KR100470060B1 - Culturing method of micro-algae with high contents of fatty acids by using steelmaking slag - Google Patents

Abstract

A method for culturing high fatty acid-containing microalgae using steelmaking slag

The microalgal culture medium is provided with a microalgal culture method of supplying hot water at 2.7-25 g / L of steelmaking slag, 1-10% V / V of carbon dioxide, and 16-24 ° C., and culturing under a light source. This is an economical and environmentally friendly microalgae cultivation method in which steelmaking slag can be used as a nutrient for microalgae in microalgae culture to cultivate microalgae containing high fatty acids useful for human body.

Description

CULTURING METHOD OF MICRO-ALGAE WITH HIGH CONTENTS OF FATTY ACIDS BY USING STEELMAKING SLAG}

The present invention relates to a method for culturing microalgae, and more particularly, to a method for culturing microalgae containing high fatty acid using steelmaking slag.

Microalgae live in fresh or sea water and are single-celled plants without roots, stems and leaves. They are photosynthetic with chlorophyll and contain vegetable fatty acids, proteins, minerals and various vitamins, which are useful for humans. In general, in order to cultivate microalgae, nutrients including a carbon source and a trace element that facilitate the photosynthesis during growth to help proliferation are separately supplied. In addition, hot water is required to control the proper temperature required for somatic cell growth and reproduction of microalgae.

Meanwhile, steel slag discharged from steel mills is a by-product generated from the process of refining pig iron in converters to remove impurities such as carbon, phosphorus, and sulfur. Is required. Currently, some of the steelmaking slag is known to be used as cement raw material, lower layer subgrade material for paint, civil engineering materials and port work materials, but still a large amount of steelmaking slag is not recycled and disposed of. In addition, the steelmaking slag contains microelements suitable for culturing microalgae such as iron, silicon, and sulfur, but a method of culturing microalgae using steelmaking slag has not been developed.

Accordingly, an object of the present invention is to provide a method for culturing microalgae containing a large amount of useful fatty acids using steelmaking slag.

1 is a schematic diagram of the overall culture system used for microalgal culture according to the present invention

Figure 2 is a graph showing the change in the number of cells of microalgae according to the water temperature change,

Figure 3 is a graph showing the change in the number of cells of the algae with or without the addition of steelmaking slag,

Figure 4 is a graph showing the change in the number of cells of microalgae according to the change of carbon dioxide injection amount,

Figure 5 is a graph showing the pH change when the carbon dioxide is injected in the state of the addition of steelmaking slag in microalgae culture in the present invention,

Figure 6 shows the microalgal cell density change when the injection of steelmaking slag, flue gas, warm drainage during microalgal culture in the present invention.

Explanation of symbols on the main parts of the drawings

One… Culture tank 2... Hot water inlet

3... Hot water outlet 4. Steel slag

5... Carbon dioxide injection unit 6. CO2 Bubble

7... sunlight

According to the invention,

The microalgal culture medium is provided with a microalgal culture method of supplying hot water at 2.7-25 g / L of steelmaking slag, 1-10% V / V of carbon dioxide, and 16-24 ° C., and culturing under a light source.

Hereinafter, the present invention will be described in detail.

In the present invention, in culturing the microalgae, the conditions necessary for the growth and propagation of the microalgae are maximized to maximize the growth rate of the microalgae and the useful fatty acid content in the microalgae. In addition, waste resources are recycled by using steelmaking slag, carbon dioxide flue gas, and warm wastewater discharged from power plants for the cultivation of microalgae.

1 is a view showing the overall culture system used for the culture of microalgae according to the present invention. As shown in FIG. 1, steelmaking slag, hot water, and carbon dioxide are introduced into the microalgae culture system in an optimal amount to incubate the microalgae.

Steelmaking slag is included in the microalgal culture medium. Steelmaking slag is a by-product of the steelmaking operation and contains a large amount of various trace elements, so it is supplied as a nutrient for microalgae in microalgae culture. That is, when steelmaking slag is added to the medium, various trace elements such as Fe, CaO, SiO ₂ , Al ₂ O ₃ , MgO, P ₂ O ₅ , S and TiO ₂ are eluted and dissolved in the medium. It is ingested in the body to promote the growth and proliferation of microalgae and photosynthesis of microalgae. In addition, the steelmaking slag serves to prevent the pH decrease that occurs when the carbon dioxide content in the culture water increases, thereby maintaining a proper pH for the growth of microalgae. Suitable pH for microalgal culture is 7-9.

