Red Yeast Rhodotorula Glutinis Research Articles

A chromosome-scale genome provides new insights into the typical carotenoid biosynthesis in the important red yeast Rhodotorula glutinis QYH-2023 with anti-inflammatory effects

Rhodotorula spp. has been studied as one powerful source for a novel cell factory with fast growth and its high added-value biomolecules. However, its inadequate genome and genomic annotation have hindered its widespread use in cosmetics and food industries. Rhodotorula glutinis QYH-2023, was isolated from rice rhizosphere soil, and the highest quality of the genome of the strain was obtained at chromosome level (18 chromosomes) than ever before in red yeast in this study. Comparative genomics analysis revealed that there are more key gene copies of carotenoids biosynthesis in R. glutinis QYH-2023 than other species of Rhodotorula spp. Integrated transcriptome and metabolome analysis revealed that lipids and carotenoids biosynthesis was significantly enriched during fermentation. Subsequent investigation revealed that the over-expression of the strain three genes related to carotenoids biosynthesis in Komagataella phaffii significantly promoted the carotenoid production. Furthermore, in vitro tests initially confirmed that the longer the fermentation period, the synthesized metabolites controlled by R. glutinis QYH-2023 genome had the stronger anti-inflammatory properties. All of the findings revealed a high-quality reference genome which highlight the potential of R. glutinis strains to be employed as chassis cells for biosynthesizing carotenoids and other active chemicals.

Detailed mechanistic investigation of stress-induced lipogenesis in oleaginous yeast for value-added metabolites

In the present study, a marine red yeast Rhodotorula glutinis ISO A1 cultivated under combinations of artificial seawater (ASW) and sewage wastewater (SWW) has been subjected to detailed mechanistic investigations via physiological and biochemical analysis to dissect the pathway of halotolerance behavior and carbon flux channelization towards enhanced lipid synthesis. Amid all tested groups (25–100% ASW), cells grown in 25% ASW yielded ∼ 1.4-fold higher lipid yield than glucose synthetic medium (GSM) and revealed metabolic rewiring of cells to channelize carbon pools for producing neutral lipids of vehicular quality. Detailed carbohydrate profiling showed enhanced glycerol, trehalose, mannose, and xylitol/arabitol under saline stress, suggesting the interplay of these metabolites to impart tolerance against osmotic imbalance. Further, the strengthened enzymatic activity (glutathione reductase, superoxide dismutase, ascorbate peroxidase) and non-enzymatic metabolites (betaine, proline) highlighted the active yeast defence network to counter altered redox state arise due to high salinity. The stress-induced responses also constituted substantial variations in membrane fluidity and production of biodiesel-quality lipids. Further findings like low thermal degradation temperature (at ∼ 265°C) and high chitin (can be converted into chitosan) entity in yeast de-oiled biomass primarily derived from yeast cells grown under contaminated environment; sea and sewage wastewater, signified its potential utilization for chitosan recovery, a commercially important product. Conclusively, this study elucidated a competent model of yeast-based biorefinery approach integrating seawater-wastewater utilization and simultaneous production of biodiesel and value-added products vital for a sustainable and circular bioeconomy.

Effects of TiO2 and H2O2 treatments on the biosynthesis of carotenoids and lipids in oleaginous red yeast Rhodotorula glutinis ZHK

