Developing the cultivation technology of Asparagopsis taxiformis, potential for methane reduction in livestock

다국어 초록 (Multilingual Abstract)

Global Methane Pledge (GMP) was launched for mitigating anthropogenic CH4 emissions. Among anthropogenic sources, enteric fermentation from ruminants in livestock industry accounts for about 30 % of total anthropogenic CH4 emissions. Feed supplement of Asparagopsis taxiformis gametophyte has emerged as a powerful solution to mitigate CH4 emission from enteric fermentation in ruminant. Thus, interest and biomass demand for A. taxiformis has been increased worldwide. However, current cultivation technique using re-attachment of fragmented wild- harvested gametophyte is not suitable for A. taxiformis due to lack of barbed branches. A protocol using tetraspores reproduced from tetrasporophytes is proposed as a solution. Therefore, the knowledge about environmental conditions for ⅰ) tetrasporophyte cultivation (chapter 2); ⅱ) tetrasporangia formation(chapter 2); ⅲ) tetraspore release and development of juvenile gametophyte(chapter 2); ⅳ) gametophyte cultivation (chapter 3) are required for establishing and scaling up the A. taxiformis gametophyte cultivation. This study evaluated Italian and Korean strains of A. taxiformis to investigate the environmental conditions for tetrasporophyte cultivation and tetrasporangia formation. Light quality affected the growth, photosynthesis and pigment content of A. taxiformis tetrasporophytes Italian strain. The highest growth and photosynthetic activity were observed under blue light, whereas the highest chlorophyll-a and phycoerythrin contents were observed under red light. These results showed that the optimal light quality for growth and pigment contents in A. taxiformis were blue and red light, respectively. Temperature was a key factor in both growth and reproduction, whereas photoperiod was a key factor in reproduction. Growth of tetrasporophyte Italian strain was inhibited by 10 ℃ regardless of photoperiod. The development of tetrasporangia was only observed at 20 ℃ with 8:16 h (L:D). At 20 ℃ with 8:16 h (L:D), the development of tetrasporangia was observed at 20 and 40 μmol photons m-2 s-1 while the highest growth rate was observed at 160 μmol photons m-2 s-1 without development of tetrasporangia, indicating a resource trade-off between growth and reproduction. The Korean strain of tetrasporophytes formed tetrasporangia at specific combination of temperature (22 and 24 ℃) and high nutrient concentration. These results suggested that temperature might be a stronger factor than photoperiod on tetrasporangia formation of A. taxiformis. Additionally, the highest number of released tetraspores and germination rate were observed at 24 ℃. The juvenile gametophytes Korean strain showed the highest number of cells and length at 24 ℃. Similarly, the highest growth was observed at 24 ℃ under the photoperiods of 12:12 and 16:8 h, correlating with the highest photosynthetic efficiency and pigment contents. Conversely, the lowest growth, photosynthetic efficiency and pigment contents were observed at 30 ℃ regardless of photoperiod, indicating that 30 ℃ might be lethal or severely suboptimal temperature for gametophytes. The highest growth rates were observed with the highest net photosynthesis rate, protein and pigment contents at Jack’s Professional (JP) among 7 different nutrient supplement. Trace elements in JP might enhance the growth through enhancement of photosynthesis, pigment and protein synthesis. In summary, these findings provide fundamental knowledge base for cultivation of A. taxiformis tetrasporophytes and gametophytes with environmental conditions for inducing tetrasporangia.

목차 (Table of Contents)

• Abstact i
• Table of Contents ⅳ
• List of Tables ⅴ
• List of Figures ⅵ
• Chapter 1. General Introduction 1
• 1.1. Global methane emission and mitigation strategy 1
• 1.2. Asparagopsis taxiformis 3
• Chapter 2. Tetrasporophyte Cultivation 6
• 2.1. Introduction 6
• 2.2. Materials and Methods 9
• 2.3. Results 20
• 2.4. Discussion 42
• Chapter 3. Gametophyte Cultivation 51
• 3.1. Introduction 51
• 3.2. Materials and Methods 53
• 3.3. Results 61
• 3.4. Discussion 79
• Chapter 4. General Discussion 85
• Chapter 5. General Conclusion 92
• Reference 96
• 국문초록 115
• v