발광다이오드(LED) 파장이 Tetraselmis suecica와 T. tetrathele의 생장과 생화학적 조성에 미치는 영향

Abstract

Microalgae have been used in a wide range of industries such as fisheries sector, food, biofuels, bioplastics and the use of intracellular nutrients. Environmental factors such as temperature, light, pH, salinity and nutrient conditions in microalgae culture conditions affect photosynthesis and productivity. Light condition is a very important factor because microalgae are photosynthetic organisms. In particular, light wavelengths can alter intracellular biochemical composition and content depending on the photosynthetic pigment reactivity of microalgae. In addition, the nutrient concentration required for microalgae varies from species to species, and the nutrient uptake may vary due to changes in light wavelengths. Accordingly, there has been an attempt to increase efficiency by using a light emitting diode(LED) in the mass culture of microalgae. Tetraselmis is used for a live food for rotifer or bivalvia and also used for water purification because its nutrient uptake is higher than reported other species. It is sometimes used instead of chlorella, which is weak in high temperature. However, there was a difference in the reported studies on the optimal light source of Tetraselmis. Therefore, we investigated the growth, biochemical composition and nutrient uptake of T. suecica and T. tetrathele using the wavelength of light emitting diode (LED). First, we investigated the growth rate of T. suecica and T. tetrathele on the variation of irradiance by LED wavelength. As a result, Tetraselmis were highest under red LED. The reason is red wavelengths promoted rapid DNA synthesis and mitosis of microalgae. Therefore, if the red wavelength can use for a light source for mass culture, high density culture can be achieved in a short time. On the other hand, Yellow LED was thought to show low growth rate, but both species showed about 70% of the maximum growth rate and Ks and I0 lower than other wavelengths. Tetraselmis contains chlorophyll b and the absorption spectrum of Tetraselmis showed a higher absorption rate than other microalgae in the yellow wavelength range. Therefore, it is difficult to use the main pigment in the yellow wavelength, but it is considered that the growth is possible using chlorophyll b. Thus, it can be grown to some extent even at the yellow wavelength, and it is considered that the light affinity is better than the red wavelength. Therefore, it is thought that it is advantageous for growth to irradiate yellow wavelength in lag phase, after cultivation and red wavelength in logarithmic growth period. Biochemical compositions in microalgae are commercially available and can be accumulated by stressing through optical wavelengths. In this study, we identified the pigment using LED wavelength. As a result, chlorophyll a and the accessory pigment showed a generally high concentration at the yellow LED. chlorophyll a was 2.8 ～ 3.11 times higher than the fluorescent lamp and 1.8 ～ 2.8 times higher than the red LED. Also, Neoxanthin, Violaxanthin, 19-Hexanoyloxyfucoxanthin, Lutein, Zeaxanthin, and β-carotene showed the highest concentrations at the yellow wavelength. Because during the cell division under stress environmental conditions, the defensive mechanism to absorb light as much as possible acts, and the accumulation rate of the pigment per cell is rather improved. On the other hand, a low pigment content was observed at the fluorescent lamp and the red wavelength, indicating that there was not enough time to accumulate pigment because of rapid cell division. As a result of analysis of carbohydrate, protein and lipid contents by LED wavelength, Tetraselmis showed the highest protein ratio regardless of wavelength. Changes in the contents of each wavelength showed a high accumulation of carbohydrate, protein and lipid at the yellow wavelength. Carbohydrates up to 3.6 times, 2.5 times more protein, 3.5 times more lipid content. It is thought that the accumulation of intracellular biochemical substances is due to a decrease in the rate of cell division at the yellow LED. Decrease in cell division rate leads to changes in cellular chemical composition and enzyme activity as well as protein synthesis, resulting in increased lipid and carbohydrate content. Therefore, biochemical composition of each wavelength is expected to have no accumulation effect at the red wavelength which promoted growth. On the other hand, red, blue, and green wavelengths were used as light sources for biochemical accumulation. However, this experiment showed a high accumulation effect at the yellow wavelength. Especially, β-carotene, which is a pigment component, increased up to 7.8 times. This was higher than the accumulation effect reported previously. This suggests that the yellow wavelength may be more efficient than the wavelength used for the nutrient enrichment Therefore, we propose the use of yellow wavelength as a wavelength for nutrient accumulation in this study. Microalgae use inorganic nutrients, and nitrogen sources exist in various forms. This study used Ammonium and phosphate to determine