior with the Paschen curve for a gas breakdown. Depending on the gap distance, normal and abnormal glow regimes were observed in the αmode. At 1 and 2mm, the α mode remained in the abnormal glow discharge until the α–γ mode transition occurred as the discharge current increases. At 3mm, however, the α mode was excited as a normal glow discharge with a constant current density (17mA∕cm2) but it became an abnormal glow discharg...

An integrated process for microalgae harvesting and cell disruption by the use of ferric ions

In this study, a simultaneous process of harvesting biomass and extracting crude bio-oil was attempted from wet microalgae biomass using FeCl3 and Fe2(SO4)3 as both coagulant and cell-disrupting agent. A culture solution of Chlorella sp. KR-1 was firstly concentrated to 20 g/L and then proceeded for cell disruption with the addition of H2O2. Optimal dosage were 560 and 1060 mg/L for FeCl3 and Fe2(SO4)3, showing harvesting efficiencies of more than 99%. Optimal extraction conditions were identified via the response surface method (RSM), and the extraction yield was almost the same at 120 °C for both iron salts but FAME compositions after transesterification was found to be quite different. Given iron salts were a reference coagulant in water treatment in general and microalgae harvesting in particular, the present approach of using it for harvesting and oil-extraction in a simultaneous manner can serve as a practical route for the microalgae-derived biodiesel production.

A Feasibility Study for the Cancer Therapy Using Cold Plasma

Cold plasma generated at the atmospheric pressure has been applied to disinfect microorganisms such as bacteria and yeast cells in biomedical research. Especially, due to its low temperature condition, the heat-sensitive medical device can be easily sterilized by the cold plasma treatment. In recent years, the effects of plasma on mammalian cells have arisen as a new issue. Generally, plasma is known to induce intensity dependent necrotic cell death. In this research, we investigate the feasibility of cold plasma treatment for cancer therapy by conducting comparative study of plasma effects on normal and cancer cells. We select THLE-2 (human liver normal cell) and SK-Hep1 (human liver metathetic cancer cell) as our target cells. Two types of cells have different onset plasma conditions for the necrosis, which may be explained by difference in electrical properties of these two cell types. Based on this work, a feasibility of the novel selective cancer therapy is tested.

Spectroscopic characterization of rovibrational temperatures in atmospheric pressure He∕CH4 plasmas

Atmospheric pressure of helium (He) and methane (CH4) mixture discharge characteristics are investigated using emission spectroscopic methods. Plasmas are produced in a radio frequency capacitively coupled device at atmospheric pressure in the ambient air. Without the CH4 gas introduced in the plasma, the emission spectrum exhibits typical helium discharge characteristics showing helium atomic lines with nitrogen molecular bands and oxygen atomic lines resulting from air impurities. Addition of a small amount (<1%) of CH4 to the supplied He results in the emission of CN (B2∑+-X2∑+: violet system) and CH (A2Δ-X2∏: 430nm system) molecular bands. Analyzing the CN and CH diatomic molecular emission spectra, the vibrational temperature (Tvib) and rotational temperature (Trot) are simultaneously obtained. As input power levels are raised from 20Wto200W, Tvib and Trot are increased from 4230Kto6310K and from 340Ku2009to500K, respectively. On the contrary, increasing the CH4 amount brings about the decrease of both t...

Acidified-flocculation process for harvesting of microalgae: Coagulant reutilization and metal-free-microalgae recovery

Chemical flocculation is considered to be an overall low-cost and up-scalable process for harvesting of microalgae. In this study a new flocculation approach utilizing metal coagulant (Fe2(SO4)3) and sulfuric acid (H2SO4) was introduced for harvesting of Chlorella sp. KR-1, which overcome two main issues of contamination and reuse of coagulant. Reduction of pH successfully released precipitates attached to the microalgae, and the remaining acidic solution containing recovered ferric ions could be reused for harvesting up to three times with high, better-than 98% efficiencies. Moreover, the acid-treated microalgal biomass could be directly used for lipid extraction without additional catalyst. High extraction yields of around 32% were achieved with FAME conversion efficiencies of around 90%. The integrated approach devised in the present study is expected to make the best use of the age-old yet effective harvesting means of flocculation, which can be a practical and economical option in microalgal biorefinery.

