SynBio, Volume 4, Issue 2 (June 2026) – 3 articles

Solitary bees account for most described bee species worldwide, with many spinning silk fibers to form protective cocoons during development; however, solitary bee silk proteins remain largely unexplored in recombinant systems and biomaterial fabrication. Here, we report the first recombinant expression and biomaterial formation from a solitary bee silk protein. Osmia lignaria silk fibroin 2 (OligF2) was expressed in Escherichia coli BL21(DE3) using an expression and purification scheme adapted from a recombinant hagfish intermediate filament (rHIF) workflow, yielding 0.34 g/L at ~70% purity. The purified OligF2 protein was cast into films at 0.75% and 1% (w/v). Fourier-transform infrared attenuated total reflectance (FTIR-ATR) analysis estimated higher β-sheet content in 0.75% films (50.3%) than in 1% films (42.3%). Mechanical testing yielded elastic moduli of 7.83 ± 2.73 MPa and 6.80 ± 1.89 MPa for the 0.75% and 1% films, respectively. These results establish the first recombinant production and biomaterial formation of a solitary bee silk protein, providing a foundation for exploring this class of recombinant proteins for the development of tunable biomaterials. Full article

Indole-3-acetic acid (IAA) is the main natural auxin and a key regulator of plant growth. However, most commercial auxins are synthetically produced from non-renewable resources. Here, we present a minimal synthetic biology platform for microbial IAA production that also serves as a teaching model for genetic circuit design and bioprocess development. We developed codon-optimized versions of the iaaM and iaaH genes, which encode tryptophan 2-monooxygenase and indole-3-acetamide hydrolase, and assembled them into a compact expression cassette in Escherichia coli TOP10. Correct expression of both enzymes was confirmed by SDS-PAGE. The engineered strain was cultivated in a low-cost medium made from avocado seed hydrolysate, an agro-industrial waste, supplemented with tryptophan as a precursor. IAA was quantified using the Salkowski colorimetric assay and further validated by HPLC, reaching approximately 303–313 µg/mL at 48 h, with the medium costing approximately fivefold cheaper locally than traditional LB. The supernatants containing biosynthetic IAA induced root formation in 100% of tobacco leaf explants, outperforming the commercial standard at the same concentration and confirming biological activity. Since this workflow follows the Design–Build–Test–Learn (DBTL) cycle, Design (pathway selection and codon optimization), Build (plasmid assembly), Test (protein expression, metabolite quantification, plant bioassays), and Learn (medium and process optimization), it provides a sustainable production method and an accessible educational platform for synthetic biology. Full article

Lipid nanodiscs are synthetic nanoparticles capable of solubilizing lipophilic drugs and have been shown to improve the potency of the antifungal Amphotericin B (AmphB) against various fungal pathogens. In this study, the SpyCatcher–SpyTag covalent labeling system was used to couple AmphB-loaded Apolipoprotein A1 (ApoA1) lipid nanodiscs to the receptor domain of Dectin-1, which binds to β-1,3/1,6 glucans present in many fungal cell walls. Denaturing protein gel electrophoresis demonstrated that ApoA1-SpyTag003 lipid nanodiscs could be covalently labeled with SpyCatcher003-Dectin-1-superfolder GFP (sfGFP). In microtiter growth assays with Saccharomyces cerevisiae, Dectin-1 AmphB nanodiscs displayed an IC₅₀ 1.5-fold lower than uncoupled AmphB nanodiscs and 2.8-fold lower than AmphB-only controls. Nanodiscs without AmphB and SpyCatcher003-Dectin-1-sfGFP themselves did not inhibit yeast growth. Fluorescence microscopy showed that SpyCatcher003-Dectin-1-sfGFP binds to yeast cell walls and accumulated at hot spots, matching the budding scar enrichment pattern previously described for other Dectin-1 fusion proteins. Together these results indicate that Dectin-1 fusions can target AmphB-loaded lipid nanodiscs to fungal cell walls and improve drug delivery. The results here establish the use of a modular SpyCatcher–SpyTag coupling system for targeting drug-loaded lipid nanodiscs to different cells or tissues, thereby increasing drug retention at infection sites, increasing drug potency, and reducing harmful side-effects. Full article