One-Pot Production of Melanised Bacterial Cellulose through Rational Enzyme Engineering

Textiles and fashion industries face increased pressure to reduce their environmental footprint, as conventional dyeing and synthetic leather production consuming a large amount of water, resources, and energy as well as generating persistent pollutants. Bacterial cellulose (BC) offers a sustainable alternative due to its high purity, biodegradability, and mechanical strength. However, integrating pigmentation during BC biosynthesis has been hindered by incompatibilities between melanin production and the acidic conditions required for efficient BC formation.

In this study, we present a one-pot, one-step co-culture strategy combining Komagataeibacter xylinus with engineered Escherichia coli expressing an acid-tolerant tyrosinase variant (TyrMut_Pm) designed through rational in silico mutagenesis. TyrMut_Pm exhibited a 2.07-fold higher initial activity at pH 5 compared to the wild-type enzyme (1.284 × 10⁻² versus 6.209 × 10⁻³ ΔA₄₀₅/min), directly enabling melanin biosynthesis under the acidic conditions of BC fermentation and eliminating the need for secondary development baths, while maintaining efficient cellulose production and reducing process complexity. The resulting melanised BC exhibits leather-like properties after glycerol-assisted leatherisation, with tensile strength and flexibility comparable to synthetic vegan leathers, alongside excellent colour fastness and full biodegradability under composting conditions. Through the rational design of an acid-tolerant tyrosinase integrated into a one-pot co-culture, this study establishes a rigorously validated biomanufacturing platform that synchronises melanin biosynthesis with bacterial cellulose assembly. By eliminating conventional multi-stage dyeing and minimising water, energy, and chemical inputs, this approach delivers a scalable, fully characterised bio-composite that advances the cleaner materials paradigm through a circular, low-impact alternative to petrochemical synthetic leathers.