Rhodotorula toruloides: an ideal microbial cell factory to produce oleochemicals, carotenoids, and other products

Requirement of clean energy sources urges us to find substitutes for fossil fuels. Microorganisms provide an option to produce feedstock for biofuel production by utilizing inexpensive, renewable biomass. Rhodotorula toruloides (Rhodosporidium toruloides), a non-conventional oleaginous yeast, can accumulate intracellular lipids (single cell oil, SCO) more than 70% of its cell dry weight. At present, the SCO-based biodiesel is not a price-competitive fuel to the petroleum diesel. Many efforts are made to cut the cost of SCO by strengthening the performance of genetically modified R. toruloides strains and by valorization of low-cost biomass, including crude glycerol, lignocellulosic hydrolysates, food and agro waste, wastewater, and volatile fatty acids. Besides, optimization of fermentation and SCO recovery processes are carefully studied as well. Recently, new R. toruloides strains are developed via metabolic engineering and synthetic biology methods to produce value-added chemicals, such as sesquiterpenes, fatty acid esters, fatty alcohols, carotenoids, and building block chemicals. This review summarizes recent advances in the main aspects of R. toruloides studies, namely, construction of strains with new traits, valorization of low-cost biomass, process detection and optimization, and product recovery. In general, R. toruloides is a promising microbial cell factory for production of biochemicals.