Microbial carotenoids and lipids are two groups of versatile biomolecules widely used in the food, fuel, pharmaceutical, and cosmetic industries. Rhodotorula glutinis is one of the best-known oleaginous red yeasts that has the remarkable capability to produce an assortment of valuable carotenoids and lipids. Here, the effects of different concentrations of TiO2 and H2O2 treatments on carotenoid and lipid production in R. glutinis ZHK were investigated. After 120 h of cultivation, the total amount of carotenoids was significantly increased in the TiO2 (100 mg/L: 23.165 μg/gdw, 750 mg/L: 19.65 μg/gdw) and H2O2 (5 mM: 21.51 μg/gdw, 10 mM: 118.858 μg/gdw) treatments than the control (6.099 μg/gdw). In contrast, as compared to the control, the relative abundance of total lipids was significantly decreased in the TiO2 (100 mg/L) and H2O2 (10 mM) treatments, respectively. In response to TiO2 and H2O2 stresses, the increased carotenoids were probably attributed to the down-regulated lipid biosynthesis flux, while the decreased lipids might be ascribed to the down-regulated fatty acid biosynthesis flux. Our results presented herein not only provide an effective strategy for modulating carotenoid and lipid biosynthesis in R. glutinis ZHK but also reveal the molecular foundation to further enhance their bioproductivity by molecular manipulation.

Bioconversion of sugarcane molasses and waste glycerol on single cell oils for biodiesel by the red yeast Rhodotorula glutinis R4 from Antarctica

• R. glutinis R4 produce singe cell oil (SCO) from cane molasses and waste glycerol. • The fatty acids composition of SCO from R4 is suitable for biodiesel production. • SCO from R. glutinis R4 were transformed into biodiesel with a 90% efficiency. • Biodiesel derived from SCO of R. glutinis R4 satisfied international fuel standards. In the context of the global energy crisis and the constant demand for biofuels, this work explored the biodiesel production from single-cell oils (SCO) produced by the Antarctic oleaginous yeast Rhodotorula glutinis R4 from low-cost local agro-industrial by-products (sugarcane molasses and waste glycerol). The lipid accumulation reached 46.8% and 40.7% at 120 h of culture using glycerol and molasses, respectively, which correspond to 5.72 and 8.68 g L -1 of final lipid concentration. R. glutinis R4 yielded 0.172 and 0.185 gram of lipids per gram of substrate consumed grown in molasses or glycerol medium, respectively. These amounts being higher than the ones obtained in glucose medium (0.126 g g -1 ). At 120 h of culture, lipid volumetric productivities were 0.048 and 0.072 g L −1 h −1 using glycerol and molasses, respectively, and 0.043 g L −1 h −1 in the glucose yeast extract (GYM) medium. Oleic acid is the predominant fatty acid in the oils from R. glutinis R4, reaching 67.5% with molasses, thus indicating that it is adequate for biodiesel synthesis. This is the first study where SCO produced by R. glutinis R4 were converted into biodiesel by acid transesterification with an efficiency above 90%. The biodiesel produced by R. glutinis R4 grown on culture media containing molasses or waste glycerol is fully compliant with the international standards for biodiesel. SCO obtained from R. glutinis R4 using molasses and waste-glycerol can be effectively used as sources of triacylglycerols for biodiesel production.

Multi-omics profiling reveals potential mechanisms of culture temperature modulating biosynthesis of carotenoids, lipids, and exopolysaccharides in oleaginous red yeast Rhodotorula glutinis ZHK

Rhodotorula glutinis is a biotechnologically important oleaginous red yeast that has piqued interest as a promising platform strain to industrially synthesize numerous valuable compounds such as carotenoids, lipids, and exopolysaccharides. Here, the effects of low and high culture temperatures on carotenoids, lipids, and exopolysaccharides production in R. glutinis ZHK were investigated. The results indicated that low temperature (16 °C) significantly increased crude exopolysaccharides production, while high temperature (32 °C) significantly increased certain carotenoids (torulene and torularhodin) and total lipids production as compared to control (25 °C) after 5 days of cultivation. Multi-omics analysis suggested that low temperature promotes exopolysaccharide synthesis probably because more exopolysaccharide precursors are made when the expression levels of related protein-encoding genes and activities of their encoded enzymes in the TCA cycle pathway are reduced. Furthermore, high temperature enhances the yield of torulene, torularhodin, and total lipids might be attributed to the increased production of acetyl-CoA derived from the up-regulation of the TCA cycle pathway, as well as the up-regulation of related pathways directly related to carotenogenesis and lipogenesis. This work should uncover a feasible fermentation process for improving carotenoids, lipids, and exopolysaccharides production in R. glutinis ZHK, and provide molecular foundation to further improve their yield by genetic engineering.

