• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.484-488
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• 2006

Alteration of illumination with optimum carbon dioxide fixation-based curve in this research successfully enhanced the $CO_{2}-fixation\;(q_CO_{2}$ capability of Chlorella vulgaris Buitenzorg cultivated in a bubble column photo bioreactor. The level of $CO_{2}$ fixation was up to 1.91 times that observed from cultivation with intensification of illumination on an optimum growth-based curve. During 144 h of cultivation, alteration of light intensity on an optimum $CO_{2}-fixation-based$ curve produced a $q_CO_{2}$ of $12.8\;h^{-1}$. Meanwhile, alteration of light intensity with a growth-based curve only produced a $q_CO_{2}$ of $6.68\;h^{-1}$. Increases in light intensity based on a curve of optimum $CO_{2}-fixation$ produced a final cell concentration of about 5.78 g/L. Both cultivation methods were carried out under ambient pressure at a temperature of $29^{\circ}C$ with a superficial gas velocity of $2.4\;m/h(U_{G}$. Cells were grown on Beneck medium in a 1.0 L Bubble Column Photo bioreactor illuminated by a Phillips Halogen Lamp (20 W/12 V/50 Hz). The inlet gas had a carbon dioxide content of 10%.

• Microbiology and Biotechnology Letters
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• v.47 no.3
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• pp.381-389
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• 2019

Chlorella vulgaris was isolated from the Nile River, Qalubia Governorate, Egypt, for possible use in biodiesel production. BG-II nutrient growth media was used for isolation and laboratory growth. Identification was performed via 18S rRNA gene amplification, followed by sequencing. The alga was exposed to UV-C (254 nm) for 15, 30, and 45 s to improve dry weight accumulation and to increase the oil production. Daily measurements of dry weight ($g{\cdot}l^{-1}$) were performed; oil content and volumetric lipid productivity were also determined. UV-C exposure led to an increase in the volumetric lipid productivity by 27, 27.3, and $32.4mg{\cdot}l^{-1}{\cdot}d^{-1}$ with 15, 30, and 45 s, respectively, as compared with the control, which resulted in $18mg{\cdot}l^{-1}{\cdot}d^{-1}$. Of the examined mutants, the one with the highest productivity was re-irradiated by UV-C (254 nm) for 15, 30, 45, and 60 s. For 15 s of exposure time, the oil content increased to 34%, while it was 31% at 30 s; further, it decreased to 22% at 45 and 60 s exposures. The fatty acid methyl ester profile was 82.22% in the first mutant at 45 s, compared with the wild strain that contained a total of 66.01% of FAs. Furthermore, the highest levels of polyunsaturated fatty acid methyl ester were observed in the mutant exposed for 45 s, and it reached 11.41%, which reduced the cetane number to 71.3.

• Journal of Plant Biology
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• v.36 no.4
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• pp.321-326
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• 1993

Sugar uptake is accompanied with H+-substrate-symport generally. Both H+/sugar-and H+/K+ stoichiometries during the sugar-uptake have been reported to be exactly 1 : 1. This paper reports that the stoichiometries were enhanced dramatically by the addition of CaCl2 into the medium and by the high cell density of 200 $\mu$L pc/mL. The concentration of free Ca2+ ions in the cells increased significantly with cell density. It is suggested that the free Ca2+ ions are responsible for the change of stoichiometry of sugar transport system by regulation of H+ ion level of biomembrane.

• Nutrition Research and Practice
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• v.3 no.1
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• pp.23-30
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• 2009

The aim of this study was to examine the hypoglycemic effect of chlorella in 6 week-old type 2 diabetic Goto-Kakizaki (GK, n=30) rats and 6 week-old normal Wistar (n=30) rats. Animals were randomly assigned to 3 groups respectively, and were fed three different experimental diets containing 0%, 3% or 5% (w/w) chlorella for 8 weeks. In diabetic GK rats, the insulinogenic-indices were not significantly different among the groups. The concentrations of fasting plasma glucagon and hepatic triglyceride, and the insulin/glucagon ratios of the GK-3% chlorella and GK-5% chlorella groups were significantly lower than those of the GK-control group. The HOMA-index and the concentrations of fasting blood glucose and plasma insulin of the GK-3% chlorella and GK-5% chlorella groups were slightly lower than those of the GK-control group. In normal Wistar rats, the insulinogenic-indices were not significantly different among the normal groups, but that of the Wistar-5% chlorella group was slightly higher than the other groups. The concentrations of fasting blood glucose and plasma insulin, and the HOMA-index of the Wistar-5% chlorella group were a little higher, and the fasting plasma glucagon concentration and the insulin/glucagon ratio of the Wistar-5% chlorella group were significantly higher than those of the Wistar-control and Wistar-3% chlorella groups. In conclusion, this study shows that the glucose-stimulated insulin secretion was not affected by the intake of chlorella, which could be beneficial, however, in improving insulin sensitivity in type 2 diabetic GK and normal Wistar rats.

