Rhodosporidium toruloides cultivated in NaCl‐enriched glucose‐based media: Adaptation dynamics and lipid production

Abstract

In the present report and for the first time in the international literature, the impact of the addition of NaCl upon growth and lipid production on the oleaginous yeast Rhodosporidium toruloides was studied. Moreover, equally for first time, lipid production by R. toruloides was performed under nonaseptic conditions. Therefore, the potentiality of R. toruloides DSM 4444 to produce lipid in media containing several initial concentrations of NaCl with glucose employed as carbon source was studied. Preliminary batch‐flask trials with increasing amounts of NaCl revealed the tolerance of the strain against NaCl content up to 6.0% w/v. However, 4.0% w/v of NaCl stimulated lipid accumulation for this strain, by enhancing lipid production up to 71.3% w/w per dry cell weight. The same amount of NaCl was employed in pasteurized batch‐flask cultures in order to investigate the role of the salt as bacterial inhibiting agent. The combination of NaCl and high glucose concentrations was found to satisfactorily suppress bacterial contamination of R. toruloides cultures under these conditions. Batch‐bioreactor trials of the yeast in the same media with high glucose content (up to 150 g/L) resulted in satisfactory substrate assimilation, with almost linear kinetic profile for lipid production, regardless of the initial glucose concentration imposed. Finally, fed‐batch bioreactor cultures led to the production of 37.2 g/L of biomass, accompanied by 64.5% w/w of lipid yield. Lipid yield per unit of glucose consumed received the very satisfactory value of 0.21 g/g, a value among the highest ones in the literature. The yeast lipid produced contained mainly oleic acid and to lesser extent palmitic and stearic acids, thus constituting a perfect starting material for “second generation” biodiesel.

Feasibility of Lipid Production from Waste Paper by the Oleaginous Yeast Cryptococcus curvatus

“…The high lipid yields that ranged from 201.4 mg/g to 224.4 mg/g suggested that carbon sources in the hydrolysates were mainly channeled into lipid biosynthesis. These data were comparable to those obtained by Yarrowia lipolytica and Rhodosporidium toruloides on glucose (Qiao et al 2015;Tchakouteu et al 2017). Overall, the authors' results indicated that waste paper hydrolysates could serve as appealing substrates for lipid production.…”

Lipids from yeasts and fungi: physiology, production and analytical considerations

“…a,b (data from Tchakouteu et al . ). It can be easily become understandable that onset of lipid accumulation was given only after remarkable exhaustion of the assimilable nitrogen found into the culture medium and, thereafter, large quantities of microbial lipids (in both absolute; g l −1 , and relative; % in DCW, values) were accumulated inside the yeast cells.…”

“…T. elegans 14Á9 3 4 Á5 Flasks Zikou et al (2013) interesting alternative to the use of plant oils for biodiesel production because oleaginous yeasts, due to their unicellular morphology can be cultivated more easily than the fungi in large-scale bioreactors, whereas strains of these yeasts can transform a variety of substrates including low-or even zero-cost materials to SCO, which can then be transformed to biodiesel (Xue et al 2006;Li et al 2007;Zhao et al 2008;Li et al 2010;Xu et al 2012Xu et al , 2013Xu et al , 2016Xu et al , 2017Tsakona et al 2014Tsakona et al , 2016Karamerou et al 2015;Louhasakul and Cheirsilp, 2013;Tchakouteu et al 2015aTchakouteu et al , 2017Karamerou et al 2017). It is evident that as far as the synthesis of SCO that is aimed to be transformed in second-generation biodiesel is concerned, only hydrophilic carbon sources (i.e.…”

“…Kinetic analysis of lipid accumulation process in a characteristic oleaginous microorganism (R. toruloides DSM 4444) during growth on sugar-based nitrogen-limited media is presented in Fig. 2a,b (data from Tchakouteu et al 2017). It can be easily become understandable that onset of lipid accumulation was given only after remarkable exhaustion of the assimilable nitrogen found into the culture medium and, thereafter, large quantities of microbial lipids (in both absolute; g l À1 , and relative; % in DCW, values) were accumulated inside the yeast cells.…”

“…Culture conditions: growth on batch bioreactor, agitation speed 200-500 rev min À1 , pH = 6Á0 AE 0Á1, aeration 1 vvm, DOT>20% (v/v), incubation temperature T = 26°C. Data from Tchakouteu et al (2017).…”