Enhancement of astaxanthin production in novel red yeast Rhodosporidiobolus sp. SP3-3/4 and genomic characterization

Abstract

Astaxanthin is a red carotenoid and potent antioxidant with anti-inflammatory, anti-cancer, neuroprotective, and immuno-enhancing benefits. This study focused on enhancing astaxanthin production using a novel red yeast, strain SP3-3/4, through genomic analysis. Strain SP3-3/4 shared 99.66% sequence identity in the D1/D2 domain of the large subunit rRNA gene with Rhodosporidiobolus ruineniae CBS 5001T. Whole-genome analysis indicated 82.54% similarity to R. ruineniae JCM 8097T, with average nucleotide identity (ANI) values below 80% for other strains. The ANI result, lower than the 95% cutoff, confirms SP3-3/4 as a novel species, Rhodosporidiobolus sp. SP3-3/4. Key astaxanthin synthesis genes, including CrtE, CrtYB, CrtI, CrtS, CrtR, CrtW, CrtO, and CrtZ, were annotated. Astaxanthin production was verified using HPLC and LC-MS. Optimization of medium composition and physical parameters identified optimal conditions as 20 g/L sucrose, 3 g/L yeast extract, and 5 g/L peptone, with an initial medium pH of 6.5. Maximum cell growth and astaxanthin content, reaching 9.615 g/L and 0.46 mg/g DCW, respectively, were achieved after 5 days of cultivation, corresponding to an astaxanthin yield of 6.93 mg/L and a productivity rate of 1.39 mg/L/day. Notably, a maximum productivity of 1.45 mg/L/day occurred in 3 days. These findings elucidated comprehensive optimization of astaxanthin production, incorporating functional genomic assessment and analysis of protein-encoded genes of astaxanthin-producing yeast Rhodosporidiobolus sp. SP3-3/4. Such insights represent valuable biological resources with significant implications for diverse biotechnological and bioinformatics applications.