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Alteration of Wax Ester Content and Composition in Euglena gracilis with Gene Silencing of 3-ketoacyl-CoA Thiolase Isozymes
- Nakazawa, Masami, Andoh, Hiroko, Koyama, Keiichiro, Watanabe, Yomi, Nakai, Takeo, Ueda, Mitsuhiro, Sakamoto, Tatsuji, Inui, Hiroshi, Nakano, Yoshihisa, Miyatake, Kazutaka
- Lipids 2015 v.50 no.5 pp. 483-492
- Euglena gracilis, adenosine triphosphate, beta oxidation, biodiesel, carbon, databases, expressed sequence tags, fatty acids, fermentation, fluid mechanics, gene silencing, isozymes, melting point, mitochondria, oxidative stability
- Euglena gracilis produces wax ester under hypoxic and anaerobic culture conditions with a net synthesis of ATP. In wax ester fermentation, fatty acids are synthesized by reversing beta-oxidation in mitochondria. A major species of wax ester produced by E. gracilis is myristyl myristate (14:0-14:0Alc). Because of its shorter carbon chain length with saturated compounds, biodiesel produced from E. gracilis wax ester may have good cold flow properties with high oxidative stability. We reasoned that a slight metabolic modification would enable E. gracilis to produce a biofuel of ideal composition. In order to produce wax ester with shorter acyl chain length, we focused on isozymes of the enzyme 3-ketoacyl-CoA thiolase (KAT), a condensing enzyme of the mitochondrial fatty acid synthesis pathway in E. gracilis. We performed a gene silencing study of KAT isozymes in E. gracilis. Six KAT isozymes were identified in the E. gracilis EST database, and silencing any three of them (EgKAT1-3) altered the wax ester amount and composition. In particular, silencing EgKAT1 induced a significant compositional shift to shorter carbon chain lengths in wax ester. A model fuel mixture inferred from the composition of wax ester in EgKAT1-silenced cells showed a significant decrease in melting point compared to that of the control cells.