Search Results (15)

Carotenoids are widely recognized for their antioxidant and health-beneficial properties, making them attractive for applications in the food, pharmaceutical, medical, and agricultural sectors. Rhodotorula yeasts are considered one of the most suitable alternatives for carotenoid synthesis due to their rapid biomass growth and high pigment yield. During this study, based on the sequences of the ITS region between 18S and 28S rRNA genes, the yeast strains were identified as belonging to Rhodotorula babjevae, R. dairenensis, R. diobovata, R. glutinis, R. graminis, R. ingeniosa, R. kratochvilovae, and R. mucilaginosa. The production of carotenoids by different Rhodotorula yeast strains was analyzed under the combined effects of lighting and temperature. Among all tested strains, the isolate identified as R. ingeniosa exhibited the lowest carotenoid content, ranging from 0.18 to 0.23 mg/g biomass. The highest levels of pigment were accumulated in dark conditions by R. babjevae (0.86 mg/g biomass) and R. graminis (0.76 mg/g biomass) cultivated for 14 days at a constant temperature of 26 °C, and by R. glutinis (0.89 mg/g biomass) after incubation at 4 °C. The majority of yeasts tested produced more carotenoids at a higher temperature. It was observed that in R. babjevae, R. glutinis, and R. graminis, lighting negatively affected the pigment content regardless of incubation temperature. In these strains, the pigment content decreased by 1.2- to 1.4-fold after one week of cultivation under light conditions at 26 °C, compared to cultures grown in the dark. The results suggest that the isolated Rhodotorula strains could be attractive candidates for the efficient synthesis of carotenoids. Full article

In this study, a comparative approach was used with the aim of filling the knowledge gap regarding the productive and economic parameters of two native B. mori silkworm breeds (Lines C and Z) fed with different diets, namely mulberry leaves alone and mulberry leaves with R. glutinis yeast at two different concentrations (1 × 10⁹ and 1 × 10⁷ CFU/mL). The trifactorial experiment was carried out with 600 silkworms during the fifth instar, with 300 for each breed and 50 larvae per rearing tray. The larvae were randomly assigned into three feeding groups, with two replicates: in the control group (C), the larvae received ordinary mulberry leaves; in the first experimental group (RG-1), the larvae were given mulberry leaves supplemented with R. glutinis yeast at a 1 × 10⁷ concentration; and in the second experimental group (RG-2), the larvae received the same quantity of mulberry leaves as the C and RG-1 groups, but with R. glutinis yeast at a 1 × 10⁹ concentration. Line C larvae in the RG-1 group revealed higher values for most of the productive traits assessed. There was a positive and significant correlation between the weights and lengths of the larvae and the silk gland, the silk gland and the shell, the cocoon and the pupae and the shell, and the shell and the pupa size (p < 0.001). The steady decline in the parameters at a higher concentration suggests that R. glutinis positively influences a number of silkworm growth features at a recommended dosage of 1 × 10⁷; however, further research is required to more precisely identify the mechanisms involved. Full article

Seed productivity and quality are the bases of modern agriculture. To determine the optimal conditions in terms of seed production and quality, the effect of foliar plant biostimulant treatments (at the beginning and in the middle of the peduncle formation phase and at the beginning of flowering) based on amino acids (Multimolig M and Aminosil), silicon (Si) (Siliplant), selenium (nano-Se), a Rhodotorula glutinis soil yeast formulation, and a fertilizer (Wuxal Macromix), plus an untreated control (only water-sprayed plants), were assessed on Beta vulgaris seed plants grown in an open field in the Moscow region in 2022–2023. Silicon and nano-Se foliar supply led to the highest seed production and viability, as well as positively affecting the yield and quality of the microgreens produced from the latter seeds. Despite the stability of the size distribution of small- and large-sized seeds, only the application of Si increased the occurrence of the large-sized seed class by up to 53%, while R. glutinis fostered a homogenous distribution of seeds among the different diameter classes. The application of all of the biostimulants, except R. glutinis, provided a decrease in oxidative stress in the seeds (reflected in a significant reduction in proline levels), especially for the small-sized seed class, with the highest beneficial effects being caused by Aminosil and Siliplant. All of the treatments were beneficial in terms of chlorophyll and betalain pigment accumulation but did not significantly affect the microgreens’ antioxidant status. The beneficial effect of the biostimulants revealed provides the basis for beetroot seed production and quality improvements to meet the requirements of the Sustainable Development Goals of the United Nations aiming to fight hunger and improve human health and well-being. Full article