The Tannase from red yeast Rhodotorula glutinis: purification and characterization

The tannase enzyme was successfully purified to homogeneity from the culture broth of red yeast strain Rhodotorula glutinis DB2 in a three-tandem step involving ultrafiltration (5 kDa and 100 kDa systems), Sephadex G-200 gel filtration chromatography, and DEAE Sepharose CL-4B anion exchange chromatography. The purified tannase appeared to be homogeneous on sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE). The purified tannase had a specific activity of 3.33 U mg−1, with a 1.3% recovery and overall purification of 302-fold. The molecular mass of the tannase estimated by SDS-PAGE was about 73 kDa. The tannase had an optimum pH of 6.0 and an optimum temperature of 40 °C. The most stable pH was 7.0, and the enzyme was stable up to 40 °C. One mmol L−1 of Fe3+, Sr2+, Na+, and Pb2+ were found to promote tannase activity, whilst 1.0 mmol L−1 of Ba2+, Ca2+, Mg2+, Zn2+, Hg+, Ag+, Co2+, Fe2+, Mn2+, Cu2+, Cd2+, Al3+, K+, Ni2+, and Li+ inhibited tannase activity.

Selective recovery and purification of carotenoids and fatty acids from Rhodotorula glutinis using mixtures of biosolvents

Selective recovery and purification of carotenoids and lipids from oleaginous red yeast Rhodotorula glutinis require a complex integration of different downstream operations. Envisioning a future industrial application in the bioeconomy framework, an experimental planning was used to design ternary mixtures of bio-based solvents (biosolvents) for simultaneous recovery and selective separation of carotenoids (i.e., β-carotene and torularhodin) and fatty acids (i.e., margaric acid, stearic acid and pentadecylic acid) from untreated (fresh wet) and freeze/thaw pre-treated (wet and dry) biomass of Rhodotorula glutinis CCT-2186. Two ternary systems of biosolvents, (i) ethanol:ethyl lactate:water and ii) ethanol:ethyl acetate:water, were investigated in solid–liquid extraction procedures to permeabilize/disintegrate the yeast cells and to enhance the selective recovery of β-carotene, torularhodin and fatty acids from the intracellular environment. Optimization of the ternary mixture composition for recovery of carotenoids and fatty acids from the three types of biomass allowed to obtain yields higher than 75% (w/w) from pre-treated dry biomass using mixture of ethanol:ethyl acetate:water (67:33:00% w/w/w). The best systems were then integrated with a liquid–liquid extraction for the selective separation of carotenoids and fatty acids and solvent recycling. The mixtures of biosolvents were reused up to three consecutive extraction cycles, maintaining high extraction efficiency yields of both carotenoids (>45% w/w) and lipids (>30% w/w). At the end, the biological activity of the carotenoids extracts was confirmed by determining the antioxidant activity using Electron Paramagnetic Resonance (EPR) and the stable free radical 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH·). The highest antioxidant activity (93%) was obtained with torularhodin (250 μg/mL). This study confirms that extraction platforms using mixed biosolvents are simple, efficient and sustainable solutions for the selective recovery and separation of carotenoids and fatty acids from microbial biomass.

