Research Progress in Area 4 方向 ( 四 ) 課題進展 197 Abstract Marine microalgae, as the main primary producer of long-chain polyunsaturated fatty acids (LC-PUFA), has a complex lipid metabolism network that needs to be clarified, which involves a variety of competitive or synergistic enzymes and metabolic pathways, and coordination different subcellular compartments, and the lack of cognitive regulatory mechanisms. In order to achieve efficient bio-fabrication of microalgal functional fatty acids, in-depth analysis of the pathways related to microalgal fatty acid synthesis is urgently needed. Therefore, this project will carry out interdisciplinary and cooperative research based on the highly efficient microalgal functional genomics research system and the yeast engineering research platform established in Dr. Carol Lin’s laboratory. We will systematically study the metabolic pathways, enzymes, intracellular transport and regulatory factors related to the accumulation of PUFA in oil-rich microalgae at the molecular level, clarify the relevant pathwaysand their keynodes, and reconstruct the fatty acid metabolism network and regulation model. Then the key enzymes will be improved through directed evolution in the yeast expression system, and a new PUFA biosynthetic pathway will be rationally designed suitable for Yarrowia lipolytica chassis cells, to create high-efficiency engineered yeast strains. Finally, we will design and optimize the fermentation process to establish functional PUFAs biomanufacturing platform. The research results will enhance the scientific cognition in the field of synthesis of active lipid substances, and help the transformation and upgrading of related industries. Research Activities and Progress • Subjected the diatom microalga Phaeodactylum tricornutum to two-factor adaptive evolution to obtain an evolved strain successfully, ALEPt1, with enhanced polyunsaturated fatty acid production capability; • Food waste was used it as a primary negligiblevalue carbon source for ALE-Pt1 cultivation under mixotrophic conditions to improve biomass yield and polyunsaturated fatty acid production; • The ALE-Pt1-based food waste upcycling loop proposed here exemplifies a promising waste valorisation strategy that can produce valuable polyunsaturated fatty acid and biomass (Fig.1). Key Findings • This is the first report on a bioprocess of simultaneous two-factor evolution of P. tricornutum to yield a new strain, namely ALE-Pt1, which is capable of enhanced biomass and PUFA accumulation; • Semi-continuous fermentation of ALE-Pt1 strain using food waste resulted in the production of 7.8 g of biomass and 0.87 g of eicosapentaenoic acid in a 2.8-L culture medium; • Furthermore, a food waste upcycling loop was established that permitted biomass and lipogenic biosynthesis by ALE-Pt1 under conditions of semi-continuous fermentation, resulting in a yield of 7.8 g of biomass and 0.87 g of EPA from a 2.8-L culture volume; • Overall, an excellent microalgal-based technology based on the principle of waste to wealth that can potentially reduce the environmental and health hazards caused by food waste and facilitate microalgal PUFA production based on the principles of circular food waste biorefinery was developed. Research Output Publication 3 Trained personnel 1 Biosynthesis of Long-Chain Polyunsaturated Fatty Acids by Yarrowia lipolytica Fermentation Based on Biosynthetic Pathway of Oleaginous Microalgae Dr. Carol Sze Ki Lin City University of Hong Kong Fig 1.
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