Carbon/nitrogen ratio as a tool to enhance the lipid production in Rhodosporidium toruloides-1588 using C5 and C6 wood hydrolysates

The interest in microbial lipids has recently increased because of their wide use to produce several value-added compounds in the biofuel, pharmaceutical and food industries. Oleaginous yeast such as Rhodosporidium tor-uloides could be an efficient option because of its ability to consume five-carbon sugars, high lipid accumulation, and tolerance to toxic compounds such as furans, phenolic compounds, and organic acids. The present study aims to investigate the effect of different initial sugar ratios, in combination with different carbon/nitrogen ratios, and the use of dibasic sodium phosphate (Na2HPO4) as an inducer on cell biomass production, sugar consumption, and lipid accumulation by Rhodosporidium toruloides-1588. The investigation showed a maximum lipid accu-mulation of 5.35 gL-1 (0.28 g of lipids/g of sugar) under the culture conditions of initial glucose: xylose ratio of 1:1, C/N ratio of 70, and Na2HPO4 concentration of 1.05 gL-1. The predominant lipids composition was palmitic, stearic, oleic, and linoleic acids which could be used as a suitable feedstock for biofuel production. Additionally, under the optimal conditions (initial glucose: xylose ratio of 1:1, 1.19 gL-1 of Na2HPO4 and C/N ratio of 70.50) an increase of 10.5% and 7.5% in lipid accumulation was observed, compared with control treatments (glucose and xylose, respectively). In addition, the study shows the ability of R. toruloides-1588 to tolerate inhibitors, a feature that could be a promising alternative to increase the feasibility of the microbial lipid production process using undetoxified wood hydrolysate as a sustainable culture media.