Presentation Information
[4Marine-09-KL]Metabolic engineering of marine oleaginous microalgae for biofuel and chemical production
○Tsuyoshi Tanaka1 (1. Tokyo University of Agriculture and Technology (Japan))
Keywords:
oleaginous microalgae
Purpose
A sustainable society requires the development of renewable energy systems that reduce carbon dioxide emissions and mitigate climate change. Among various options, microalgal biofuels have attracted increasing attention due to their high photosynthetic efficiency and ability to convert CO2 into lipids. In particular, oleaginous marine microalgae can accumulate triacylglycerols, which are suitable feedstocks for biofuels. However, large-scale and economically viable production remains a major challenge due to issues such as culture instability, high energy consumption, and process inefficiencies. This study aims to develop robust microalgal strains and cultivation systems through metabolic engineering and process optimization, focusing on the marine diatom Fistulifera solaris as a promising platform for biofuel and biochemical production.
Method
About 1,400 strains were evaluated for growth in seawater and lipid accumulation capacity, leading to the identification of F. solaris as a superior oil-producing strain. We sequenced its whole genome and established a genetic transformation system to enable metabolic engineering. To address bottlenecks in biofuel production, we developed engineered strains targeting key steps in the process. For improving cultivation stability, we introduced chlorophyllase (CLH) into the cytoplasm to generate phototoxic compounds upon predator digestion, thereby conferring resistance against amoebae. For reducing harvesting energy, we engineered strains that enhance flocculation and sedimentation in the presence of silica particles.
Results
F. solaris exhibited exceptional lipid productivity, with oil content reaching up to 65%. The engineered CLH-expressing strains demonstrated strong resistance to amoebae, one of the primary causes of culture collapse in outdoor systems. While wild-type cultures rapidly collapsed in the presence of predators, the engineered strains maintained stable growth, indicating the effectiveness of this biological control strategy. In addition, engineered strains showed improved biomass recovery through enhanced sedimentation in the presence of silica particles. This approach has the potential to significantly reduce energy consumption in the harvesting step. Pilot-scale outdoor cultivation demonstrated the feasibility of large-scale production, achieving oil productivity of up to 18 tons per hectare. Furthermore, metabolic engineering enabled the production of high-value compounds such as docosapentaenoic acid, bisabolene, and prostaglandins. The co-production of these compounds can improve the economic feasibility of biofuel production, addressing a critical barrier to commercialization.
Conclusion
This study demonstrates that F. solaris is a highly promising platform for sustainable biofuel production. By integrating strain development, metabolic engineering, and pilot-scale cultivation, we established a comprehensive approach to address key challenges in microalgal biofuel production.
A sustainable society requires the development of renewable energy systems that reduce carbon dioxide emissions and mitigate climate change. Among various options, microalgal biofuels have attracted increasing attention due to their high photosynthetic efficiency and ability to convert CO2 into lipids. In particular, oleaginous marine microalgae can accumulate triacylglycerols, which are suitable feedstocks for biofuels. However, large-scale and economically viable production remains a major challenge due to issues such as culture instability, high energy consumption, and process inefficiencies. This study aims to develop robust microalgal strains and cultivation systems through metabolic engineering and process optimization, focusing on the marine diatom Fistulifera solaris as a promising platform for biofuel and biochemical production.
Method
About 1,400 strains were evaluated for growth in seawater and lipid accumulation capacity, leading to the identification of F. solaris as a superior oil-producing strain. We sequenced its whole genome and established a genetic transformation system to enable metabolic engineering. To address bottlenecks in biofuel production, we developed engineered strains targeting key steps in the process. For improving cultivation stability, we introduced chlorophyllase (CLH) into the cytoplasm to generate phototoxic compounds upon predator digestion, thereby conferring resistance against amoebae. For reducing harvesting energy, we engineered strains that enhance flocculation and sedimentation in the presence of silica particles.
Results
F. solaris exhibited exceptional lipid productivity, with oil content reaching up to 65%. The engineered CLH-expressing strains demonstrated strong resistance to amoebae, one of the primary causes of culture collapse in outdoor systems. While wild-type cultures rapidly collapsed in the presence of predators, the engineered strains maintained stable growth, indicating the effectiveness of this biological control strategy. In addition, engineered strains showed improved biomass recovery through enhanced sedimentation in the presence of silica particles. This approach has the potential to significantly reduce energy consumption in the harvesting step. Pilot-scale outdoor cultivation demonstrated the feasibility of large-scale production, achieving oil productivity of up to 18 tons per hectare. Furthermore, metabolic engineering enabled the production of high-value compounds such as docosapentaenoic acid, bisabolene, and prostaglandins. The co-production of these compounds can improve the economic feasibility of biofuel production, addressing a critical barrier to commercialization.
Conclusion
This study demonstrates that F. solaris is a highly promising platform for sustainable biofuel production. By integrating strain development, metabolic engineering, and pilot-scale cultivation, we established a comprehensive approach to address key challenges in microalgal biofuel production.
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