Physico-chemical factors and nanomaterial-mediated optimization of pigment yield from a psychrotrophic marine Citricoccus-like isolate of an Arctic fjord

Abstract

Bacterial pigments have broad industrial applications and are relatively easy to scale up. However, Arctic microbial sources remain largely unexplored. In this study, we isolated a yellow-pigmented bacterium, PS104, from the Arctic Ny-Ålesund fjord in Kongsfjorden, Svalbard, Norway. Biochemical assays and 16S rRNA gene sequencing revealed that PS104 is closely related to the genus Citricoccus. Pigment characterization using UV–visible spectroscopy showed a carotenoid-like profile with a three-shoulder absorption peak, while Fourier transform infrared (FT-IR) spectroscopy and high-resolution liquid chromatography mass spectrophotometry (HR-LCMS) analysis confirmed the presence of yellow carotenoid pigment consistent with zeaxanthin (C40H56O2), along with additional unidentified peaks. To enhance the pigment yield, we employed a multi-stage optimization strategy beginning with one-factor-at-a-time, followed by response surface methodology (RSM), which resulted in ∼200% increases in pigment dry weight from 26 mg/100 mL to 78 mg/100 mL. Further supplementation of RSM media with TiO2 nanomaterials provided an additional ∼30% increase, achieving 102 mg/100 mL. Overall, the optimized conditions resulted in a ∼3.9-fold improvement compared to basal media. Early findings demonstrate that MDCK cells exhibit no negative response to the pigment, highlighting its promise for textile dyeing applications. This research demonstrates the successful isolation of an Arctic Citricoccus-like strain and systematic optimization of its carotenoid pigment yield, providing preliminary evidence of its biotechnological potential, particularly for textile coloration.