From extreme environments to skin interfaces: thermophilic exopolysaccharides as smart and sustainable polymers for advanced cosmeceutical and transdermal applications.

Microbial exopolysaccharides (EPS) possess strong potential for next-generation biomaterials due to their sustainability, biodegradability, and biocompatibility as the promising replacements for fossil-derived polymers. Conventional synthetic and semi-synthetic polymers have been used for pharmaceutical and cosmetic applications but due to their limitations-particularly in advanced skin-interface technologies-the need for safe and environmentally friendly alternatives has emerged. Thermophilic microorganisms, which have high growth activity in extreme conditions and synthesize extracellular polymeric substances (EPS) as materials that are functionally acting as protective matrix structures outside the cell, seem to be the most promising natural solution. The latter type of EPS has unique physicochemical characteristics, such as thermal stability and viscosity, in addition to certain functional groups. Such properties enable their use in complex applications (e.g. hydrogels, nanoparticles, and hybrid delivery systems), where they benefit on drug stability, skin permeation, and unwanted effects. Regarding composition, EPS are polysaccharides comprising repeating monosaccharide units linked by glycosidic bonds. These polymers possess valuable intrinsic properties that make them highly attractive for pharmaceutical, cosmetic and food industries such as biodegradability, non-toxicity and tunable properties. In contrast to plant-derived polysaccharides, microbial EPS accumulate in a highly controlled manner with predictable and reproducible qualities that lend themselves to large-scale biotechnological production. Current limitations like production cost and downstream processing will likely be overcome by future advances in biotransformation biotechnology and process optimization. Translating the need for EPS-based materials into commercially viable and sustainable solutions of future application will require great cooperation among researchers, industry and regulatory bodies.