Alteration of Wax Ester Content and Composition in Euglena gracilis with Gene Silencing of 3‐ketoacyl‐CoA Thiolase Isozymes

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.     

Adhesion Analysis Considering van der Waals Force in a NanoSized Region Using the Boundary Element Method

Recently, micro- and nanomachines for microelectromechanical systems and the mechanism of bio-adhesive pads have attracted great interest. Nanoscale structures are affected by forces such as the van der Waals force, even though they are neglected in large-scale structures. In this paper, the van der Waals force is introduced to a boundary element method (BEM) program for analyzing adhesion in arbitrarily shaped bodies. The van der Waals force is described by a nonlinear function of the distance between two surfaces in close proximity, and the adhesion and repulsion forces vary greatly within the atom equilibrium distance. Therefore, it is difficult to obtain a solution for the simultaneous equation in the BEM. We propose a method to compute the body deformation and apply it to the adhesion between a cylinder and a flat, rigid substrate. The solution is compared with previously published theoretical results, and the validity of the algorithm for approaching the solution is demonstrated. Further calculations for the adhesive contact of softer and harder cylinders with a rigid substrate are conducted.