Bright Thermo-resilient and Promiscuous Zombie Protein for Lighting Applications

Proteins are at the forefront of materials science, with implementations in optical, electrical, and structural materials for transformative and sustainable technologies. Within the biohybrid light-emitting diode (BioHLED) concept, replacing toxic and/or rare photon filters with classical β-barrel fluorescent proteins (FPs) that must withstand irradiation, temperature, oxidation, and dehydration stress, the question if FPs from extremophiles and/or living fossils might be better for lighting applications arises. We addressed this by introducing a thermostable prokaryotic FP, whose inherent promiscuity enables the design of tunable emitting proteins. Three milestones were reached: (i) a comprehensive phylogeny of phycobiliproteins from a large data set (182 proteins from 29 thermophiles) to identify the most versatile zombie-like phycobiliprotein (highly ancestral character), (ii) heterologous expression of this phycobiliprotein (SPritZ) in Escherichia coli and further enhancement via rational mutagenesis into a brighter and more thermal-resilient variant (eSPritZ), and (iii) 2.5-fold stable BioHLEDs comparing SPritZ vs eSPritZ in hydroxypropyl cellulose coatings.