nutrient uptake rate. As a result, the maximum uptake rate of ammonium and phosphate ware highest at the red LED. The maximum uptake rate of nutrients in T. suecica, T. tetrathele was relatively higher than that of other microalgae, which means that mass culture is possible in a short time. The required nutrient concentration is also different depending on the wavelength of the LED, so this should also be considered. The control of microalgae through light conditions is easier than with water temperature, salinity and nutrient limitation. Among them, the production efficiency can be increased through the irradiance and the wavelength. However, in the case of open culture(open pond), it is difficult to maintain environmental conditions due to seasonal and weather conditions because it is carried out in the outdoor. In addition, because open culture proceeds using sunlight, it is difficult to match the amount of compensation light required for microalgae with the optimum amount of growth light, and thus there are many restrictions for industrial use. In the closed culture system using an artificial light source, it is advantageous that there is no restriction on the environmental change, and it is possible to maximize the economical effect depending on the selective use of the LED. In this study, T. suecica and T. tetrathele showed high growth rate at red wavelength of LED wavelength. However, the yellow wavelength was 70% of the maximum growth rate of the red wavelength and Ks was lower than other wavelengths. The accumulation of pigment, carbohydrate, protein and lipid, which is a biochemical composition, was confirmed under the yellow wavelength. The biochemical composition of microalgae affects the in vivo composition of the communicating larvae and shellfish. This can ultimately provide high nutritional food for humans in the upper nutritional stage. Meanwhile, the present study confirmed that the wavelength for promoting growth and the wavelength for biochemical accumulation were different. In addition, nutrient information required for microalgae can reduce costs by minimizing the concentration of nutrients in mass culture. Therefore, if multi-stage illumination cultivation considering red and yellow mixed wavelength culture and nutrient condition is performed, it can contribute to economical effect and productivity increase. In other words, the yellow LED should be used for rapid growth in the lag phase and the early logarithmic phase, the red LED which shows the maximum growth rate in the mid-logarithmic phase, and the yellow LED for the late phase and the steady-state phase.

Microalgae have been used in a wide range of industries such as fisheries sector, food, biofuels, bioplastics and the use of intracellular nutrients. Environmental factors such as temperature, light, pH, salinity and nutrient conditions in microalgae culture conditions affect photosynthesis and productivity. Light condition is a very important factor because microalgae are photosynthetic organisms. In particular, light wavelengths can alter intracellular biochemical composition and content depending on the photosynthetic pigment reactivity of microalgae. In addition, the nutrient concentration required for microalgae varies from species to species, and the nutrient uptake may vary due to changes in light wavelengths. Accordingly, there has been an attempt to increase efficiency by using a light emitting diode(LED) in the mass culture of microalgae. Tetraselmis is used for a live food for rotifer or bivalvia and also used for water purification because its nutrient uptake is higher than reported other species. It is sometimes used instead of chlorella, which is weak in high temperature. However, there was a difference in the reported studies on the optimal light source of Tetraselmis. Therefore, we investigated the growth, biochemical composition and nutrient uptake of T. suecica and T. tetrathele using the wavelength of light emitting diode (LED). First, we investigated the growth rate of T. suecica and T. tetrathele on the variation of irradiance by LED wavelength. As a result, Tetraselmis were highest under red LED. The reason is red wavelengths promoted rapid DNA synthesis and mitosis of microalgae. Therefore, if the red wavelength can use for a light source for mass culture, high density culture can be achieved in a short time. On the other hand, Yellow LED was thought to show low growth rate, but both species showed about 70% of the maximum growth rate and Ks and I0 lower than other wavelengths. Tetraselmis contains chlorophyll b and the absorption spectrum of Tetraselmis showed a higher absorption rate than other microalgae in the yellow wavelength range. Therefore, it is difficult to use the main pigment in the yellow wavelength, but it is considered that the growth is possible using chlorophyll b. Thus, it can be grown to some extent even at the yellow wavelength, and it is considered that the light affinity is better than the red wavelength. Therefore, it is thought that it is advantageous for growth to irradiate yellow wavelength in lag phase, after cultivation and red wavelength in