Genome engineering of E. coli for improved styrene production.

Microbial production of exogenous organic compounds is challenging as biosynthetic pathways are often complex and produce metabolites that are toxic to the hosts. Biogenic styrene is an example of this problem, which if addressed could result in a more sustainable supply of this important component of the plastics industry. In this study, we engineered Escherichia coli for the production of styrene. We systematically optimized the production capability by first screening different pathway expression levels in E. coli strains. We then further designed and constructed a transcription regulator library targeting 54 genes with 85,420 mutations, and tested this library for increased styrene resistance and production. A series of tolerant mutants not only exhibited improved styrene tolerance but also produced higher styrene concentrations compared to the parent strain. The best producing mutant, ST05 LexA_E45I, produced a 3.45-fold increase in styrene compared to the parent strain. The produced styrene was extracted via gas stripping into dodecane and used in a direct free radical synthesis of polystyrene.

Mechanical evaluation of 3D printed biomimetic non-Euclidean saddle geometries mimicking the mantis shrimp.

Engineering design has drawn inspiration from naturally occurring structures to advance manufacturing processes and products, termed biomimetics. For example, the mantis shrimp, orderStomatopoda, is capable of producing one of the fastest appendage strikes in the world with marginal musculoskeletal displacement. The extreme speed of the mantis shrimp's raptorial appendage is due to the non-Euclidean hyperbolic paraboloid (i.e. saddle) shape within the dorsal region of the merus, which allows substantial energy storage through compression in the sagittal plane. Here, investigation of 3D printed synthetic geometries inspired by the mantis shrimp saddle geometry has revealed insights for elastic energy storage (i.e. spring-like) applications. Saddles composed of either astiffor aflexibleresin were investigated for spring response to explore the geometric effects. By modulating the saddle geometry and testing the spring response, it was found that, for thestiffresin, the spring constant was improved as the curvature of the contact and orthogonal faces were maximized and minimized, respectively. For theflexibleresin, it was found that the spring constant increased by less than 250 N mm-1as the saddle geometry changed, substantiating that the flexible component of mantis saddles does not contribute to energy storage capabilities. The geometries of two saddles from the mantis shrimp speciesO. scyllaruswere estimated and exhibited similar trends to manufactured saddles, suggesting that modulating saddle geometry can be used for tailored energy storage moduli in spatially constrained engineering applications.

Optical Properties and Mechanical Modeling of Acetylated Transparent Wood Composite Laminates.

Transparent wood composites (TWCs) are a new class of light-transmitting wood-based materials composed of a delignified wood template that is infiltrated with a refractive- index-matched polymer resin. Recent research has focused primarily on the fabrication and characterization of single-ply TWCs. However, multi-ply composite laminates are of interest due to the mechanical advantages they impart compared to the single ply. In this work, 1- and 2-ply [0°/90°] TWC laminates were fabricated using a delignified wood template (C) and an acetylated delignified wood template (AC). The optical and mechanical properties of resultant C and AC TWC laminates were determined using ultraviolet-visible spectroscopy (UV-Vis) and tensile testing (5× replicates), respectively. In addition, the ability of classical lamination plate theory and simple rule of mixtures to predict multi-ply tensile modulus and strength, respectively, from ply-level mechanical properties were investigated and are reported herein. Experimental results highlight tradeoffs that exist between the mechanical and optical responses of both unmodified and chemically modified TWCs. Template acetylation reduced the stiffness and strength in the 0° fiber direction by 2.4 GPa and 58.9 MPa, respectively, compared to the unmodified samples. At high wavelengths of light (>515 nm), AC samples exhibited higher transmittance than the C samples. Above 687 nm, the 2-ply AC sample exhibited a higher transmittance than the 1-ply C sample, indicating that thickness-dependent optical constraints can be overcome with improved interfacial interactions. Finally, both predictive models were successful in predicting the elastic modulus and tensile strength response for the 2-ply C and AC samples.