Natural lycopene and 8-carotene synthesis by Rhodosporidium kratochvilovae yeasts: Sustainable production, chemical characterization and antioxidative properties

Two yeast strains, Rhodosporidium kratochvilovae Y-42 and Y-43, were evaluated for their ability to synthesize natural carotenoids through submerged fermentations, using cheese whey (CW). Initially, CW was hydrolyzed with commercial 8-galactosidase to yield glucose and galactose and the subsequent fermentations with R. kratochvilovae Y-42 and Y-43 led to the production of 1.87 and 1.64 mg/L of total carotenoids, respectively. HPLC-DAD analysis of the chemical profile indicated that 8-carotene was the predominant carotenoid. Conversely, when CW hydrolysis occurred using fermented wheat bran, which also served as source of free amino nitrogen (FAN), both yeasts synthesized almost solely lycopene. Lycopene production was investigated under different C/FAN ratios (40 and 60 g/g) and incubation temperatures (23, 28 and 33 degrees C). Under the optimized culture conditions yeast strain Y-42 produced 36.4 mg/L carotenoids, composed of more than 97% of lycopene, highlighting the substantial role of media in carotenoids synthesis and composition. Moreover, the lycopene-rich carotenoid extract exhibited antioxidant activity (IC50 equal to 0.89 mg/mL), signifying also the possibility to be further used as a functional additive in novel food formulations. Evidently, this study showed for the first time that Rhodosporidium kratochvilovae can naturally produce lycopene using renewable resources, thus reinforcing the shift towards sustainable food production.