Engineering Biocatalytic And Living Materials

Abstract

Providing clean and safe water to the world’s growing human population in one of the major challenges of the 21st century. Increased human activity contaminates waters with toxic chemicals, making it unsafe for consumption. Bioremediation utilizing encapsulated bacteria has emerged as an efficient method for the removal of toxic chemicals from the environment, and can permanently remove a wide range of pollutants by breaking them down into simple compounds. In this presentation, biocatalytic materials were developed for water bioremediation utilizing encapsulated bacteria. Silica gels with encapsulated bacterial cells and spores were designed and optimized for cytocompatibility, porosity, and catalytic activity. As a case study, the gels were used to remove a hydrophobic herbicide from drinking water. First, the surface properties or the silica gel were optimized for biodegradation of the hydrophobic herbicide, by incorporating hydrophobic side chains into the gel. The hydrophobic groups rapidly removed the herbicide by adsorption, and the adsorbed herbicide was rapidly degraded by encapsulated cells, resulting in high biodegradation rates. Next, materials were engineered for the encapsulation, germination and outgrowth of bacterial spores. Encapsulation of the robust bacterial spores enabled a much wider range of synesis conditions, resulting in materials with better mechanical properties. After encapsulation, spores could be germinated by adding nutrients, causing them to grow into metabolically active cells. In addition, spores could be encapsulated in desiccated materials, enabling long term storage with a low risk of fowling. After the gels were designed and characterized, an emulsion system was developed for production of silica gel microspheres with encapsulated bacteria for use in a packed bed bioreactor, and the system was scaled up to produce 52 gallons of microspheres for field test. Finally, robust bionanocomposites with controlled morphologies were produced via the self-assembly and biosilification of fusion proteins. The scaffold forming protein EutM was genetically fused to four different silica biomineralization peptides, enabling control over the scaffold morphology and extent of biosilicification. At high silica concentrations, the proteins catalyzed the formation of a macroscale silica gel, and the microstructure and mechanical properties of the gel could be tuned by adjusted the protein concentration. The silica precipitating protein scaffolds developed in this work represent an ideal biomaterial for the fabrication of living materials because of their small size, self-assembling properties and their robustness.