This research explores the sustainable production and application of biodegradable films enhanced with microbial melanin, offering a promising alternative to synthetic packaging materials. Agricultural waste streams—cheese whey and citrus waste—were valorized for the biotechnological production of single cell protein (SCP), bacterial cellulose (BC), and microbial melanin (MM). SCP refers to dry cells of microorganisms rich in protein, while BC is a biopolymer which presents an excellent candidate for the development of sustainable materials due to its physicochemical characteristics. MM is a biopolymer with high environmental interest, derived from “black yeasts”. SCP and BC were produced using Kluyveromyces marxianus EXF-5288 and Komagataeibacter rhaeticus UNIWA AAK2, respectively, while Exophiala phaeomuriformis EXF-6108 was used to produce melanin from citrus waste. Two melanin extraction methods were evaluated: autoclave-based and ultrasound-assisted.

Although the autoclave method led to higher yields of pigment, the ultrasound method preserved melanin’s functional properties more effectively and proved more sustainable. The incorporation of melanin into SCP- and BC-based films improved UV-blocking capacity, particularly in the UVC and UVB ranges, and altered other properties including color, solubility, and mechanical strength. Glucose was found to be the most effective carbon source for BC production compare to lactose obtained from cheese whey. SCP films with 20% melanin showed complete UVC/UVB blockage and improved opacity, however mechanical analysis showed poor results for tensile strength. These findings support the development of functional, biobased packaging materials aligned with circular economy principles.

Eirini Tolia, Freideriki Gala, Danai Ioanna Koukoumaki, Katerina Petridi, Dimitris Sarris; Laboratory of Physico-Chemical and Biotechnological Valorization of Food By-Products Department of Food Science and Nutrition, School of the Environment, University of the Aegean.