Therefore, steelmaking slag can not only act as a suitable nutrient source for microalgae cultivation, but also has an economical and environmentally friendly advantage in terms of recycling waste.

Steelmaking slag is supplied to the microalgal culture medium at 2.7-25 g / L based on the culture water volume. When steelmaking slag is added at less than 2.7g / L, the culture efficiency is lowered because it does not prevent the decrease of pH due to carbon dioxide injection into the medium.When it is added at 25g / L or more, the pH of the culture water rises to 9 or more. In addition, the culture efficiency is lowered.

Carbon dioxide works to facilitate the photosynthesis of microalgae. Microalgae is a single cell type of plant that needs carbon dioxide, a carbon source necessary for photosynthesis. Generally, some amount of carbon dioxide is present in water, but a separate carbon dioxide is supplied to further promote photosynthesis of microalgae. Carbon dioxide is supplied to the microalgal culture medium as air having 1-10% V / V of the carbon dioxide content in the air. When the carbon dioxide content is lowered to less than 1V%, the microalgae do not grow well because of poor photosynthesis. In addition, if a large amount of carbon dioxide is supplied, the carbon dioxide saturation in the culture water is too large and the oxygen concentration is low, so the culture efficiency is lowered, which is not preferable. Carbon dioxide may be used in any form of carbon dioxide. For example, the carbon dioxide may be carbon dioxide contained in exhaust gas such as carbon dioxide in exhaust gas generated after fossil fuel.

In addition, hot water must be supplied so that the algae grow and grow. Microalgae generally have a property of proliferating well at around 20 ° C., so it is necessary to appropriately control the temperature of the medium. Hot water supplied to the medium may be introduced and discharged at a constant flow rate in any way. For example, hot water can be supplied to or discharged from the medium through a tube whose flow rate can be adjusted. The medium temperature is preferably adjusted to 16-24 ℃ to allow the microalgae to breed well. The hot water introduced into the medium may be warm wastewater and warm water drainage, as long as it is not harmful to the microalgae. For example, the hot water may be supplied to the medium by recycling the hot water discharged from the power plant.

Lastly, the microalgae are cultured by leaving the medium containing steelmaking slag and carbon dioxide as described above and controlled so that hot water is introduced and discharged at a constant flow rate under an appropriate light source. When the medium is left under an appropriate light source, the microalgae contained in the medium more effectively photosynthesize, grow and culture, and synthesize various fatty acids in somatic cells. The step of leaving the medium under a light source may be performed at any stage of the invention, such as, for example, at the same time as the hot water is adjusted to enter and exit the medium at a constant flow rate. Light sources suitable for the present invention also include artificial light such as fluorescent and incandescent and natural light such as sunlight.

As an example of the present invention, as shown in Figure 1, microalgae using a continuous flow culture tank system that allows the power plant on-water drainage inflow 2 , and outlet 3 as a culture water in the culture tank 1 under a solar source 7 Incubate. Culture tank 1 the lower part sinks to spray the slag 4 of size 5-10 mm, and injecting the carbon dioxide off-gas 5 to be such that the carbon dioxide bubbles generated in the water tank 6 can be in culture. In the culture tank 1 and the warm drainage outlet 3 , a 1 μm mesh net is installed to prevent the microalgae from being cultured. In addition, it is possible to control the mixing ratio of the injected carbon dioxide and air using a flow meter to maintain a constant carbon dioxide concentration at a low concentration by mixing with air in the air during carbon dioxide injection.

Microalgae suitable for the present invention include, but are not limited to, Chlorella, such as Chlorella ellipsoidea , Phaeodactylum triconutum , Spirulina platensis , and Kaetocerose . Calcicelan ( Chaetoceros calcitrans ) and Isochysis galbana ( Isochysis galbana ) and the like, in particular, chlorella can be effectively grown and cultured.

