Production of red pigment from salinicoccus sp. and its functional properties in food

Abstract

With the growing global demand for natural colorants to replace synthetic dyes, functional microbial pigments have emerged as highly promising candidates for commercial development. This study investigated the genetic properties of Salinicoccus sp. strain 82-1, a halophilic bacterium isolated from pla-ra (Thai fermented fish). This research studies its growth and pink-red pigment production characteristics, evaluated pigment extraction and stabilization methods, and assessed its functional properties in food model systems. Whole-genome sequencing (WGS) and phylogenomic analysis identified the microbial strain as Salinicoccus cyprini, exhibiting genetic similarities, 86.30% for digital DNA-DNA hybridization (dDDH), and Average Nucleotide Identities of 97.90% (ANIb) and 98.52% (ANIm) with the type strain S. cyprini CT19. Genomic annotation predicted 2,620 protein-coding genes and revealed gene clusters associated with pigment biosynthesis, particularly for carotenoids. Cultivation of Salinicoccus sp. 82-1 in a 5-liter bioreactor (3,300 mL working volume) demonstrated maximum cell growth at 12 hours and peak pigment production at 72 hours, yielding a wet cell mass of 8.46 g/L. Evaluation of pigment extraction efficacy using chemical (solvent), biological (lysozyme), and physical (ultrasonic) methods revealed that ultrasonic extraction yielded the highest absorbance (0.610, 0.560, and 0.490 at wavelengths of 489, 509, and 541 nm, respectively). Following the optimization of ultrasonic extraction conditions, pigment extraction using ultrasonication for 15 minutes yields the best extraction. The pigment was stabilized into a powder form using hot-air oven with maltodextrin as a carrier at 5%, 10%, and 15% (w/v), compared to carrier-free sample. Visual color characteristics across all samples, before and after drying, showed no significant differences (p > 0.01). However, the carrier-free pigment powder exhibited significantly higher antioxidant activity (p<0.01), with a DPPH radical scavenging activity of 21.2 = 0.6% and a FRAP value of 446.13 = 3.46 uM Trolox Equivalent. Therefore, the carrier-free powder was selected for application in food models to compare its efficacy against synthetic colorants. In (i) yogurt, the natural pigment powder did not affect the fermentation process and demonstrated superior color stability compared to the synthetic dye. In (i) cream, the pigment powder significantly slowed the increase in peroxide value (p ‹ 0.01); on day 15 of storage, the cream with synthetic dye reached a peroxide value of 4.67 = 0.58 mea/kg, whereas the cream with natural pigment powder remained lower at 1.67 = 0.58 meg/kg. These findings indicate that Salinicoccus sp. 82-1 holds substantial potential as a functional natural pigment source for application as a natural food additive.