Pigment Production Improvement in Rhodotorula mucilaginosa AJB01 Using Design of Experiments

The discovery of biopigments has received considerable attention from the industrial sector, mainly for potential applications as novel molecules with biological activity, in cosmetics or if aquaculture food supplements. The main objective of this study was to increase the production of carotenoid pigments in a naturally pigmented yeast by subjecting the yeast to various cellular stresses using design of experiments. The fungal strain Rhodotorula mucilaginosa AJB01 was isolated from a food sample collected in Barranquilla, Colombia, and one of the pigments produced was β-carotene. This strain was subjected to various stress conditions, including osmotic stress using different salts, physical stress by ultraviolet (UV) light, and light stress using different photoperiods. The optimal growth conditions for carotenoid production were determined to be 1 min of UV light, 0.5 mg/L of magnesium sulfate, and an 18:6 h light/dark period, which resulted in a carotenoid yield of 118.3 µg of carotenoid per gram of yeast.

Raspberry-Like Microspheres of Core-Shell Cr2 O3 @TiO2 Nanoparticles for CO2 Photoreduction

To promote the interaction of p-n semiconductors, raspberry-like microspheres of core-shell Cr2 O3 @TiO2 nanoparticles have been fabricated through a five-step process. Raman spectroscopy of products calcined at various temperatures reveal that the titania shell causes crystal distortion of the Cr2 O3 core, without changing the microstructures of the fabricated core-shell microspheres. In situ and time-resolved synchrotron-based powder XRD reveals the formation of monoclinic TiO2 in the fourth step, but these monoclinic TiO2 nanocrystals undergo a phase transition when the applied calcination temperature is above 550 °C. As a result, TiO2 (B), a magnéli phase of Ti4 O7 and Cr2 Ti6 O15 compounds, resulting from inner doping between Cr2 O3 and TiO2 , is formed. The close interaction of Cr2 O3 and TiO2 forms a p-n junction that decreases the recombination of photogenerated electron-hole pairs, leading to enhanced production of CH4 by photocatalytic reduction of CO2 .