Investigation of the optimal production conditions of some bacterial and fungal pigments and their antimicrobial properties

Colorants are widely used today in many fields such as food, textile, cosmetics, and toy industries. It is highly important that these colorants are natural rather than synthetic and do not pose harmful effects on human health. Therefore, there is an increasing demand for alternative pigment sources that can be produced easily and in large quantities, are independent of climatic conditions, cost-effective, and safer for human use. Microbial pigments, which possess these advantages, have attracted considerable attention for use in various industries. In this study, it was aimed to optimize the production conditions of certain pigment-producing bacteria and fungi. For this purpose, the optimum pigment production conditions of the fungus Fusarium oxysporum and the bacterium Serratia marcescens were investigated. As alternative production media, Sabouraud Dextrose Agar (SDA), Potato Dextrose Agar (PDA), and Czapek Agar were used for F. oxysporum, while Nutrient Agar (NA) and Luria–Bertani Agar (LB) were used for S. marcescens. Different production parameters, such as incubation time, temperature, initial pH, and agitation conditions, were tested to increase microbial pigment production. Subsequently, the bacterial and fungal pigments obtained under optimum conditions were extracted using appropriate solvents and partially purified. Their characterization was performed by UV–Vis spectrophotometry, FT-IR, NMR, and GC-MS analyses, and their antimicrobial properties were also determined. As a result, PDA was determined to be the most suitable medium for pigment production by F. oxysporum. Maximum pigment production was achieved under light incubation conditions, at 150 rpm shaking speed, 25 ºC temperature, initial pH 9.0, and 7 days of incubation. For S. marcescens, Luria–Bertani (LB) medium was found to be the most suitable medium for pigment production. Optimum pigment production was obtained static cultivation, 20 ºC temperature, initial pH 5.0, and 4 days of incubation.