The continued spread of anti-microbial resistant bacterial pathogens together with a lag in the development of suitable antibiotic alternatives set the alarm bells ringing in public and animal health. In this project proposal, ImmunoKeys, synthetic biology and animal immunology experts join forces to engineer microbial cell factories capable of producing structurally well-defined (partially acetylated) chitooligosaccharides with optimal immunostimulating properties via an integrated Design-Build-Test-Learn (DBTL) cycle. The obtained knowledge will lay the foundation for the development of these glycans as innovative alternatives for antibiotics in animal health.