Otto Kevin Pereira da Silva

Demand for natural red colorants has increased due to regulatory and consumer pressure to replace synthetic additives; however, their industrial application remains limited by challenges related to production, stability, and safety. In this study, the production, physicochemical stability, antimicrobial activity, and preliminary cytotoxicity of an azaphilone-type red colorant produced by Talaromyces sp. C1I3 under submerged fermentation were evaluated. Two sequential Box–Behnken designs identified optimal production conditions at approximately pH 5.8, 60 rpm, and 15.15 g·L⁻¹ monosodium glutamate. Under these conditions, colorant production increased from 1.46 AU_500nm on day 5 to 9.9 AU_500nm on day 10, with estimated kinetic parameters of µmax 0.0109 h⁻¹ and Yx/s 0.63 g·g⁻¹. The colorant showed high thermal stability, retaining approximately 95% of its color after heating at 80 °C for 10 min, and remained stable over a broad pH range, with only 18% degradation after 168 h of light exposure. No significant antimicrobial activity was detected, indicating that the colorant primarily functions as a color additive without additional bioactive effects. Furthermore, no acute cytotoxicity was observed in human neonatal dermal fibroblasts at concentrations ranging from 0.5 to 15 µg·mL⁻¹. These findings demonstrate the potential of this fungal colorant as a stable and safe natural colorant for future industrial applications.

Chitosan/collagen hydrogels have gained prominence in biomedical applications due to their biocompatibility and ability to promote tissue regeneration. However, rheological instability may limit their applicability. This study investigated the structural and rheological properties of chitosan/collagen hydrogels (99:1, 97:3, and 95:5%) crosslinked with 0.1% genipin. The samples were characterized by Fourier Transform Infrared Spectroscopy (FTIR), injectability, viscosity, swelling, biodegradation, and blood clotting time. Genipin crosslinking improved structural stability, increased viscosity and extrusion resistance, and provided slower and more predictable mass loss under physiological and enzymatic conditions. The swelling assay showed a progressive reduction in water uptake with increasing collagen content, further accentuated by genipin, suggesting a denser and more stable polymeric network. Additionally, the hydrogels accelerated blood coagulation, reinforcing their potential use as hemostatic agents.