Improvement of high-added value carotenoid production from Rhodotorula glutinis CCT-2186 yeasts: A biorefinery perspective

Biorefining is a sustainable processing approach for the conversion of biomass into multiple valuable bioproducts through an integrated platform. Rhodotorula strains can produce various bioproducts i.e., carotenoids and lipids, make it a potential microorganism for application in a biorefinery concept. With this in mind, here the production of carotenoids, β-carotene, torularhodin, torulene, and lipids by Rhodotorula glutinis is evaluated. Two statistical experimental designs were applied to enhance carotenoid production: a first 25-1 fractional factorial design to evaluate the influence of independent variables pH, nitrogen source (organic or inorganic), glucose, KH2PO4 and MgSO4; and a second 22 central factorial design to optimize the pH and nitrogen sources. After the 22 factorial design optimization, R. glutinis was able to produce 297.84 µg/mL of β-carotene, 286.06 µg/mL of torularhodin and 37.35 µg/mL of torulene, with low nutritional requirements of glucose (10 g/L) and nitrogen content (organic-10 g/L; inorganic-4 g/L). Moreover, 45% (m/m) of the R. glutinis biomass corresponded to lipid content. After the optimization, the process was scaled-up to a 5L stirred-tank bioreactor. Switching to a bioreactor allowed and improvement of aeration and agitation conditions, which led to an increase in production yield (m/v) of, approximately, 25.83%, 11.88%, 24.50%, 12.40% and 40.31% for β-carotene, torularhodin, torulene and lipids, respectively. R. glutinis is a promising source of carotenoids and lipids in the production of high-value compounds for nutritional and pharmaceutical applications, making it a promising host for use in a biorefinery approach.