Hereinafter, the present invention will be described in detail through examples.

Example

In an embodiment of the present invention, the effect test was conducted on the marine microalgae Chlorella ellipsoidea in order to increase the cultivation capacity and high value of the microalgae .

Example 1 Effect of Water Temperature Change on the Growth of Microalgae

This example is a preliminary experiment confirming the effect of the water temperature change on the growth of chlorella, and does not supply additional steelmaking slag and carbon dioxide, but only changes the temperature of the supplied water to demonstrate the effect of water temperature on the growth of microalgae. will be. In a 250 ml Erlenmeyer flask used as a culture vessel, 150 ml of culture water (general seawater filtered through a 1 μm filter) was used, and the illuminance was 4,000 lux using a fluorescent lamp. The water temperature was 16 ° C., 20 ° C., 24 ° C., 28 ° C., and Each was incubated at 32 ° C. for 7 days. The results are shown in FIG.

As shown in FIG. 2, the highest cell number was 6.5 × 10 6 cells / ml at 7 days of culture at 20 ° C., and 0.9 × 10 6 cells / ml, 0.2 at day 1 of culture at 28 ° C. and 32 ° C. It tends to be lowered to × 10 6 cells / ml. Therefore, the optimum growth water temperature of chlorella was determined to be around 20 ° C. The optimum growth water temperature of chlorella is almost similar to the discharge water temperature of the power plant wastewater, which means that the wastewater can be directly used for mass cultivation.

Example 2-Cultivation of microalgae with or without steelmaking slag

This example is a preliminary experiment to confirm the effect of the addition of steelmaking slag to the culture of chlorella, and cultured the microalgae with and without addition of steelmaking slag without supplying additional carbon dioxide. As a culture tank, a 20 L cylindrical acrylic bath (15 L culture water) was used. The illuminance was 3,000 lux using a fluorescent lamp and the culture temperature was 21 ± 1 ° C., and 500 g of steelmaking slag was added to incubate the microalgae for 6 days. In another tank, microalgae were cultured under the same conditions as above except that no steelmaking slag was added.

As shown in FIG. 3, the cell density in the culture bath to which the steelmaking slag was added was found to be 5.4 × 10 ⁶ cell / ml, which is higher than the cell density of 3.5 × 10 ⁶ cell / ml of the control without the steelmaking slag. This is believed to be due to the fact that various inorganic ions eluted from slag, especially Fe and Si, promoted photosynthesis and cell growth of microalgae, and it can be seen that the cultivation efficiency can be nearly doubled by supplying a small amount of steelmaking slag. .

Example 3-Cultivation of microalgae with or without carbon dioxide

This example is a preliminary experiment for testing the degree of culturing chlorella according to the supply of carbon dioxide, microalgae were incubated by varying the amount of carbon dioxide without adding a steelmaking slag. The culture tank is a 20 liter cylindrical acrylic tank (15 liter culture), the illuminance is 3,000 lux using fluorescent lamps, and the incubation temperature is 21 ± 1 ℃, and the carbon dioxide is 0, 1, 2, 3, 5, 10% (V / V) of the mixed feed was incubated for 6 days. In addition, another tank was cultured under the same conditions as described above except that carbon dioxide was not separately supplied as a standard example.

As shown in Figure 4, it can be seen that the cell density was much increased in the test zone injected with carbon dioxide compared to the standard example without the supply of carbon dioxide. When carbon dioxide was added in an amount limited in the present invention and cultured for 5 days, the maximum cell number was shown, and the control group had a low cell density of 3.5 × 10 ⁶ cells / ml.

Example 4 Investigation of the Effect of Steelmaking Slag on pH

In addition, the pH of the medium was measured in Example 3. At 5 days of culture, the pH of the medium decreased slightly to 7.2 and 7.1, respectively, and at 6 days of culture, the pH decreased to pH 6.7 and 6.6, respectively, and the number of cells decreased significantly. It was. This is believed to be due to the drop in pH of the culture water below the optimum pH for microalgal culture due to the continuous supply of carbon dioxide.

