The Nano3Bio project convenes a consortium of world renowned experts from 8 EU universities, 1 large company, and 14 SME, to develop biotechnological production systems for nanoformulated chitosans. Chitosans, chitin-derived polysaccharides varying in their degree of polymerisation (DP), degree of acetylation (DA), and pattern of acetylation (PA), are among the most versatile and most promising biopolymers, with excellent physico-chemical and material properties, and a wide range of biological functionalities, but their economic potential is far from being exploited due to i) problems with reproducibility of biological activities as today’s chitosans are rather poorly defined mixtures, and ii) the threat of allergen contamination from their typical animal origin. The Nano3Bio project will overcome these hurdles to market entry and penetration by producing in vitro and in vivo defined oligo- and polymers with controlled, tailor-made DP, DA, and PA. Genes for chitin synthases, chitin deacetylases, and transglycosylating chitinases/chitosanases will be mined from different (meta)genomic sources and heterologously expressed, the recombinant enzymes characterized and optimized by protein engineering through rational design and molecular evolution, e.g. targeting engineered glycosynthases. These enzymes and genes will be used for in vitro and in vivo biosynthesis in microbial and microalgal systems, focusing on bacteria and diatoms. The bioinspired chitosans will be formulated into biomineralised hydrogels, nanoparticles, nanoscaffolds, etc., to impart novel properties, including by surface nano-imprinting, and will be bench-marked against their conventional counterparts in a variety of cell based assays and routine industrial tests for e.g. cosmetics and pharma markets. The process will be accompanied by comprehensive life cycle assessments including thorough legal landscaping, and by dissemination activities targeted to the scientific community and the general public.