Title : Phaffia brasiliana as a natural source of astaxanthin for aquaculture
Abstract:
Carotenoid pigments play an important role in aquaculture due to their well-known contributions in enhancing coloration, oxidative stability, and overall fish health. Among them, astaxanthin stands out as one of the most powerful natural antioxidants described to date, exhibiting strong free-radical neutralizing activity and promoting improved pigmentation of muscle in food fish and skin color in ornamental fish. Species of the genus Phaffia have been reported as natural producers of astaxanthin and other related carotenoids, making them promising biological sources for aquaculture applications. Thus, it was evaluated the in vitro antioxidant profile of the yeast Phaffia brasiliana UFMG-CM-6497 and analyzed its effects when administered as a dietary supplement to Nile tilapia (Oreochromis niloticus) for 63 days in Biofloc (BFT) and Clear Water (CW) systems. High antioxidant activity in vitro was demonstrated for all the methods tested: Folin-Ciocalteu (69.76 mg GAE/100 g), DPPH (5.37 mg/mL), and β-carotene/linoleic acid bleaching (64.55% protection). Moreover, carotenoid identification and quantification by HPLC-DAD-MS revealed the presence of a diverse array of pigments, including astaxanthin isomers (50.72 µg/g; 6.56%), β-carotene (78.80 µg/g; 10.19%), β-zeacarotene isomers (79.59 µg/g; 10.29%), phytoene (417.29 µg/g; 53.95%), and phytofluene (58.35 µg/g; 7.54%). Due to their different intrinsic antioxidant capacities, the weighted contribution of each carotenoid to the total antioxidant activity of the yeast was evaluated, revealing a predominant role of astaxanthin isomers (507.2), especially when considering their lower relative concentration compared to other more abundant compounds – phytoene (208.645), β-zeacarotene isomers (79.59), and β-carotene (78.8). When administered in vivo to Nile tilapia, although all values remained within the species-specific reference ranges, a significant effect on the yeast-supplemented groups (Y) (CW-Y and BFT-Y) was observed (p<0.05) on some hematological parameters, including higher erythrocyte counts (1.85 106/mm3 and 1.60 106/mm3) and hematocrit (38.13% and 34.54%), when compared to controls (C) (CW-C: 1.07 106/mm3 and 24.08%; BFT- C: 1.10 106/mm3 and 20.83%). Furthermore, considering serum glucose as a stress biomarker, this parameter remained stable (p>0.05) and within the recommended range for the species across all groups during the postprandial period, ranging from 82.92 mg/dL to 101.42 mg/dL (CW-Y/BFT-Y) and 87.17 mg/dL to 83.25 mg/dL (CW-C/BFT-C). Moreover, a significant difference (p<0.05) in fillet coloration was observed in the yeast-supplemented groups compared to their respective controls, with increased fillet redness (a* values) – CW-Y (11.40), BFT-Y (13.65), CW-C (10.47), and BFT-C (13.11). Also, considering in vitro antioxidant activity analysis, such as β-carotene bleaching, fillet redness is determined not only by pigment accumulation but also by the yeast’s antioxidant activity, which can protect carotenoids from metabolic degradation and facilitate their incorporation into muscle. Altogether, these findings demonstrate the potential of P. brasiliana UFMG-CM-6497-derived carotenoids, especially astaxanthin, as functional supplementation in aquaculture feeds, offering a natural and biological source for improving fish pigmentation and oxidative stress regulation.
