Rhodosporidium toruloides: a new platform organism for conversion of lignocellulose into terpene biofuels and bioproducts

Abstract

BackgroundEconomical conversion of lignocellulosic biomass into biofuels and bioproducts is central to the establishment of a robust bioeconomy. This requires a conversion host that is able to both efficiently assimilate the major lignocellulose-derived carbon sources and divert their metabolites toward specific bioproducts.ResultsIn this study, the carotenogenic yeast Rhodosporidium toruloides was examined for its ability to convert lignocellulose into two non-native sesquiterpenes with biofuel (bisabolene) and pharmaceutical (amorphadiene) applications. We found that R. toruloides can efficiently convert a mixture of glucose and xylose from hydrolyzed lignocellulose into these bioproducts, and unlike many conventional production hosts, its growth and productivity were enhanced in lignocellulosic hydrolysates relative to purified substrates. This organism was demonstrated to have superior growth in corn stover hydrolysates prepared by two different pretreatment methods, one using a novel biocompatible ionic liquid (IL) choline α-ketoglutarate, which produced 261 mg/L of bisabolene at bench scale, and the other using an alkaline pretreatment, which produced 680 mg/L of bisabolene in a high-gravity fed-batch bioreactor. Interestingly, R. toruloides was also observed to assimilate p-coumaric acid liberated from acylated grass lignin in the IL hydrolysate, a finding we verified with purified substrates. R. toruloides was also able to consume several additional compounds with aromatic motifs similar to lignin monomers, suggesting that this organism may have the metabolic potential to convert depolymerized lignin streams alongside lignocellulosic sugars.ConclusionsThis study highlights the natural compatibility of R. toruloides with bioprocess conditions relevant to lignocellulosic biorefineries and demonstrates its ability to produce non-native terpenes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0927-5) contains supplementary material, which is available to authorized users.

A toolset of constitutive promoters for metabolic engineering ofRhodosporidium toruloides

“…We selected 29 R. toruloides promoters, based on transcriptomics studies, and examined them in four different media over seven days using a dual-reporter system. P GAPDH is one of the most widely used promoters for engineering a variety of yeasts, including R. toruloides, where it was employed for expression of heterologous terpene synthases [1].…”

“…Three confirmed transformants for each construct were inoculated into 24-deep-well plates containing LB medium, grown overnight, and then subcultured into the various test media at a starting OD 600 of 0.05. One rich medium (YPD) and three defined media (SD supplemented with 1% glucose, 1% xylose, or 1% of each sugar) were selected to represent typical media compositions [1] to culture R. toruloides ( Figure 1C).…”

“…So far, much of the work on metabolic engineering or bioproduct formation in R. toruloides has focused on lipid accumulation [2,3]. However, the high lipid content indicates a suitability for applications to any acetyl-CoA-derived product, from fatty alcohols and methyl ketones to terpenes, with many applications such as fuels, chemicals, and pharmaceuticals [1,[4][5][6].…”

Challenges in lipid production from lignocellulosic biomass using Rhodosporidium sp.; A look at the role of lignocellulosic inhibitors

“…Although it has been demonstrated that the strains of the genus Rhodosporidium tolerate a wide range of pH values (2.2–7.5), it has been found that this parameter has a significant effect at low (pH = 4), intermediate (pH = 5.5) and high (pH = 7) values with respect to the accumulation of biomass (13.5, 16 and 10 g L −1 respectively), lipid yield (4, 6.4 and 2.5 g L −1 respectively), and lipid content with respect to its biomass (32%, 38%, and 27% respectively) . Yaegashi, found that the pH of the culture medium was an important factor for the efficient use of fermentable sugars in the conversion of lignocellulosic hydrolysates to terpenes by a genetically modified strain of R. toruloides . In this investigation, they reported the maximum production of terpene by this strain at low pHs (3.4), which suggested that the strain was susceptible to produce organic acids in a native way.…”

Exploiting nonionic surfactants to enhance fatty alcohol production in Rhodosporidium toruloides

“…The global energy crisis and environmental concerns surrounding nonrenewable energy production have increased the interest in alternative sustainable routes to the production of renewable fuels and chemicals (Peralta‐Yahya, Zhang, del Cardayre, & Keasling, 2012; Yaegashi et al, 2017). At present, biodiesel, surfactants, and lubricants are mostly produced from animal fat and vegetable oils (Fillet et al, 2015).…”