Photosynthetic microorganisms, such as microalgae and cyanobacteria, have immense potential for fossil-free production of desired compounds and can play a crucial role in sustainable biotechnologies. In contrast to conventional biorefinery approaches applied to microalgal biomass, biocatalytic production with engineered photosynthetic microbes involves the production of targeted chemicals using light energy, which are then secreted, enabling a "milking" process. We explore two distinct approaches to biocatalytic production. In the first approach, photosynthetic cells serve as whole-cell catalysts, converting introduced chemicals (e.g. cyclohexanone) into desired products (e.g. ε-caprolactone) by utilizing photosynthetically produced molecular oxygen and reducing equivivalents such as NADPH. This approach allows for sustainable cofactor regeneration through photosynthesis, overcoming a major challenge in biocatalytic production.
In the second approach, we transform suspension cultures into photosynthetic engineered living materials (hydrogels) by encapsulating cells within an environmentally friendly polymeric scaffold matrix. This method ensures a safe and controlled environment for the cells, addressing various challenges associated with suspension cultures and enabling long-term production (several months). In case studies, 3D-printed cyanobacterial and microalgal cells, entrapped within thin hydrogel layers using photocurable polymers, exhibited notably high production titers and space–time yields compared to conventional biocatalysts. These photosynthetic engineered living materials, which are biocompatible and derived from renewable resources, particularly when integrated with 3D printing, offer scalability and the potential to enhance sustainability in the chemical industry.