An innovative dual fuel cell to capture and collect pure NO X from flue gases

Nitrogen monoxide (NO), a major air pollutant, can be directly used as a precursor for nitrogen fertilizer production as long as it is collected in a pure form. In this study, an innovative dual fuel cell system was designed for the efficient capture and collection of pure NOX from industrial flue gases as well as for electricity generation. The system consisted of a methanol/ferric-EDTA fuel cell for NOX capture and a ferrous-EDTA–NO/air fuel cell for captured NOX collection. In a separation operation, the maximum power densities, which were obtained at pH 2 and 20xa0°C, were 785 and 1,840xa0mWxa0m−2 in FC1 and FC2, respectively, and increased with temperature. The highest overall outputs from FC1 and FC2 were measured at pH 2, a result that is possibly attributable to the redox potential difference between the anolyte and catholyte in the fuel cells. In the combined operation, ferrous-EDTA–NO prepared in the cathode compartment of FC1 was successfully and efficiently converted to ferric-EDTA and NO in the anode compartment of FC2. The present approach was considered advantageous for advanced NOX reuse technology in the respect that valuable products, such as fertilizer, could be produced.

Application of Fe(NO3)3-based as nitrogen source and coagulant for cultivation and harvesting of Chlorella sorokiniana

In this study, Chlorella sorokiniana was successfully cultivated in the recycled medium whose nitrogen was supplied directly from the coagulant, Fe(NO3)3. With a dosage of 0.80g/L, harvesting efficiency of 95% could be achieved. What is more, this amount of nitrate in the coagulant was enough to fully support the growth of C. sorokiniana during the 8day cultivation period, almost as much as the initial nitrogen content in the BG11 culture medium. Other nutrients had to be supplemented, however, with at least 50% amount as in the BG11 recipe. C. sorokiniana culture grown in recycled medium replenished with 50% of nutrients showed much higher Fatty acid methyl esters (FAME) productivity than the control, with 88.3mg/L/day. The recycle of the medium is certainly a way of reducing the water footprint for the purpose of microalgae-derived biodiesel production; better still, it may serve to lower the nutrient footprint.

Is Advertising on an AI Speaker Effective?: The Role of Interactivity, Product type, and Thematic Congruence

Unlike the existing media, media based on voice interface has emerged. Amazons Echo and Googles Google Home are a typical product that allows users to interact with their devices through a voice interface. With the advent of these devices, many changes have occurred, but changes in a marketing method are particularly noticeable. Whereas existing advertisements were unidirectional and product-oriented ads that were sourced on the Internet or mobile, advertisements on an AI speaker would be in a bi-directional, context-based advertisement format. This study examines the types of advertisements that can be applied effectively in an AI speaker environment and discuss practical application methods. 160 participants were divided into eight groups to investigate the effects of interactivity, product types, thematic congruence, and sponsored messages. Interactivity in advertising is expected to become even more important with the high penetration of AI speakers.

Spectroscopic characterization of a- and .-mode in a capacitively-coupled plasma in the high pressure range up to atmospheric pressure

Summary form only given. Optical characteristics of different capacitive discharge modes, namely alpha- and gamma-mode, were investigated in the high gas pressure (10 torr) up to the atmospheric pressure. The plasma was produced between parallel copper electrodes using a 13.56 MHz RF source. An alpha-mode was excited as igniting the plasma at a low current region. At a certain discharge voltage and current, however, the alpha-mode was abruptly transformed into a gamma-mode with a voltage drop and a discharge volume contraction. Using optical spectroscopic methods, different discharge parameters were investigated. Because of the helium discharge gas, both discharge modes emitted intense excited atomic helium spectral lines, such as 587.6 nm and 667.8 nm. From the experimental results, the gamma-mode showed more intense emission and higher excitation temperature than that of the alpha-mode. On the other hand, the rotational temperature, corresponding to the gas temperature at the atmospheric pressure, were 350 K and 473 K for alpha-and gamma-mode, respectively