Therefore, pH was adjusted by adding 500 g of steelmaking slag to the conditions of Example 3, and the results are shown in FIG. As a standard example, pH was measured when steelmaking slag and carbon dioxide were not supplied.

As shown in FIG. 5, when 500 g of steelmaking slag and 2% of carbon dioxide (V / V) were fed to the medium, the pH of the medium did not decrease despite the continuous supply of carbon dioxide.

Therefore, by adding steelmaking slag to the medium, it is possible to prevent the pH decrease of the medium by the continuous supply of carbon dioxide.

Example 5 Mass Culture of Chlorella

Chlorella was cultivated outdoors by the method of the present invention.

The culture tank is a 2ton round tank (cultured 1.5ton), the illuminance used natural sunlight, and the continuous flow of the hot water discharged from the power plant with a water temperature of 20 ° C at a constant rate, while CO2 was released on the basis of 10ℓ / min of air. Respectively, the mixtures were supplied at the norm, 1, 3, 5, and 10% (V / V). 4 kg of steel slag was added to each experimental section.

The results are shown in FIG.

In addition, Table 1 shows the results of analyzing the fatty acid content in the microalgal somatic cells cultured by the method according to the present invention (Example 5). Compared with the comparative example without the injection of carbon dioxide, when the carbon dioxide is supplied, it can be seen that a particularly high value-added useful fatty acid content such as EPA and DHA increases significantly.

fatty acid CO ₂ (V / V) One% 3% 5% 10% Comparative Example (0%) Caprylic acid C _{8: 0} 0.22 0.26 0.20 0.24 0.05 Capric acid C _{10: 0} 0.12 0.14 0.12 0.12 0.06 Lauric acid C _{12: 0} 0.20 0.23 0.21 0.25 0.32 Myristic acid C _{14: 0} 2.63 2.70 2.33 2.49 4.75 Pentadecanoic acid C _{15: 0} 0.15 0.17 0.14 0.15 0.39 Palmitic acid C _{16: 0} 10.34 10.58 11.24 12.32 24.46 Palmitoleic acid C _{16: 1} 18.89 19.35 18.83 19.80 17.29 Palmitolenic acid C _{16: 2} 2.24 2.31 1.90 2.13 0.45 Magaric acid C _{17: 0} 0.11 0.12 0.14 0.13 0.64 Margaoleic acid C _{17: 1} 0.34 0.36 0.35 0.52 0.35 Stearic acid C _{18: 0} 0.34 0.25 0.23 0.20 1.10 Oleic acid C _{18: 1} 3.45 3.95 4.34 4.18 8.35 Linoleic acid C _{18: 2} 3.16 3.17 2.55 2.13 4.25 Linolenic acid C _{18: 3} 0.42 0.41 0.23 0.25 0.11 Stearidonic acid C _{18: 4} 0.16 0.16 0.09 0.09 0.12 Arachidonic acid C _{20: 4} 6.12 6.08 7.22 6.94 3.20 EPA C _{20: 5} 44.03 42.82 42.11 39.03 28.46 DPA C _{22: 5 n3} 0.08 0.06 0.58 0.39 0.15 DHA C _{22: 6 n3} 0.19 0.13 0.29 0.18 0.14 Other unidentified substances 6.81 6.75 6.90 8.46 5.36

The supply of steelmaking slag and carbon dioxide according to the present invention improves the cultivation and growth of microalgae and at the same time improves the nutrition of microalgae.

Claims (4)

Microalgae culturing method of supplying hot water of steelmaking slag 2.7-25g / L, carbon dioxide 1-10% V / V and 16-24 ℃ to the microalgae culture medium and incubated under a light source. The method of claim 1 wherein the carbon dioxide source is exhaust gas. The method of claim 1, wherein the hot water is hot water discharged from a power plant. According to claim 1 to 3, any one of, wherein the microalgae is IDEA (Chlorella ellipsoidea) El Chlorella ellipsometer, par ohdak tilreom tree corner Terme (Phaeodactylum triconutum), Spirulina flash tennis (Spirulina platensis), Chitose in South Los calcineurin trans Chaetoceros calcitrans and Isochysis galbana .