Prodigiosin is a microbial red pigment, mainly produced by the bacterium Serratia marcescens, considered as a promising antimicrobial, immunosuppressive and antiproliferative compound. However, its industrial commercialization is still limited because of the high cost of production mainly due to the use of expensive substrates. Hence, this work aimed to the sustainable production of prodigiosin by S. marcescens UCP 1549, using corn bran as alternative and low-cost substrate, and its application in soap coloring. According to the results, both bacterial growth and red pigment production occurred, achieving 7.24 g/L and 1.68 g/L of biomass and pigment yield, respectively. Positive result in the presumptive test indicated red pigment as prodigiosin, which was confirmed by UV-Visible spectrophotometry (maximum absorbance peak at 535 nm), TLC (Rf 0.9) and the functional groups identified by FTIR spectroscopy. Prodigiosin showed color stability at different pH values and NaCl concentration. The application of pigment in soap coloring was effective, suggesting its promising potential in the cosmetics industry as natural colorant. The results showed the biotechnological potential of S. marcescens UCP 1549 in the biotransformation of corn bran into prodigiosin, allowing a more economically and competitively industrial bioprocess.

Biomolecules of microbial origin are gaining attention for their use in various industries, including cosmetics, due to their broad bioactivities, peculiar properties, and sustainability. This study aimed to develop a novel, eco-friendly nanoemulsion from fungal chitosan hydrochloride (ChC), Pseudomonas aeruginosa biosurfactant (PaB), and grape seed oil (GSO), and to assess its antimicrobial action, biofilm control, and biocompatibility. High-energy emulsification was performed to produce the nanoemulsion (CCh-PaB-GSO), which was characterized by FTIR. Its stability was monitored for 30 days via DLS, zeta potential (ZP), and PDI. The minimum inhibitory concentration (MIC) for cariogenic Streptococcus species, inhibitory fraction concentration (FIC), influence on exopolysaccharide (EPS) quantification produced by bacteria, bacteria’s cell wall hydrophobicity, and biofilm control were determined. Biocompatibility was assessed using the HET-CAM technique by determining the irritation potential. FTIR analysis confirmed the formation the interaction between the substances that compound the nanoemulsion. The CCh-PaB-GSO had nanometric micelles (169.5–203.4 nm), PDI (0.241–0.271), and a positive ZP (+20.25 to +31.94 mV). It showed a consistent MIC (2.0 mg/mL CCh, 0.1 mg/mL PaB, and 3.2 mg/mL GSO) for all tested Streptococcus species and an indifferent interaction effect, FIC (1.32). At sub-MIC, the CCh-PaB-GSO effectively reduced EPS and microbial cell wall hydrophobicity, inhibiting biofilm adhesion. The CCh-PaB-GSO demonstrated biocompatibility with no signs of irritation. In conclusion, the ChC-PaB-GSO system forms an effective and stable nanoemulsion with potential for application as an eco-sustainable and biocompatible product for caries control.