Lipid production in batch and fed-batch cultures of Rhodosporidium toruloidesfrom 5 and 6 carbon carbohydrates

Abstract

BackgroundMicrobial lipids are a potential source of bio- or renewable diesel and the red yeast Rhodosporidium toruloides is interesting not only because it can accumulate over 50% of its dry biomass as lipid, but also because it utilises both five and six carbon carbohydrates, which are present in plant biomass hydrolysates.MethodsR. toruloides was grown in batch and fed-batch cultures in 0.5 L bioreactors at pH 4 in chemically defined, nitrogen restricted (C/N 40 to 100) media containing glucose, xylose, arabinose, or all three carbohydrates as carbon source. Lipid was extracted from the biomass using chloroform-methanol, measured gravimetrically and analysed by GC.ResultsLipid production was most efficient with glucose (up to 25 g lipid L−1, 48 to 75% lipid in the biomass, at up to 0.21 g lipid L−1 h−1) as the sole carbon source, but high lipid concentrations were also produced from xylose (36 to 45% lipid in biomass). Lipid production was low (15–19% lipid in biomass) with arabinose as sole carbon source and was lower than expected (30% lipid in biomass) when glucose, xylose and arabinose were provided simultaneously. The presence of arabinose and/or xylose in the medium increased the proportion of palmitic and linoleic acid and reduced the proportion of oleic acid in the fatty acids, compared to glucose-grown cells.High cell densities were obtained in both batch (37 g L−1, with 49% lipid in the biomass) and fed-batch (35 to 47 g L−1, with 50 to 75% lipid in the biomass) cultures. The highest proportion of lipid in the biomass was observed in cultures given nitrogen during the batch phase but none with the feed. However, carbohydrate consumption was incomplete when the feed did not contain nitrogen and the highest total lipid and best substrate consumption were observed in cultures which received a constant low nitrogen supply.ConclusionsLipid production in R. toruloides was lower from arabinose and mixed carbohydrates than from glucose or xylose. Although high biomass and lipid production were achieved in both batch and fed-batch cultures with glucose as carbon source, for lipid production from mixtures of carbohydrates fed-batch cultivation was preferable. Constant feeding was better than intermittent feeding. The feeding strategy did not affect the relative proportion of different fatty acids in the lipid, but the presence of C5 sugars did.

Corecovery of lipids and fermentable sugars from Rhodosporidium toruloides using ionic liquid cosolvents: Application of recycle to batch fermentation

“…Batch two produced qualitatively similar results but with the xylose fully consumed, Figure . Both batch one (no recycle) and batch two (with recycle) achieved similar final cell mass densities [9.1 (±0.2) gdw/L for batch one vs. 9.4 (±0.2) gdw/L for batch two] that are in line with previous reports . The biomass to lipid yields ( Y P/X ) for batch one and two were also similar at approximately 60.5 (±1.5) and 57.4 (±0.3)% (% w/w, whole dried cell mass), respectively, and equivalent to those reported by Wiebe et al for batch culture under similar conditions (∼56% w/w, whole yeast), indicating that the batch culture conditions were appropriate for lipid production.…”

“…The results for batches one and two are presented in Table and Figure . Batch one (without recycle) reached a maximum cell mass density of approximately 9.1 (±0.2) gdw/L, a value comparable to previous reports performed under similar conditions using simple carbohydrate feeds such as glucose . As expected, R. toruloides consumed xylose only after glucose depletion, Figure .…”

A new combined approach to improved lipid production using a strictly aerobic and oleaginous yeast

“…High oxygen availability culture had improvements in all parameters, particular in lipid content increase to 52% w/w and achieved a biomass of 2.49 g/L ( Table 1). For R. toruloides, the Y L/S frequently documented for oleaginous microorganisms is around 0.20 g/g [10,11,44,56]. Although, the Y L/S obtained are consistent with the values referenced by other authors, with a similar initial glucose concentration, these values are low relative to the theoretical maximum.…”

Identification of oleaginous yeast strains able to accumulate high intracellular lipids when cultivated in alkaline pretreated corn stover

“…Lipids produced by yeasts have similar fatty acid profiles to those of vegetable oils. However, the high cost of synthetic culture media makes microbial oils less economically viable (Chen et al 2009; Huang et al 2013a; Wiebe et al 2012). Recent work on the ability of yeasts to grow and utilize wastes materials and accumulate carbon as lipids, have suggested the possibility of producing oleochemicals including biodiesel from lignocellulosic hydrolysates, which are the product of pretreatment followed by enzymatic hydrolysis of lignocellulosic biomass (Huang et al 2013a; Zhu et al 2008).…”