Naturally coloured poly(3‐hydroxybutyrate)

Abstract

This study reports an innovative approach for producing intrinsically coloured poly(3‐hydroxybutyrate) [P(3HB)] films by incorporating natural dyes—turmeric, paprika, annatto, beetroot and hibiscus—directly into the fermentation medium of Ralstonia solanacearum RS. The process eliminates the need for post‐synthesis coloration or genetic modification, offering a streamlined and sustainable method. The films were evaluated for colour stability under photodegradation, saline exposure and oil immersion, alongside morphological, wettability and thermal characterisations. Carotenoid‐based dyes (turmeric, paprika and annatto) successfully imparted colour to the films, with paprika and annatto showing superior stability to light, saline and oil conditions compared to turmeric. Scanning Electron Microscopy revealed reduced porosity in dyed films, especially with annatto, suggesting dye‐induced morphological protection. The incorporation of natural dyes significantly increased the films' hydrophilicity without compromising thermal stability, although slight variations in crystallinity were observed. These findings demonstrate the potential of naturally coloured P(3HB) films for sustainable applications such as smart and biodegradable packaging, while paving the way for further research on industrial scalability and long‐term performance.