Dyeing wet blue goat nappa skin with a microbial colorant obtained from Penicillium minioluteum

• Eco-friendly dye able red color was obtained from a fungi Penicillium minioluteum.
• The colorant was identified as acid dye by chemical and spectroscopic methods.
• Wet blue goat nappa skin was best dyed at pH 2.0 at 80 °C for 60 min.
• Presence of organic compounds led to faster absorption and enhanced shade.
• Dyed samples showed good rub fastness with unchanged tear and tensile strength.

A colorant from Penicillium minioluteum behaving like an acid dye was identified, extracted, purified, and characterized. It was used for dyeing wet blue goat nappa skin at different pH, time, and temperature to standardize these parameters. Highest color depth and percentage dye exhaustion was achieved at pH 2.0 (altered after 30 min of dyeing), temperature 80 °C, and time 60 min. Study of dyeing mechanism revealed adsorption phenomenon similar to the Langmuir distribution. Interestingly, color diffusion was found to be uniform, faster, and attained equilibrium in a shorter span of time unlike conventional leather dyeing process. It was due to the presence of proteases; organic polyphenols; functional amphoteric auxiliaries; and alcohols and amines as per Fourier transform infrared spectroscopy in the colorant. Final sample dyed using standardized dyeing conditions showed good rub fastness and marked to moderate perspiration fastness. However, light fastness was found to be very poor. Furthermore, no change in tear and tensile strength was recorded in the dyed samples as compared to the undyed sample.