Sustainable production of sarcinaxanthin by Kocuria palustris using agro- industrial residues: optimization and evaluation of photoprotective and antioxidant activities

Carotenoids are natural pigments lipophilic natural pigments and have a wide range of biotechnological applications. This study aimed to produce carotenoids by cultivating Kocuria palustris on alternative substrates the selected condition was subsequently applied to process scale-up the selected cultivation conditions were subsequently used for process scale-up the selected cultivation conditions were subsequently used for process scale-up and to evaluate the photoprotective and antioxidant activities of the resulting extract. Production was carried out using a 2² factorial design to evaluate the effects of glucose and Tangerine Peel Juice (TPJ) concentrations, while maintaining a constant whey concentration, on biomass production, total carotenoids, specific carotenoids, and Sun Protection Factor (SPF). Preliminary characterization of the pigments by spectrophotometry revealed an absorption profile compatible with sarcinaxanthin. Fourier Transform Infrared Spectroscopy (FTIR) revealed functional groups consistent with carotenoid structures, while Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) provided complementary information on the morphology and elemental composition of the extract. The experimental design demonstrated that supplementation of the residual medium with glucose and Citrus reticulata peel significantly enhanced carotenoid production and SPF. The selected cultivation conditions were subsequently used for process scale-up, during which K. palustris maintained its carotenoid-producing capacity in a medium formulated with alternative agro-industrial substrates. The extract exhibited high photoprotective activity, reaching an SPF of 41.21. However, given the complex composition of the extract, this activity could not be attributed exclusively to the carotenoids produced by the bacterium. In addition, the extract exhibited antioxidant activity ranging from 31.82 to 61.36% in the β-carotene/linoleic acid system, with no dose-dependent behavior across the concentrations evaluated. In conclusion, K. palustris shows potential for the sustainable production of carotenoids with a profile compatible with sarcinaxanthin using alternative agro-industrial substrates. Process scale-up and the photoprotective and antioxidant properties of the extract support the potential for further development of this bioprocess. These findings are particularly relevant to the cosmetic and biotechnology industries, where there is growing interest in natural pigments and bioactive compounds obtained through more sustainable production routes.