• The Korean Journal of Food And Nutrition
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• v.19 no.2
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• pp.169-175
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• 2006

A unicellular algae, Chlorella vulgaris(CV), was used as a biological response modifier. The effect of CV on forced swimming test and blood biochemical parameters related to fatigue was investigated. Blood urea nitrogen(BUN); creatine kinase(CK); lactic dehydrogenase(LDH); glucose(Glc); total protein(TP); and albumin were determined. CV was orally administered to mice in the range of 0.05 to 0.15 g/kg/day. A forced swimming test results on 3 and 7 day after administration of CV, showed that immobility time was decreased in the CV-administered group(0.15 g/kg). In addition, the contents of BUN in the blood serum were decreased in CV-fed group. The contents of CK and LDH were tended to decrease, but not statistically significant. The plasma Glc level was increased in CV-fed groups(0.05 and 0.1 g/kg) compared to control group. It had no effect on the elevation of TP and albumin level. The results indicate that CV could improve physical stamina.

• Journal of Life Science
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• v.27 no.10
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• pp.1137-1144
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• 2017

The microalgae Chlorella vulgaris has been considered an important alternative resource for biodiesel production. However, its industrial-scale production has been constrained by the low productivity of the biomass and lipid. To overcome this problem, we isolated and characterized a potentially economical oleaginous strain of C. vulgaris via the random mutagenesis technique using UV irradiation. Two types of mass production systems were compared for their yield of biomass and lipid content. Among the several putatively oleaginous strains that were isolated, the particular mutant strain designated as UBM1-10 in the laboratory showed an approximately 1.5-fold higher cell yield and lipid content than those from the wild type. Based on these results, UBM1-10 was selected and cultivated under outdoor conditions using two different types of reactors, a tubular-type photobioreactor (TBPR) and an open pond-type reactor (OPR). The results indicated that the mutant strain cultivated in the TBPR showed more than 5 times higher cell concentrations ($2.6g\;l^{-1}$) as compared to that from the strain cultured in the OPR ($0.5g\;l^{-1}$). After the mass cultivation, the cells of UBM1-10 and the parental strain were further investigated for crude lipid content and composition. The results indicate a 3-fold higher crude lipid content from UBM1-10 (0.3%, w/w) as compared to that from the parent strain (0.1% w/w). Therefore, this study demonstrated that the economic potential of C. vulgaris as a biodiesel production resource can be increased with the use of a photoreactor type as well as the strategic mutant isolation technique.

• Journal of Microbiology and Biotechnology
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• v.16 no.6
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• pp.952-960
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• 2006

As a unicellular green alga that possesses many of the metabolic pathways present in higher plants, Chlorelia offers many advantages for expression of heterologous proteins. Since strong and constitutive promoters are necessary for efficient expression in heterologous expression systems, the development of such promoters for use in the Chlorella system was the aim of this study. Proteins encoded by the early genes of algal viruses are expressed before viral replication, probably by the host transcriptional machinery, and the promoters of these genes might be useful for heterologous expression in Chlorella. In this study, putative promoter regions of DNA polymerase, ATP-dependent DNA ligase, and chitinase genes were amplified from eight Korean Chlorella virus isolates by using primer sets designed based on the sequence of the genome of PBCV-1, the prototype of the Phycodnaviridae. These putative promoter regions were found to contain several cis-acting elements for transcription factors, including the TATA, CAAT, NTBBF1, GATA, and CCAAT boxes. The amplified promoter regions were placed into Chlorella transformation vectors containing a green fluorescence protein (GFP) reporter gene and the Sh ble gene for phleomycin resistance. C. vulgaris protoplasts were transformed and then selected with phleomycin. The GFP fluorescence intensities of cells transformed with chitinase, DNA polymerase, and DNA ligase gene promoter-GFP fusion constructs were 101.5, 100.8, and 95.8%, respectively, of that of CaMV 35S-GFP-transformed Chlorella cells. These results demonstrate that these viral promoters are active in transformed Chlorella.

