• Journal of Microbiology and Biotechnology
• /
• v.10 no.6
• /
• pp.817-822
• /
• 2000

A proper flashing light is expected to enhance microalgal biomass productivity and photosynthetic efficiency. The effect of flashing light on high-density Chlorella kessleri (UTEX 398) cultures was studied using light-emitting diodes. A frequency modulator was designed to flash LEDs, and the device successfully provided wide range of frequencies and various duty cycles of flashing. A relatively high frequencies of 10, 20 and 50 kHz were used in this study. These frequencies have very short flashing time ($2-50{\mu}s$), which corresponded to the time constant of the light reaction of photosynthesis. The specific oxygen production rates of photosynthesis under flashing light were compared with those under an equivalent continuous light in specially designed illumination cuvette. The specific oxygen production rates under flashing light were 5-25% higher than those under the continuous light. A range of cell concentration was discovered, where the benefit of flashing light was maximized. The photosynthetic efficiency was also higher under flashing light with frequencies of over 1 kHz, which was a clear indication of flashing light effect and the degree of mutual shading could by overcome by flashing lights, particularly at high-density algal cultures.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.5
• /
• pp.689-694
• /
• 2006

We investigated the potential use of various carbon sources (fructose, glucose, mannose, lactose, and glycerol) for culturing Phaeodactylum tricornutum UTEX-640 in mixotrophic and heterotrophic batch cultures. Concentrations of carbon substrates tested ranged from 0.005 M to 0.2 M. P. tricornutum did not grow heterotrophically on any of the C-sources used, but successive additions of organic carbon in mixotrophic growth mode substantially increased the biomass concentration and productivity relative to photoautotrophic controls. The maximum biomass productivities in mixotrophic cultures for glycerol, fructose, and glucose were 21.30 mg/l h, 15.80 mg/l h, and 10.20 mg/l h, respectively. These values were respectively 10-, 8-, and 5-fold higher than those obtained in the corresponding photoautotrophic control cultures. Mannose and lactose did not significantly affect microalgal growth. The biomass lipids, eicosapentaenoic acid (EPA) and pigments contents were considerably enhanced with glycerol and fructose in relation to photoautotrophic controls. The EPA content was barely affected by the sugars, but were more than 2-fold higher in glycerol-fed cultures than in photoautotrophic controls.

• Journal of Microbiology and Biotechnology
• /
• v.12 no.6
• /
• pp.979-985
• /
• 2002

The possibility of microalgal nitrogen treatment was tested in wastewaters with a low carbon/nitrogen (C/N) ratio. Chlorella kessleri was cultured in the two different artificial wastewaters with nitrate as a nitrogen source: one contained glucose for an organic carbon source and the other without organic carbon sources. The growth rates of the two cultures were almost identical when the aeration rate was over 1 vvm. These results suggest that microalgae could successfully remove nitrogen from wastewater, as far as the mass transfer of $CO_2$, was not limited. Nitrate was successfully reduced to below 2 mg $NO_3^-$-N/ml from the initial nitrate concentration of 140 mg $NO_3^-$-N/ml in 10 days, even in the wastewater with no organic carbon source. Similar results were obtained when ammonium was used as the sole nitrogen source instead of nitrate. Higher concentrations of nitrogen of 140, 280, 560 and 1,400 mg/ml were also tested and similar amounts of nitrogen were removed by algal cultures without showing any substrate inhibition.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.2
• /
• pp.125-132
• /
• 2011

This paper describes current status and future prospects of the mass production of microalgae biomass. Microalgae have attracted considerable attention since they not only effectively fix $CO_2$ gas during their metabolic process but also have the great potential to be utilized for producing valuable substances as a kind of efficient light-harvesting cell factories. In this review, we outline various types of photobioreactors employed for mass production of biomass by culturing microalgae in a well controlled way and give an overview about the present state of affairs, both domestic and international, in the field of the microalgal culturing technologies.

• Applied Chemistry for Engineering
• /
• v.29 no.1
• /
• pp.1-9
• /
• 2018

Microalgae is considered as one of environmentally sustainable and potential feedstocks to produce biodiesels. However, recent studies on life cycle assessments (LCA) of microalgal buidiesels have shown that energy requirement is not small to produce biodiesel from microalgae, especially during cultivation stage. The costs for carbon sources, nutrients like nitrogen or phosphorous, and water for cultivation can contribute up to 80% of the total medium costs. In the present article, recent trends on the utilization of several promising nutrient sources such as municipal wastewaters, organic fertilizers, combustion exhaust emissions and organic solid wastes were reviewed, and the potential strategies to be used as substitutes of artificial culture media, especially for the biodiesel production, were discussed.