Effect of Polysorbates on the Growth of Rhodotorula Glutinis in Oil Rich Medium

Abstract The present study has investigated the effect of oil rich medium supplementation with polysorbates Tween 20, 40 and 80, for the cultivation of red oleaginous yeast Rhodotorula glutinis. R. glutinis has been cultivated in yeast extract peptone glucose modified broth (mYPG) supplemented with 2 % of waste cooking rapeseed oil and three polysorbate types with 0.5 %, 1 %, 2%, 3 %, 4 %, 5 %, 6 %, 7 %, 8 %, 9 % and 10 % concentration each. Yeast biomass was measured by the thermogravimetric method at 105 °C each day during 7-day experiment. The oil rich medium supplementation with Tween 20, 40 and 80 at concentrations ranging from 2 % to 10 % significantly increased the biomass of R. glutinis. All three types of the studied polysorbates with 0.5 % and 1 % concentration, did not affect yeast growth and the dry biomass – results were similar to the control sample without polysorbate addition. Between the three types of polysorbates, Tween 20 was selected as the preferable for R. glutinis cultivation with an optimal concentration of 2 %. Cultivation of R. glutinis in oil rich medium with polysorbates Tween 20, 40 and 80, supplementation up to 10 % concentration did not have had an inhibitory effect on the biomass growth.

Genomics and lipidomics analysis of the biotechnologically important oleaginous red yeast Rhodotorula glutinis ZHK provides new insights into its lipid and carotenoid metabolism

BackgroundRhodotorula glutinis is recognized as a biotechnologically important oleaginous red yeast, which synthesizes numerous meritorious compounds with wide industrial usages. One of the most notable properties of R. glutinis is the formation of intracellular lipid droplets full of carotenoids. However, the basic genomic features that underlie the biosynthesis of these valuable compounds in R. glutinis have not been fully documented. To reveal the biotechnological potential of R. glutinis, the genomics and lipidomics analysis was performed through the Next-Generation Sequencing and HPLC-MS-based metabolomics technologies.ResultsHere, we firstly assemble the genome of R. glutinis ZHK into 21.8 Mb, containing 30 scaffolds and 6774 predicted genes with a N50 length of 14, 66,672 bp and GC content of 67.8%. Genome completeness assessment (BUSCO alignment: 95.3%) indicated the genome assembly with a high-quality features. According to the functional annotation of the genome, we predicted several key genes involved in lipids and carotenoids metabolism as well as certain industrial enzymes biosynthesis. Comparative genomics results suggested that most of orthologous genes have underwent the strong purifying selection within the five Rhodotorula species, especially genes responsible for carotenoids biosynthesis. Furthermore, a total of 982 lipids were identified using the lipidomics approaches, mainly including triacylglycerols, diacylglyceryltrimethylhomo-ser and phosphatidylethanolamine.ConclusionUsing whole genome shotgun sequencing, we comprehensively analyzed the genome of R. glutinis and predicted several key genes involved in lipids and carotenoids metabolism. By performing comparative genomic analysis, we show that most of the ortholog genes have undergone strong purifying selection within the five Rhodotorula species. Furthermore, we identified 982 lipid species using lipidomic approaches. These results provided valuable resources to further advance biotechnological applications of R .glutinis.

Effect of exogenous stress factors on the biosynthesis of carotenoids and lipids by Rhodotorula yeast strains in media containing agro-industrial waste

In this study, we aimed to determine the effect of exogenous stress factors (sodium chloride as osmotic stressor, hydrogen peroxide as an inducer of oxidative stress, white light irradiation, and low temperature) on the biosynthesis of carotenoids and lipids by red yeast (Rhodotorula glutinis, R. mucilaginosa, and R. gracilis) during cultivation in media containing potato wastewater and glycerol. According to our results, the yeast were able to grow and biosynthesize lipids and carotenoids in the presence of the applied stress factors. Low temperature caused an increase in the biosynthesis of intracellular lipids and carotenoids. R. gracilis synthesized lipids (21.1 g/100 gd.w.) and carotenoids (360.4 µg/gd.w.) in greater quantities than that of other strains. Under these conditions, there was also an increase in the content of unsaturated fatty acids, especially linoleic and linolenic acids. The highest percentage of polyunsaturated fatty acid (PUFA) (30.4%) was synthesized by the R. gracilis yeast after cultivation at 20°C. Their quantity was 2.5-fold greater than that of the biomass grown in control conditions. The contribution of individual carotenoid fractions depended both on the yeast strain and the culture conditions. Induction of osmotic stress and low temperature intensified the biosynthesis of β-carotene (up to 73.9% of the total carotenoid content). In oxidative stress conditions, yeast synthesized torulene (up to 82.2%) more efficiently than under other conditions, whereas white light irradiation increased the production of torularhodin (up to 20.0%).

