ChromoBC: Designing colour and responsiveness in bacterial cellulose

Abstract

Colour is usually added to materials after fabrication. ChromoBC presents a different approach using bacterial cellulose (BC) that has exceptional mechanical properties and can be microbially produced from low-cost carbon sources. ChromoBC encodes colour and responsiveness into a material that is grown by microbes and whose properties can be genetically programmed. In this work, we demonstrate four colouring modes. In the first approach, the cellulose-producing bacterium, Komagataeibacter rhaeticus , expresses visible proteins that paint the growing cellulose. In the second, K. rhaeticus synthesises eumelanin via an engineered biopathway that forms tuneable grey-to-black materials. As a responsive material, anthocyanin-loaded BC reports environmental pH through instant colour changes. The fourth mode uses a synthetic symbiotic co-culture of bacteria and yeast (Syn-SCOBY) to develop a living, responsive cellulose-based material. The engineered baker’s yeast, Saccharomyces cerevisiae , functionalises cellulose with a secreted enzyme, allowing a chemical input to trigger a colour change. Together, these prototypes demonstrate different forms of BC-based colour-changing materials that can be permanent, tuneable, reversible and responsive. At BioDesign 2026, visitors encountered ChromoBC as a hands-on BC-based material palette, testing pH-responsive material and activating enzyme-based colour changes. This demo positions biologically designed BC as a sustainable and tuneable interface in which biological processes become visible and interactive.