• Korean Journal of Environmental Biology
• /
• v.38 no.2
• /
• pp.216-221
• /
• 2020

A eukaryotic marine microalga was isolated from Jungmun Saekdal Beach, Jeju Island, Korea and an integrated approach, including molecular phylogeny and morphology, was used to determine its taxonomical status. Molecular phylogenetic evidence inferred from the small subunit (SSU) 18S rRNA sequence and internal transcribed spacer (ITS) secondary structure analysis clearly showed that the isolate belonged to the recently described species, Jaagichlorella roystonensis. Distinctive morphological keys of the species were also observed by light microscopy and scanning/transmission electron microscopy(S/TEM). In this study, a Korean marine J. roystonensis species was described for the first time and was subsequently added to the national culture collections in Korea.

• Journal of Microbiology and Biotechnology
• /
• v.26 no.12
• /
• pp.2066-2075
• /
• 2016

In this study, an enhanced lipid-producing mutant strain of the microalga Chlamydomonas reinhardtii was developed by gamma irradiation. To induce the mutation, C. reinhardtii was gamma irradiated at a dose of 400 Gy. After irradiation, the surviving cells were stained with Nile red. The mutant (Cr-4013) accumulating 20% more lipid than the wild type was selected. Thin-layer chromatography revealed the triglyceride and free fatty acid contents to be markedly increased in Cr-4013. The major fatty acids identified were palmitic acid, oleic acid, linoleic acid, and linolenic acid. Random amplified polymeric DNA analysis showed partial genetic modifications in Cr-4013. To ascertain the changes of protein expression in the mutant strain, two-dimensional electrophoresis was conducted. These results showed that gamma radiation could be used for the development of efficient microalgal strains for lipid production.

• Journal of Korean Society of Water and Wastewater
• /
• v.27 no.6
• /
• pp.703-709
• /
• 2013

Among many microalgae cultivation types, heterotrophic culture with low cost carbon sources and energy saving culture method is crucial. A result of estimating the effects of pH on wastewater treatment using heterotrophic growing microalgae Chlorella sorokiniana shows that there was no difference in microalgae growth amount and nitrogen, phosphorus removal rate by wide range of pH(5 ~ 9). From pH 5 to 9, total nitrogen, phosphorous and glucose removal rates were 10.5 mg-N/L/d, 2 mg-P/L/d, 800 ~ 1000 mg/L respectively. This study reveals that C. sorokiniana cannot metabolite glycerol heterotrophically, however, glucose and acetate were proper carbon sources for growth and T-N, T-P and TOC removal. This research highlights the potential of heterotrophic microalgal growth with wastewater treatment plant with wide range of pH and carbon sources.

• Applied Chemistry for Engineering
• /
• v.21 no.3
• /
• pp.243-251
• /
• 2010

Nitrogen oxides (NOx) in combustion flue gas are currently mitigated by chemical processes such as catalytic reduction, absorption and adsorption. However, development of environmentally sustainable biological processes is necessary in the near future. In this paper, the up-to-dated R&D trend of biological methodologies regarding NOx removal was reviewed, and their advantages and disadvantages were discussed. The principles and applications of bacterial system including nitrification and denitrification and photosynthetic microalgae system were compared. In order to enhance biological treatment rate and performance, the insoluble nitric oxide (NO) should be first absorbed using a proper solubilization agent, and then microbial degradation or fixation is to be followed. The use of microalgal system has a good prospect because it can fix $CO_2$ and NOx simultaneously and requires no additional carbon for energy source.

• Korean Chemical Engineering Research
• /
• v.56 no.5
• /
• pp.773-778
• /
• 2018

In-situ transesterification of microalgae lipids using microwave irradiation has potential to simplify and accelerate biodiesel production, as it minimizes production cost and reaction time by direct transesterification of microalgae into biodiesel with microwave as a heating source. This study was conducted to research the effect of microwave irradiation with in-situ transesterification of microalgae under base catalyst condition. The process variables (reaction time, solvent ratio, microwave power) were studied using 2% of catalyst concentration. The maximum yield of FAME was obtained at about 32.18% at the reaction time of 30 min with biomass-methanol ratio 1:12 (w/v) and microwave power of 450 W. The GC MS analysis obtained that the main component of FAME from microalgal oils (or lipids) was palmitic acid, stearic acid and oleic acid. The results show that microwaves can be used as a heating source to synthesize biodiesel from microalgae in terms of major components resulting.