Engineering the oleaginous red yeast Rhodotorula glutinis for simultaneous \u03b2-carotene and cellulase production

Rhodotorula glutinis, an oleaginous red yeast, intrinsically produces several bio-products (i.e., lipids, carotenoids and enzymes) and is regarded as a potential host for biorefinery. In view of the limited available genetic engineering tools for this yeast, we have developed a useful genetic transformation method and transformed the β-carotene biosynthesis genes (crtI, crtE, crtYB and tHMG1) and cellulase genes (CBHI, CBHII, EgI, EgIII, EglA and BGS) into R. glutinis genome. The transformant P4-10-9-63Y-14B produced significantly higher β-carotene (27.13 ± 0.66 mg/g) than the wild type and also exhibited cellulase activity. Furthermore, the lipid production and salt tolerance ability of the transformants were unaffected. This is the first study to engineer the R. glutinis for simultaneous β-carotene and cellulase production. As R. glutinis can grow in sea water and can be engineered to utilize the cheaper substrates (i.e. biomass) for the production of biofuels or valuable compounds, it is a promising host for biorefinery.

The Effect of Zn(II) Ions and Reactive Oxygen on the Uptake of Zinc and Production of Carotenoids by Selected Red Yeasts.

Three strains of red yeast Rhodosporidium kratochvilovae, Rhodotorula glutinis and Sporidiobolus salmonicolor were studied for their responses to the presence metal stress, oxidative stress and a combination of these stress factors. For all yeast strains, the production of β-carotene increased in stress conditions. The combination of H2 O2 and Zn2+ significantly activated the pathways for the production of torularhodin in the strain R.glutinis (from 250 to 470μgg-1 DCW) as well as β-carotene (from 360 to 1100μgg-1 DCW) and torulene (from 100 to 360μgg-1 DCW) in Sp.salmonicolor. Strains of R.glutinis and Rh.kratochvilovae bound the majority of Zn(II) ions to the fibrillar part of the cell walls, whereas the strain Sp.salmonicolor bound them to both extracellular polymers and the fibrillar part of the cell walls. A decrease in the ability of yeasts to tolerate higher concentrations of Zn(II) in the presence of free radicals (hydrogen peroxide) was also found.

Enhanced single cell oil production by mixed culture of Chlorella pyrenoidosa and Rhodotorula glutinis using cassava bagasse hydrolysate as carbon source

The single cell oil (SCO) production by the mono and mixed culture of microalgae Chlorella pyrenoidosa and red yeast Rhodotorula glutinis was investigated using non-detoxified cassava bagasse hydrolysate (CBH) as carbon source. The results suggested that the two strains were able to tolerate and even degrade some byproducts presented in the CBH, and the mixed culture approach enhanced the degradation of certain byproducts. Biomass (20.37 ± 0.38 g/L) and lipid yield (10.42 ± 1.21 g/L) of the mixed culture achieved in the batch culture were significantly higher than that of the mono-cultures (p < 0.05). The fed-batch culture further raised the biomass and lipid yield to 31.45 ± 4.93 g/L and 18.47 ± 3.25 g/L, respectively. The lipids mainly composed of oleic acid and palmitic acid, suggesting the potential applications such as biofuel feedstock, cosmetics, food additives and lubricant. This study provided new insights for the integration of the economical SCO production with agro-industrial waste disposal.

