LAUSR

Ketocarotenoids are high-value natural pigments. The red diketocarotenoid astaxanthin particularly exhibits an extraordinary antioxidant activity, which raises its market demand for foods and nutraceuticals. We screened for ketocarotenoid-producing bacteria from both marine and freshwater environments. Phylogenetic analysis, based on 16S rRNA gene sequence, revealed 37 potential producers of ketocarotenoids that are related to α-proteobacteria, comprising 32 strains of Brevundimonas and 5 strains of Erythrobacter. Carotenoids analysis by HPLC-DAD and HPLC-MS revealed two groups; astaxanthin-producers (28 Brevundimonas strains) and adonixanthin-producers (Five Brevundimonas and 5 Erythrobacter strains). Strain FrW-Asx16 exhibited the highest carotenoid production (1060 µg g-1 dry cells with 16.6% astaxanthin). Strain FrW-Asx-5 producing 946.1 µg g-1 dry cells carotenoid exhibited the highest astaxanthin content (∼46%). The most intriguing result is the potential of producing natural colorants from freshwater bacterial isolates, and with high productivity and selectivity, suggesting a great promise for their application in food.