• Microbiology and Biotechnology Letters
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• v.48 no.4
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• pp.547-555
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• 2020

Microalgae are a promising resource in energy and food production as they are cost-effective for biomass production and accumulate valuable biological resources. In this study, CO2 assimilation, biomass, and lipid production of 4 microalgal species (Chlorella vulgaris, Mychonastes homosphaera, Coelastrella sp., and Coelastrella vacuolata) were characterized at different CO2 concentrations ranging from 1% to 9%. Microscopic observation indicated that C. vulgaris was the smallest, followed by M. homosphaera, C. vacuolata, and Coelastrella sp. in order of size. C. vulgaris grew and consumed CO2 more rapidly than any other species. C. vulgaris exhibited a linear increase in CO2 assimilation (up to 9.62 mmol·day-1·l-1) as initial biomass increased, while the others did not (up to about 3 mmol·day-1·l-1). C. vulgaris, Coelastrella sp., and C. vacuolata showed a linear increase in the specific CO2 assimilation rate with CO2 concentration, whereas M. homosphaera did not. Moreover, C. vulgaris had a greater CO2 assimilation rate compared to those of the other species (14.6 vs. ≤ 11.9 mmol·day-1·l-1). Nile-red lipid analysis showed that lipid production per volume increased linearly with CO2 concentration in all species. However, C. vulgaris increased lipid production to 18 mg·l-1, compared to the 12 mg·l-1 produced by the other species. Thus, C. vulgaris exhibited higher biomass and lipid production rates with greater CO2 assimilation capacity than any other species.

• Microbiology and Biotechnology Letters
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• v.44 no.3
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• pp.400-407
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• 2016

A unicellular green alga, Chlorella vulgaris KNUA027, was isolated from the roots of Panax ginseng seedlings and its biotechnological potential was investigated. The results of GC/MS analysis showed that C. vulgaris KNUA027 was rich in nutritionally important polyunsaturated fatty acids (PUFAs) such as alpha-linolenic acid (C_18:3 ω3, 45.8%, 50.8 mg/g) and hexadecatrienoic acid (C_16:3 ω3, 11.8%, 13.1 mg/g). Therefore, this Korean indigenous microalga may have potential as a source of omega-3 PUFAs. It was also found that the saturated palmitic acid (C_16:0, 37.1%, 41.2 mg/g), which is suitable for biodiesel production, was one of the major fatty acids produced by strain KNUA027. The proximate analysis showed that the volatile matter content was 88.5%, and the ultimate analysis indicated that the higher heating value was 19.8 MJ/kg. Therefore, the results from this research with C. vulgaris KNUA027 may provide the basis for the production of microalgae-based biofuels and biomass feedstock.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.1
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• pp.32-40
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• 2017

The aim of this study was to evaluate a temperature-induced two-stage cultivation (TTC) strategy for the regulation of lipid and carbohydrate production by two microalgae, Chlorella vulgaris and Dunaliella salina, for biofuel production. The microalgae were grown under several temperature conditions (15, 25, 35, and $45^{\circ}C$) and optimal growth was observed at $25^{\circ}C$ for both microalgae. To test the TTC, aseptically cultured microalgae were incubated under optimal conditions ($25^{\circ}C$) for 20 days, and then divided into four aliquots that were incubated at 15, 25, 35, and $45^{\circ}C$ for 5 days. Similar but somewhat decreased growth rates were observed at the non-optimal temperatures (15, 35, and $45^{\circ}C$). In addition, while total lipid accumulation increased in a temperature-dependent manner in both microalgae, total carbohydrate increased with temperature in C. vulgaris but decreased in D. salina. However, for lipid and carbohydrate production, while the highest lipid productions of C. vulgaris and D. salina were observed at $25^{\circ}C$ and $35^{\circ}C$, respectively, the highest total carbohydrate productions of C. vulgaris and D. salina were obtained at $15^{\circ}C$ and $25^{\circ}C$, respectively. These results suggest that the TTC strategy may be easily and efficiently applied to bioprocessing for biofuel production.