Scalable bacterial production of moldable and recyclable biomineralized cellulose with tunable mechanical properties

Sustainable structural materials with excellent impact-resistance properties are urgently needed but challenging to produce, especially in a scalable fashion and with control over 3D shape. Here, we show that bacterial cellulose (BC) and bacterially precipitated calcium carbonate self-assemble into a layered structure reminiscent of tough biomineralized materials in nature (nacre, bone, dentin). The fabrication method consists of biomineralizing BC to form an organic/inorganic mixed slurry, in which calcium carbonate crystal size is controlled with bacterial poly(γ-glutamic acid) and magnesium ions. This slurry self-assembles into a layered material that combines high toughness and high impact and fire resistance. The rapid fabrication is readily scalable, without involving toxic chemicals. Notably, the biomineralized BC can be repeatedly recycled and molded into any desired 3D shape and size using a simple kitchen blender and sieve. This fully biodegradable composite is well suited for use as a component in daily life, including furniture, helmets, and protective garments.The authors thank Ward Groutars and Elvin Karana for useful discussions. K.Y. is supported financially by the China Scholarship Council (CSC no.201706630001). S.B. is funded by the Air Force Office of Scientific Research, Asian Office of Aerospace Research and Development (grant no. FA2386-18-1-4059)

Engineered Ureolytic Microorganisms Can Tailor the Morphology and Nanomechanical Properties of Microbial-Precipitated Calcium Carbonate

We demonstrate for the first time that the morphology and nanomechanical properties of calcium carbonate (CaCO ) can be tailored by modulating the precipitation kinetics of ureolytic microorganisms through genetic engineering. Many engineering applications employ microorganisms to produce CaCO . However, control over bacterial calcite morphology and material properties has not been demonstrated. We hypothesized that microorganisms genetically engineered for low urease activity would achieve larger calcite crystals with higher moduli. We compared precipitation kinetics, morphology, and nanomechanical properties for biogenic CaCO produced by two Escherichia coli (E. coli) strains that were engineered to display either high or low urease activity and the native producer Sporosarcina pasteurii. While all three microorganisms produced calcite, lower urease activity was associated with both slower initial calcium depletion rate and increased average calcite crystal size. Both calcite crystal size and nanoindentation moduli were also significantly higher for the low-urease activity E. coli compared with the high-urease activity E. coli. The relative resistance to inelastic deformation, measured via the ratio of nanoindentation hardness to modulus, was similar across microorganisms. These findings may enable design of novel advanced engineering materials where modulus is tailored to the application while resistance to irreversible deformation is not compromised.</p

Bone Tissue Material Properties Are Altered in Chronic Kidney Disease to Lower Fracture Resistance-Determining Bone Quality

Chronic kidney disease (CKD) is associated with a clinically-observed increase in bone fragility, yet the specific changes to fracture resistance-determining bone quality are not understood. CKD disrupts systemic mineral homeostasis and alters bone turnover. Thus, it was hypothesized that CKD deleteriously affects tissue-scale material properties. In Aim 1, mice with surgically-induced moderate CKD had diminished tissue-scale material properties, including mineral content and nanoindentation modulus, in bone formed during CKD compared with sham mice. Heterogeneity of microscale bone material was also altered with CKD. Next, CKD occurs most often in the elderly, yet geriatric patients with CKD have higher fracture risk than age-matched individuals without CKD. Aging reduces bone quality and may affect the behavior of osteocytes, the most prevalent type of bone cell. Osteocytes are essential for maintaining bone quality, but age-related changes to osteocytes, including lacunar morphologies, are not known. We hypothesized that osteocyte lacunae would have different morphologies with increasing age in mouse cortical bone. In Aim 2, we found that osteocytes become smaller, more spherical, and sparser with advancing age. Additionally, a convenient and inexpensive method to visualize and analyze 3D osteocyte lacunar geometries from confocal laser scanning microscopy depth stacks was presented. In Aim 3, it was hypothesized that aging and CKD together reduce bone material quality for mice with moderate CKD across the hierarchical organization of the bone tissue composite. We found that aging and CKD diminish bone material properties, including mineral and collagen matrix, from the microscale to the whole bone. Additionally, CKD reduced microscale material heterogeneity. Lastly, in Aim 4, it was hypothesized that fracture toughness depends on microscale material heterogeneity. In a rat model of exercise and obesity, fracture toughness of the femur was significantly influenced by the heterogeneity of nanoindentation modulus for lamellar bone. The relationship between fracture toughness and standard deviation of modulus had a negative quadratic form, implying that too-low or too-high variability in mechanical properties is deleterious to bone toughness. The collected work reported here provides insights into how bone material quality is diminished in CKD as well as how these changes may alter bone fracture resistance

INVESTIGATION OF ADSORBENT BEHAVIOR BY GAS-SOLID CHROMATOGRAPHY

Abstract not availabl

Carpenter bee thorax vibration and force generation inform pollen release mechanisms during floral buzzing

Approximately 10% of flowering plant species conceal their pollen within tube-like poricidal anthers. Bees extract pollen from poricidal anthers via floral buzzing, a behavior during which they apply cyclic forces by biting the anther and rapidly contracting their flight muscles. The success of pollen extraction during floral buzzing relies on the direction and magnitude of the forces applied by the bees, yet these forces and forcing directions have not been previously quantified. In this work, we developed an experiment to simultaneously measure the directional forces and thorax kinematics produced by carpenter bees (Xylocopa californica) during defensive buzzing, a behavior regulated by similar physiological mechanisms as floral buzzing. We found that the buzzing frequencies averaged about 130 Hz and were highly variable within individuals. Force amplitudes were on average 170 mN, but at times reached nearly 500 mN. These forces were 30–80 times greater than the weight of the bees tested. The two largest forces occurred within a plane formed by the bees’ flight muscles. Force amplitudes were moderately correlated with thorax displacement, velocity and acceleration amplitudes but only weakly correlated with buzzing frequency. Linear models developed through this work provide a mechanism to estimate forces produced during non-flight behaviors based on thorax kinematic measurements in carpenter bees. Based on the buzzing frequencies, individual bee’s capacity to vary buzz frequency and predominant forcing directions, we hypothesize that carpenter bees leverage vibration amplification to increase the deformation of poricidal anthers, and hence the amount of pollen ejected. © 2022, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The impacts of biomineralization and oil contamination on the compressive strength of waste plastic-filled mortar.

Researchers have made headway against challenges of increasing cement infrastructure and low plastic recycling rates by using waste plastic in cementitious materials. Past studies indicate that microbially induced calcium carbonate precipitation (MICP) to coat plastic in calcium carbonate may improve the strength. The objective of this study was to increase the amount of clean and contaminated waste plastic that can be added to mortar and to assess whether MICP treatment enhances the strength. The performance of plastic-filled mortar was investigated at 5%, 10%, and 20% volume replacement for cement. Untreated, clean plastics at a 20% cement replacement produced compressive strengths acceptable for several applications. However, a coating of MICP on clean waste plastic did not improve the strengths. At 10% replacement, both MICP treatment and washing of contaminated plastics recovered compressive strengths by approximately 28%, relative to mortar containing oil-coated plastics. By incorporating greater volumes of waste plastics into mortar, the sustainability of cementitious composites has the potential of being improved by the dual mechanisms of reduced cement production and repurposing plastic waste