Production Optimization and Evaluation of Antioxidant and Cytotoxic Properties of Cellulosimicrobium AZ Carotenoid Pigment

The radiation-resistant extremophile microorganisms can produce high amounts of carotenoids. However, the optimization of their metabolite production is critical for large-scale commercial purpose. This study aimed to investigate the production of carotenoid pigments by an extremophile strain phylogenetically close to the genus Cellulosimicrobium that has not been reported so far.

The influence of various carbon and nitrogen sources on the microbial biomass and pigment production of the studied strain were investigated using one-factor-at-a-time-approach. Antioxidant activity of the pigment was evaluated using free radical scavenging and ferric reducing antioxidant power. Besides, the antibacterial and cytotoxicity activity of the pigment extract were investigated using the agar well-diffusion method and cell metabolic activity assay, respectively.

The maximum amount of carotenoid pigment produced by the studied strain was achieved in the fermentation medium containing 1g/L yeast extract and 1g/L glucose (22.5 mg /L) that was 10.7 fold more than the unoptimized conditions (2.1 mg/L). The half-maximal effective concentration (EC50) values of the pigment were evaluated as much as 10.97 mg/mL and 6.02 μg/mL in the free radical scavenging and ferric reducing antioxidant power assay, respectively. Also, the pigments of this strain showed no toxic and inhibitory effect on the human fibroblast cell line.

As compared to previous studies, the carotenoid pigment extract of strain AZ displayed strong antioxidant activity. Therefore, the present study lays a foundation for future utilizations of Cellulosimicrobium strain AZ as a promising microorganism for commercial production of carotenoids in the food industry or sunscreens due to the antioxidant and non-cytotoxic activity of its carotenoid pigment.