This study evaluated the biocontrol effect of isolated epiphytic yeasts (Papiliotrema terrestris, Hanseniaspora uvarum, and Rhodosporidium glutinis) against Botrytis cinerea and Alternaria alternata in blueberry fruits and its possible mechanisms. Our findings indicated that the three tested yeasts exerted a good biocontrol effect on postharvest diseases in blueberry, and that H. uvarum was the most effective. In addition, the three tested yeasts could improve the postharvest storage quality of blueberry fruits to some extent. H. uvarum demonstrated the strongest direct inhibitory effect on pathogens by suppressing spore germination, mycelial growth, and antifungal volatile organic compound (VOC) production. P. terrestris showed the highest extracellular lytic enzymes activities. It also had better adaptation to low temperature in fruit wounds at 4 °C. The biofilm formation capacity was suggested to be the main action mechanism of R. glutinis, which rapidly colonized fruit wounds at 20 °C. Several action mechanisms are employed by the superb biocontrol yeasts, while yeast strains possess distinctive characteristics and have substantially different action mechanisms. Full article

Single-cell oils (SCOs) offer a promising alternative to conventional biodiesel feedstocks. The main objective of this work was to obtain SCOs suitable for biodiesel production from the oleaginous yeast Rhodotorula glutinis R4 using sugarcane vinasse from a local sugar-derived alcohol industry as the substrate. Additionally, crude glycerol from the local biodiesel industry was evaluated as a low-cost carbon source to replace expensive glucose and as a strategy for integrating the bioethanol and biodiesel industries for the valorization of both agro-industrial wastes. R4 achieved a high lipid accumulation of 88% and 60% (w/w) in vinasse-based culture media, containing 10% and 25% vinasse with glucose (40 g L⁻¹), respectively. When glucose was replaced with crude glycerol, R4 showed remarkable lipid accumulation (40%) and growth (12.58 g L⁻¹). The fatty acids profile of SCOs showed a prevalence of oleic acid (C18:1), making them suitable for biodiesel synthesis. Biodiesel derived from R4 oils exhibits favorable characteristics, including a high cetane number (CN = 55) and high oxidative stability (OS = 13 h), meeting international biodiesel standards (ASTMD6751 and EN14214) and ensuring its compatibility with diesel engines. R. glutinis R4 produces SCOs from vinasse and crude glycerol, contributing to the circular economy for sustainable biodiesel production. Full article

Sugar-rich waste streams, generated in very high quantities worldwide, constitute an important source of environmental pollution. Their eco-friendly conversions into a plethora of added-value compounds through the use of microbial fermentations is currently a very “hot” scientific topic. The aim of this study, was to assess the potential of single cell oil (SCO), microbial mass and citric acid (CA) production by non-conventional yeast strains growing on expired (“waste”) glucose. Six yeast strains (viz. Rhodosporidium toruloides DSM 4444, Rhodotorula glutinis NRRL YB-252, R. toruloides NRRL Y-27012, Yarrowia lipolytica LFMB Y-20, Y. lipolytica ACA-DC 50109 and Lipomyces starkeyi DSM 70296) were initially grown in shake flasks with expired glucose used as substrate under nitrogen limitation, in order to “boost” the cellular metabolism towards the synthesis of SCO and CA, and their growth response was quantitatively evaluated. Initial glucose concentration (Glc₀) was adjusted at c. 50 g/L. Besides Y. lipolytica, all other yeast strains produced noticeable SCO quantities [lipid in dry cell weight (DCW) ranging from 25.3% w/w to 55.1% w/w]. Lipids of all yeasts contained significant quantities of oleic acid, being perfect candidates for the synthesis of 2nd generation biodiesel. The highest DCW production (=13.6 g/L) was obtained by L. starkeyi DSM 70296, while both Y. lipolytica strains did not accumulate noticeable lipid quantities, but produced non-negligible CA amounts. The most promising CA-producing strain, namely Y. lipolytica ACA-DC 50109 was further studied in stirred-tank bioreactor systems, while the very promising DCW- and SCO-producing L. starkeyi DSM 70296 was further studied in shake flasks. Both strains were grown on media presenting higher Glc₀ concentrations and the same initial nitrogen quantity as previously. Indeed, L. starkeyi grown at Glc₀ = 85 g/L, produced DCW_max = 34.0 g/L, that contained lipid =34.1% w/w (thus SCO was =11.6 g/L). The strain ACA-DC 50109 in stirred tank bioreactor with Glc₀ ≈ 105 g/L produced CA up to 46 g/L (yield of CA produced on glucose consumed; Y_CA/Glc ≈ 0.45 g/g). Finally, in fed-batch bioreactor experiment, the significant CA quantity of 82.0 g/L (Y_CA/Glc = 0.50 g/g) was recorded. Concluding, “waste” glucose proved to be a suitable substrate for a number of non-conventional yeast strains. Y. lipolytica ACA-DC 50109 produced significant quantities of CA while L. starkeyi DSM 70296 was a very interesting DCW- and SCO-producing candidate. These strains can be used as potential cell factories amenable to convert glucose-based residues into the mentioned metabolic compounds, that present high importance for food, chemical and biofuel facilities. Full article

