Recently, plant factories are being developed for lower cost and safer food production. The systems can provide some advantages including high yield of crop and efficient use of resources. The waste nutrient solution (WNS) from the plant factory contains nitrogen and phosphorus compounds and their c...
Recently, plant factories are being developed for lower cost and safer food production. The systems can provide some advantages including high yield of crop and efficient use of resources. The waste nutrient solution (WNS) from the plant factory contains nitrogen and phosphorus compounds and their concentrations are approximately 120 mg/L NO3- and 40 mg/L PO43-. Therefore, WNS from the plant factory must be treated appropriately prior to discharge. Microalgae are highly capable of uptaking nitrate and phosphate and one of good candidate microorganisms to treat WNS. Furthermore, LED lights offer several advantages for algal photosynthetic activity over conventional lamps, thereby being considered as the optimal light source for microalgal cultivation. However, algal growth and physiology under LED lights have not been fully understood. For this reason, this thesis focuses on understanding the effect of LED illumination on microalgal growth, physiology, nutrient uptake, and so on. And the development of LED based photo-bioreactor system for WNS treatment from the plant factory by microalgae. The applicability for WNS treatment was verified in this study and the results were as follows:
1. The effect of specific light wavelength on Chlorella vulgaris biology was thoroughly investigated, particularly with red or blue light using molecular tools. qRT-PCR was used to examine the relative expression of these genes under the conditions between white, red, and blue illumination. Based on this discovery, the effect of light wavelengths on microalgal biology, the appropriate wavelength at different growth stages was conceived as a novel strategy for C. vulgaris cultivation.
2. It was confirmed that WNS from the plant factory could support the growth of microalgal species to the similar level those in artificial media. Consequently, microalgae absorb nitrate and phosphate to increase their biomass. Biomass production and nutrients decrease showed the same trend. Also, one of the microalgae (Acutodesmus bernardii) species was isolated from the plant factory and the confirmation was made through BLAST analysis.
3. Preferred blue to red wavelength ratio varied by microalgae species. Specifically, the highest biomass production attained at 3:1 and 1:3 in A. bernardii and Hamatococcus pluvialis. It was at 15% more efficient than using fluorescent lamps for microalgal biomass production.
4. Using the culture method developed by the LED light source to purify the WNS from the plant factory. The nutrient removal efficiency was also compared three types of microalgae. While the Chlorella vulgaris was the highest biomass productivity, nitrogen and phosphate removal rate were the highest in A. bernardii.
5. Base on the results of the light wavelengths and microalgal biomass production, photobioreactor with internal LED light source was designed for nutrient removal from the plant factory. It was operated 31 days at the plant factory using the C. vulgaris. During the period, WNS was purified at 185 liters and microalgal biomass was produced at 267.8gram.
6. In addition, LED light wavelength applied during the microalgae culture was also a significant factor for harvesting. Because specific wavelengths, such as 660 (red) or 450 nm (blue) could change microalgae cell size, different settlements were found according to wavelength. It was proven that LED light influenced in microalgae culture system not only increased biomass production but also decreased harvesting cost.
This study will shed light on a novel approach using LED light for microalgal biotechnology. Also, it will offer helpful solution for treatment waste nutrient solution in the plant factory.
Recently, plant factories are being developed for lower cost and safer food production. The systems can provide some advantages including high yield of crop and efficient use of resources. The waste nutrient solution (WNS) from the plant factory contains nitrogen and phosphorus compounds and their concentrations are approximately 120 mg/L NO3- and 40 mg/L PO43-. Therefore, WNS from the plant factory must be treated appropriately prior to discharge. Microalgae are highly capable of uptaking nitrate and phosphate and one of good candidate microorganisms to treat WNS. Furthermore, LED lights offer several advantages for algal photosynthetic activity over conventional lamps, thereby being considered as the optimal light source for microalgal cultivation. However, algal growth and physiology under LED lights have not been fully understood. For this reason, this thesis focuses on understanding the effect of LED illumination on microalgal growth, physiology, nutrient uptake, and so on. And the development of LED based photo-bioreactor system for WNS treatment from the plant factory by microalgae. The applicability for WNS treatment was verified in this study and the results were as follows:
1. The effect of specific light wavelength on Chlorella vulgaris biology was thoroughly investigated, particularly with red or blue light using molecular tools. qRT-PCR was used to examine the relative expression of these genes under the conditions between white, red, and blue illumination. Based on this discovery, the effect of light wavelengths on microalgal biology, the appropriate wavelength at different growth stages was conceived as a novel strategy for C. vulgaris cultivation.
2. It was confirmed that WNS from the plant factory could support the growth of microalgal species to the similar level those in artificial media. Consequently, microalgae absorb nitrate and phosphate to increase their biomass. Biomass production and nutrients decrease showed the same trend. Also, one of the microalgae (Acutodesmus bernardii) species was isolated from the plant factory and the confirmation was made through BLAST analysis.
3. Preferred blue to red wavelength ratio varied by microalgae species. Specifically, the highest biomass production attained at 3:1 and 1:3 in A. bernardii and Hamatococcus pluvialis. It was at 15% more efficient than using fluorescent lamps for microalgal biomass production.
4. Using the culture method developed by the LED light source to purify the WNS from the plant factory. The nutrient removal efficiency was also compared three types of microalgae. While the Chlorella vulgaris was the highest biomass productivity, nitrogen and phosphate removal rate were the highest in A. bernardii.
5. Base on the results of the light wavelengths and microalgal biomass production, photobioreactor with internal LED light source was designed for nutrient removal from the plant factory. It was operated 31 days at the plant factory using the C. vulgaris. During the period, WNS was purified at 185 liters and microalgal biomass was produced at 267.8gram.
6. In addition, LED light wavelength applied during the microalgae culture was also a significant factor for harvesting. Because specific wavelengths, such as 660 (red) or 450 nm (blue) could change microalgae cell size, different settlements were found according to wavelength. It was proven that LED light influenced in microalgae culture system not only increased biomass production but also decreased harvesting cost.
This study will shed light on a novel approach using LED light for microalgal biotechnology. Also, it will offer helpful solution for treatment waste nutrient solution in the plant factory.
Keyword
#the plant factory microalgae waste nutrient solution waste recycling LED
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