Production, biological characterization, and applications of natural pigments from filamentous fungi

Natural dyes are gaining prominence as safer, bioactive alternatives to synthetic colorants, with microbial production offering efficient and cost-effective methods. This study isolated and evaluated pigment-producing fungi from Saudi Arabia's Eastern Province, identifying Sabouraud Dextrose Agar (SDA) as optimal for initial screening. While ten high-yield strains were tested in liquid fermentation and immobilization, solid-state fermentation yielded superior pigment production. Genetic sequencing identified the top five strains as Aspergillus terreus (PQ134479), Fusarium solani (PQ134082), Achaetomium cristalliferum (PQ134101), Chaetomium strumarium (PQ134105) and Aspergillus terreus (PQ133589), Water proved to be the best extraction solvent. Optimization of culture conditions revealed temperature and pH as critical factors for pigment yield. Antimicrobial assays showed promising inhibitory effects against two multidrug resistance strains which are Staphylococcus aureus MRSA (PQ097594) and Escherichia coli ESBL (PQ097597), ABTS assays indicated strong, dose-dependent antioxidant activity, particularly for C. strumarium. Acute toxicity tests on Daphnia magna confirmed the pigments' non-toxic nature. Successful textile dyeing on cotton and wool was achieved, with alum showing the best color fixation. Food applications in rice and dough demonstrated good thermal stability and color retention. These findings underscore the potential of fungal pigments as sustainable, non-toxic alternatives for industrial applications, particularly in the food and textile sectors.