Fig. 2: Using tyr1 expressing K. rhaeticus to produce melanated BC.

a, The production process for melanated BC involves two steps. Tyrosinase-expressing K. rhaeticus are grown in static conditions to produce a pellicle. Once grown, this is collected and placed in development buffer and incubated with agitation between 30 °C and 50 °C until the material reaches the desired shade. b, Images show a time lapse of the progression of eumelanin accumulation over 24 h at 30 °C for K. rhaeticus ptyr1 and K. rhaeticus ctyr1 pellicles placed in development buffer. c, Pellicle production can be conducted in standardized containers to produce sheets of BC from which pattern pieces can be cut out and assembled. d, A K. rhaeticus ctyr1 pellicle, grown in a 300 × 200 mm container, after eumelanin development step. e, A finalized wallet prototype, cut and assembled from two pressed and dried melanated BC sheets. f, Pellicle production can also occur in shaped containers, producing BC preshaped to the 2D pattern of the final pattern piece. g, A K. rhaeticus ptyr1 pellicle grown in a shaped container, after eumelanin development. Metal pins seen within the perimeter of the pellicle hold a network of woven thread that becomes integrated into the pellicle during growth. h, A finalized shoe upper prototype produced from a melanated shaped BC sheet with integrated yarn that has been wrapped around a foot-shaped last and placed on a shoe sole.