logarithmic growth period. Biochemical compositions in microalgae are commercially available and can be accumulated by stressing through optical wavelengths. In this study, we identified the pigment using LED wavelength. As a result, chlorophyll a and the accessory pigment showed a generally high concentration at the yellow LED. chlorophyll a was 2.8 ～ 3.11 times higher than the fluorescent lamp and 1.8 ～ 2.8 times higher than the red LED. Also, Neoxanthin, Violaxanthin, 19-Hexanoyloxyfucoxanthin, Lutein, Zeaxanthin, and β-carotene showed the highest concentrations at the yellow wavelength. Because during the cell division under stress environmental conditions, the defensive mechanism to absorb light as much as possible acts, and the accumulation rate of the pigment per cell is rather improved. On the other hand, a low pigment content was observed at the fluorescent lamp and the red wavelength, indicating that there was not enough time to accumulate pigment because of rapid cell division. As a result of analysis of carbohydrate, protein and lipid contents by LED wavelength, Tetraselmis showed the highest protein ratio regardless of wavelength. Changes in the contents of each wavelength showed a high accumulation of carbohydrate, protein and lipid at the yellow wavelength. Carbohydrates up to 3.6 times, 2.5 times more protein, 3.5 times more lipid content. It is thought that the accumulation of intracellular biochemical substances is due to a decrease in the rate of cell division at the yellow LED. Decrease in cell division rate leads to changes in cellular chemical composition and enzyme activity as well as protein synthesis, resulting in increased lipid and carbohydrate content. Therefore, biochemical composition of each wavelength is expected to have no accumulation effect at the red wavelength which promoted growth. On the other hand, red, blue, and green wavelengths were used as light sources for biochemical accumulation. However, this experiment showed a high accumulation effect at the yellow wavelength. Especially, β-carotene, which is a pigment component, increased up to 7.8 times. This was higher than the accumulation effect reported previously. This suggests that the yellow wavelength may be more efficient than the wavelength used for the nutrient enrichment Therefore, we propose the use of yellow wavelength as a wavelength for nutrient accumulation in this study. Microalgae use inorganic nutrients, and nitrogen sources exist in various forms. This study used Ammonium and phosphate to determine nutrient uptake rate. As a result, the maximum uptake rate of ammonium and phosphate ware highest at the red LED. The maximum uptake rate of nutrients in T. suecica, T. tetrathele was relatively higher than that of other microalgae, which means that mass culture is possible in a short time. The required nutrient concentration is also different depending on the wavelength of the LED, so this should also be considered. The control of microalgae through light conditions is easier than with water temperature, salinity and nutrient limitation. Among them, the production efficiency can be increased through the irradiance and the wavelength. However, in the case of open culture(open pond), it is difficult to maintain environmental conditions due to seasonal and weather conditions because it is carried out in the outdoor. In addition, because open culture proceeds using sunlight, it is difficult to match the amount of compensation light required for microalgae with the optimum amount of growth light, and thus there are many restrictions for industrial use. In the closed culture system using an artificial light source, it is advantageous that there is no restriction on the environmental change, and it is possible to maximize the economical effect depending on the selective use of the LED. In this study, T. suecica and T. tetrathele showed high growth rate at red wavelength of LED wavelength. However, the yellow wavelength was 70% of the maximum growth rate of the red wavelength and Ks was lower than other wavelengths. The accumulation of pigment, carbohydrate, protein and lipid, which is a biochemical composition, was confirmed under the yellow wavelength. The biochemical composition of microalgae affects the in vivo composition of the communicating larvae and shellfish. This can ultimately provide high nutritional food for humans in the upper nutritional stage. Meanwhile, the present study confirmed that the wavelength for promoting growth and the wavelength for biochemical accumulation were different. In addition, nutrient information required for microalgae can reduce costs by minimizing the concentration of nutrients in mass culture. Therefore, if multi-stage illumination cultivation considering red and yellow mixed wavelength culture and nutrient condition is performed, it can contribute to economical effect and productivity increase. In other words, the yellow LED should be used for rapid growth in the lag phase and the early logarithmic phase, the red LED which shows the maximum growth rate in the mid-logarithmic phase, and the yellow LED for the late phase and the steady-state phase.