Rhodosporidium toruloides, a type of red yeast, is gaining significant attention in various scientific and industrial fields. This microorganism belongs to the Basidiomycota phylum, Microbotryomycetes class, Sporidiobolales order, and Sporidiobolaceae family. It was first identified in 1922 and is widely distributed in natural environments, including soil, seawater, and plant leaves.
Distinctive Biological Features
Rhodosporidium toruloides is recognized for its remarkable capacity to accumulate large amounts of lipids within its cells, a characteristic that classifies it as an oleaginous yeast. These stored lipids, primarily triacylglycerides, can constitute over 70% of the yeast’s dry cell weight, making them comparable to traditional vegetable oils. This high lipid content is important for its biotechnological uses.
The yeast also synthesizes various carotenoids, which are vibrant pigments and powerful antioxidants. These include beta-carotene, torulene, and torularhodin. Torulene and torularhodin exhibit even more potent antioxidant properties.
R. toruloides displays significant metabolic versatility. It can utilize a wide array of carbon sources for growth and production, including various monosaccharides like glucose and xylose, oligosaccharides such as sucrose and maltose, alcohols like glycerol, and even organic acids like acetate. This adaptability allows it to thrive in diverse growth conditions, including those containing inhibitors found in industrial waste streams.
Producing Valuable Compounds
Its substantial lipid accumulation allows for the production of Single-Cell Oil (SCO). This microbial oil is extracted and refined, serving as a sustainable and renewable alternative to conventional plant or animal-derived oils. SCO from R. toruloides is a promising feedstock for various industrial applications due to its high yield and favorable fatty acid composition.
The yeast also yields natural pigments and antioxidants. Its carotenoid biosynthesis pathway produces compounds such as beta-carotene, torulene, and torularhodin. These carotenoids provide vibrant colors and strong antioxidant activities.
R. toruloides can produce other metabolites, including enzymes and organic acids. It can generate fatty alcohols, which are derivatives of fatty acids, and unusual fatty acids like punicic acid. These diverse compounds broaden its applications.
Current and Emerging Applications
The lipids produced by Rhodosporidium toruloides are used for conversion into advanced biofuels, such as biodiesel and bio-jet fuel. These microbial lipids can be derived from renewable, low-cost feedstocks like agricultural and forestry waste, offering a sustainable alternative to fossil fuels.
In the food and feed industries, R. toruloides carotenoids are used as colorants, for example, in poultry feed to enhance egg yolk color or in aquaculture to intensify the pigmentation of salmon and other seafood. The yeast is also a source of single-cell protein and nutritional supplements, offering a sustainable protein alternative.
Carotenoids from R. toruloides are used in the cosmetics and pharmaceutical sectors due to their antioxidant and health-promoting properties. These natural antioxidants are incorporated into skincare products and anti-aging formulations.
Bioremediation is another application for R. toruloides. Its metabolic versatility allows it to break down pollutants and convert waste materials into valuable products. It can consume lignocellulosic biomass and tolerate inhibitory compounds present in industrial waste streams, making it a sustainable option for waste valorization and the development of circular bioeconomy models.