Kinetic study of growth, lipid and carotenoid formation in β-carotene producing Rhodotorula glutinis

The oleaginous and red yeast Rhodotorula glutinis CCY 20-2-26 is known for its high-storage lipids accumulation in cells as well as for β-carotene biosynthesis. The work is focused on the study of lipogenesis and carotenoid pigments formation by the yeast grown in media with four different C/N ratios (20:1, 50:1, 70:1 and 100:1). Total fatty acids accumulation in cells reached the maximal value of 48% and yielded up to 8.9 g fatty acid/L media under C/N 70:1. On contrary, while the highest pigment accumulation in the yeast (1268 μg/g of cells) was found at the C/N ratio of 20:1, the maximal carotenoid yield (mainly β-carotene) of 12.7 mg/L was obtained under 50:1 ratio. Calculation of kinetic parameters of metabolites production revealed the metabolic correlations among glucose consumption, lipogenesis and carotenoid biosynthesis. It was demonstrated that glucose exhaustion resulted in reduction of growth and lipid accumulation in cells. Then, storage fatty acids, especially palmitic and oleic acids, begun to be degraded by β-oxidations and formed acetyl-CoA which was especially used for biosynthesis of β-carotene. This is the first study providing the new hypothesis about the metabolic connection between fatty acids and β-carotene metabolism in the red yeasts.

Correlation between lipid and carotenoid synthesis in torularhodin-producing Rhodotorula glutinis

The oleaginous red yeast Rhodotorula glutinis produces carotenoid pigments, especially torularhodin and β-carotene, in significant amounts. We have analyzed in detail carotenoid and lipid biosynthesis in a torularhodin-producing strain of R. glutinis cultivated at different carbon:nitrogen (C/N) ratios (20:1, 50:1, 70:1, and 100:1). When the strain was cultivated in media with low C/N ratios (20:1 and 50:1), glucose was completely utilized and carotenoid formation was stimulated. Maximum pigment production reached 12.9 mg/L of medium and 2.3 mg/g of biomass at the C/N ratio of 20:1. It was noted that β-carotene synthesis was prominent when glucose was present in the medium. However, glucose exhaustion in the media at C/N ratios of 20:1 and 50:1 was closely accompanied by the predominant formation of torularhodin. The growth of R. glutinis in media with C/N ratios of 70:1 and 100:1 favored lipid accumulation in the cells but carotenoid biosynthesis was reduced. In addition, glucose consumption was linked to a rapid decrease in oleic acid levels in the total intracellular lipids. The kinetic analysis clearly indicated a correlation between oleic acid levels in total lipids and torularhodin accumulation in the cells. The results may suggest that acetyl-CoA formed from oleic acid degradation is metabolized through the mevalonate/isoprenoid/carotenoid pathways directly to torularhodin.

Hydrolysis treatments of fruit and vegetable waste for production of biofuel precursors

This study investigated hydrolysis approaches for cultivation of the oleaginous red yeast Rhodotorula glutinis for biodiesel production, whilst utilising the residual solids (RS) for biogas production. Macerated fruit and vegetable waste (FVW) (24h–4°C-leachate served as the control, Pcon) was hydrolysed chemically (Chem), thermally (Therm) and using a combined thermo-chemical treatment (T-Chem). All cleared hydrolysates supported growth of R. glutinis, which was nitrogen-limited. T-Chem hydrolysates yielded highest biomass, total fatty acids (TotFA) and RS-derived biogas yields, biomass TotFA failed to meet standards for fuel density and higher heating values, met by the other treatments. Even though Pcon-derived yields were slightly lower, it is recommended for FVW treatment for local biogas and biodiesel production due to energy and environmental impact considerations.

Study of Rhodotorula glutinis growth and lipid production using low cost substrates

The present day challenge for biodiesel production is that as feedstock varied vegetable oils such as soybean oils, rap seed oils, palm oils and waste cooking oils are being used making it uneconomical. Microbial oil could represent an alternative to produce bio-oils for biodiesel production. In the present study in our lab red oleaginous yeast Rhodotorula glutinis was used for lipid production using various low cost substrates as sole carbon source. Rhodotorula glutinis culture was obtained from NCIM Pune and was subcultured and maintained on YPD medium. The growth conditions were optimised and dry cell weight and lipid content were estimated using fruit ,peel and sugar cane residue hydrolysate. The study can be further extended using different other substrates and result in cost effective high density cell culture.

