Aksan, A. | bioRxiv Science

bioRxiv2021

Engineering Bacillus subtilis for the formation of a durable living biocomposite material

Engineered living materials (ELMs) are a fast-growing area of research that combine approaches in synthetic biology and material science. Here, we engineer B. subtilis to become a living component of a silica material composed of self-assembling protein scaffolds for functionalization and cross-linking of cells. B. subtilis was engineered to display SpyTags on polar flagella for cell attachment and cross-linking of SpyCatcher modified secreted scaffolds. Through deletion of the autolysis LytC, endospore limited B. subtilis cells become a structural component of the material with spores for long-term storage of genetic programming. Known silica biomineralization peptides were screened and scaffolds designed for silica polymerization to fabricate biocomposite materials with enhanced mechanical properties. We show that the resulting ELM can be regenerated from a piece of silica material and that new functions can be readily incorporated by co-cultivation of engineered B. subtilis strains. We believe that this work will serve as a framework for the future design of resilient ELMs as functional, self-healing materials for use as responsive coatings and plasters.

synthetic biology↗

bioRxiv2018

Dextranol: A better lyoprotectant

Dextranol, a reduced dextran, prevents damage to stored dry protein samples that unmodified dextran would otherwise cause. Lyoprotectants like the polysaccharide dextran are critical for preserving dried protein samples by forming rigid a glass that protects entrapped protein molecules. Stably dried proteins are important for maintaining critical information in clinical samples like blood serum. However, we found that dextran reacts with serum proteins during storage, producing high-molecular weight Amadori-product conjugates. These conjugates appeared in a matter of days or weeks when stored at elevated temperatures (37{degrees} or 45{degrees}C), but also appeared on a timescale of months when stored at room temperature. We synthesized a less reactive dextranol by reducing dextrans anomeric carbon from an aldehyde to an alcohol. Serum samples dried in a dextranol- based matrix protected the serum proteins from forming high-molecular weight conjugates. The levels of four cancer-related serum biomarkers (prostate specific antigen, neuropilin-1, osteopontin, and metalloproteinase 7) decreased, as measured by immunoassay, when serum samples were stored for one to two weeks in dextran- based matrix. Switching to a dextran-based lyoprotection matrix slightly reduced the damage to osteopontin and completely stopped any detectable damage during storage in the other three biomarkers when for a period of two weeks at 45{degrees}C. Dextranol offers a small and easy modification to dextran that significantly improves the molecules function as a lyoprotectant by eliminating the potential for damaging protein-polysacharide conjugation.

biochemistry↗