Isolation and Characterization of a Novel Crystalline Pigment as a Natural Colorant

Abstract

This research focuses on the isolation and thorough characterization of a distinctive pigment-producing bacterial strain, ACFM05, obtained from Daucus carota subsp. Sativus (Carrots). The pigment was systematically examined for morphological, microscopic, biochemical, and molecular features, utilizing 16S rRNA sequencing. The strain was identified as a novel species within the Micrococcus genus, specifically classified as Micrococcus yunnanensis. The optimization of pigment extraction parameters revealed a pH of 8 at 40 °C as the ideal conditions for maximum yield. UV studies indicated that the pigment, extracted with methanol as the solvent, exhibited a notable absorption peak at 445 nm, closely resembling the absorption peak of carotenoids. The growth biomass of the bacteria was found to be influenced by the antioxidant activity, reducing power assay, and total phenolic content. The pigment extracts were further evaluated for their antifungal, antibiotic sensitivity, and antibacterial activities against Pseudomonas, Staphylococcus aureus, and Escherichia coli. Results indicated significant potential for the pigment as an antimicrobial agent. To elucidate the molecular and structural characteristics of the pigment, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA), and scanning electron microscopy (SEM) analyses were employed. The findings from these analyses collectively confirmed the presence of carotenoids in the bacterial pigment. Furthermore, XRD studies revealed the crystalline nature of the pigment. In conclusion, the unique crystalline pigment isolated from Micrococcus yunnanensis ACFM05 demonstrates promising potential as a natural colorant for food applications. This study contributes valuable insights into the microbial production of pigments with multifaceted applications in the food industry.