Lipid Production for Microbial Biodiesel by the Oleagenious Yeast Rhodotorula glutinis Using Hydrolysates of Wheat Straw and Miscanthus as Carbon Sources

This study investigated the lipid production potential of the red-yeast Rhodotorula glutinis grown on non-detoxified hydrolysates from wheat straw and Miscanthus. The experiments were carried out as batch fermentation experiments in a five liter fermenter. Generally, wheat straw was found to provide a higher sugar content (24.2 g L−1) compared to Miscanthus (20.7 g L−1) which resulted in a higher lipid production. When wheat straw hydrolysate was used as a carbon source, cell mass and lipid production showed a significant increase in maximum cell mass and lipid yield of 11.8 and 1.4 g L−1, respectively. Maximum cell mass growth of R. glutinis on Miscanthus hydrolysate as a carbon source fell within the same range (11.8 g L−1), whereas maximum lipid production after 96 h was lower (0.93 g L−1). A major limitation for cell growth and lipid production was the rapid exhaustion of the total sugar content after 96 h of fermentation in both hydrolysates. This resulted in a decelerated cell growth and lipid production. Lipids from both hydrolysates were dominated by long chain fatty acids, in particular C 16:0, C 18:1 and C 18:2. This composition of lipids corresponds to the common fatty acid obtained from oleaginous microorganisms and indicates a good level of suitability for biodiesel production.

Effect of different C/N ratios on carotenoid and lipid production by Rhodotorula glutinis

Due to the increasing demand for sustainable biofuels, microbial oils as feedstock for the transesterification into biodiesel have gained scientific and commercial interest. Also, microbial carotenoids have a considerable market potential as natural colorants. The carbon to nitrogen (C/N) ratio of the respective cultivation media is one of the most important parameters that influence the production of microbial lipids and carotenoids. Thus, in the present experiment, the influence of different C/N ratios, initial glucose loadings, and ammonium concentrations of the cultivation medium on microbial cell growth and lipid and carotenoid production by the oleaginous red yeast Rhodotorula glutinis has been assessed. As a general trend, both lipid and carotenoid production increased at high C/N ratios. It was shown that not only the final C/N ratio but also the respectively applied initial carbon and nitrogen contents influenced the observed parameters. The lipid yield was not affected by different ammonium contents, while the carotenoid production significantly decreased both at low and high levels of ammonium supply. A glucose-based increase from C/N 70 to 120 did not lead to an increased lipid production, while carotenoid synthesis was positively affected. Generally, it can be asserted that lipid and carotenoid synthesis are stimulated at higher C/N ratios.

Lipid and carotenoid production by oleaginous red yeast Rhodotorula glutinis cultivated on brewery effluents

This study investigated the production of microbial lipids for biodiesel production and high-value carotenoids by Rhodotorula glutinis combined with the use of brewery wastewater as carbon source for three treatments: (raw wastewater) WWraw, (glucose supplemented raw wastewater) WWglu and a (synthetic sugar medium) WWsynth. The collected brewery effluents showed high contents of sugars (maltose 24.34 g L−1; glucose 5.77 g L−1), but the low utilization of maltose led to a limitation of carbon in WWraw and WWglu. Since nitrogen was still available, carbon was channeled into cell growth instead of lipid formation, reaching an overall biomass production of 5.22 g L−1, 7.38 g L−1, and 9.55 g L−1, respectively. Carotenoids were synthesized in all treatments with total average carotenoid contents between 0.6 and 1.2 mg L−1 and with high proportions of β-carotene (∼50%) in the wastewater treatments. Suboptimal culture conditions (pH; aeration) have been identified as obstacles for higher lipid and carotenoid yields. Nevertheless, brewery wastewaters can be considered as carbon source for microbial fermentation, since they can be assumed to be an adequate source of nitrogen and other nutrients, whereas the utilization of maltose needs to be increased to achieve considerable amounts of lipid and carotenoid production.