Carotenoids are fat-soluble bioactive compounds found in plants, animals, and microorganisms, which have a range of health benefits and great technological and industrial importance in the fields of pharmaceuticals, food, and biotechnology. Yeasts of the genus Rhodotorula can biosynthesize large amounts of carotenoids under environmental stress conditions, and this process may become industrially feasible if production costs are minimized using low-cost by-products as nutrient sources. As cassava roots are produced and consumed in large quantities in the Amazon biome, our research aimed to investigate the best cultivation conditions in a benchtop bioreactor for the biotechnological production of carotenoids by R. glutinis using manipueira as a low-cost substrate. Manipueira is wastewater generated during cassava flour production, and it was concentrated at 12 °Brix for this study. In addition, the carotenoid composition, at the best cultivation condition, was analyzed by LC-MS. Higher carotenoid contents (1410 μg/g of dried biomass) than described in the literature, and biomass (10 g), were produced by R. glutinis using concentrated manipueira as a low-cost substrate after cultivation at pH 5, 35 °C and agitation at 150 rpm. At the best cultivation conditions, β-carotene, lutein, and 5,8-epoxy-lutein were the major carotenoids, with the latter two compounds being identified for the first time in the biomass of R. glutinis. Therefore, concentrated manipueira can be seen as a feasible alternative and low-cost substrate to be used for the biotechnological production of high carotenoid contents by R. glutinis. Full article

Compared to agrochemicals, bioinoculants based on plant microbiomes are a sustainable option for increasing crop yields and soil fertility. From the Mexican maize landrace “Raza cónico” (red and blue varieties), we identified yeasts and evaluated in vitro their ability to promote plant growth. Auxin production was detected from yeast isolates and confirmed using Arabidopsis thaliana plants. Inoculation tests were performed on maize, and morphological parameters were measured. Eighty-seven yeast strains were obtained (50 from blue corn and 37 from red corn). These were associated with three families of Ascomycota (Dothideaceae, Debaryomycetaceae, and Metschnikowiaceae) and five families of Basidiomycota (Sporidiobolaceae, Filobasidiaceae, Piskurozymaceae, Tremellaceae, and Rhynchogastremataceae), and, in turn, distributed in 10 genera (Clavispora, Rhodotorula, Papiliotrema, Candida, Suhomyces, Soliccocozyma, Saitozyma Holtermaniella, Naganishia, and Aeurobasidium). We identified strains that solubilized phosphate and produced siderophores, proteases, pectinases, and cellulases but did not produce amylases. Solicoccozyma sp. RY31, C. lusitaniae Y11, R. glutinis Y23, and Naganishia sp. Y52 produced auxins from L-Trp (11.9–52 µg/mL) and root exudates (1.3–22.5 µg/mL). Furthermore, they stimulated the root development of A. thaliana. Inoculation of auxin-producing yeasts caused a 1.5-fold increase in maize plant height, fresh weight, and root length compared to uninoculated controls. Overall, maize landraces harbor plant growth-promoting yeasts and have the potential for use as agricultural biofertilizers. Full article

Whey edible films (EFs) functionalized with essential oils have a high potential to be used on various foods due to their antimicrobial and antioxidant activities. Encapsulation is applied for a better retention of volatiles in EFs; however, the functional properties of EFs are modified. The properties of EFs containing thyme essential oil (TEO) encapsulated by co-precipitation in β-CD, developed in three formulae, with inclusion complexes (EF/IC1, EF/IC2, and EF/IC3, respectively) in 15:85, 26:74, and 35:65 mass ratios were studied. Thymol is the main volatile in the ICs with TEO/β-CD (50%–60% of the total volatiles). In comparison with EF/TEO, all three formulae with EF/ICs had better, but similar, WVPs (p > 0.05). The EF/IC2 displayed a different FTIR profile than EF/IC1 and EF/IC3, suggesting a smaller number of free functional groups. The EF/IC2 showed better transparency in comparison with EF/IC1 and EF/IC3. All EF/ICs moderately inhibited R. glutinis, with the strongest activity registered by EF/IC3 (p < 0.05), but did not inhibit G. candidum, while showing a strong antibacterial activity against B. cereus. All EF/ICs inhibited 65%–70% of the total free radicals. The EF/ICs ensured a gradual release of VOCs in food simulants, with a higher rate in 95% ethanol than in water. These results have demonstrated the properties of EF/ICs with TEO/β-CD as bioactive packaging systems for foods. Full article

Local fruit cultivars may improve the originality of specialty beers both directly, by conferring peculiar tastes and flavors, and indirectly, as a reservoir of new starter strains. Accordingly, the fungal and bacterial communities of Bisucciu fruit, a Sardinian apricot cultivar used to produce a local fruit beer, were here investigated by culture-dependent methods. From the 16S rDNA and ITS sequence analyses of 68 epiphytic isolates, 5 bacterial species and 19 fungal species were identified. Aureobasidium pullulans and Rhodotorula glutinis were the dominant fungal species, while Enterococcus mundtii (Firmicutes) and Frigoribacterium faeni (Actinobacteria) were the most represented species among bacterial isolates. Enrichment cultures of fresh apricot puree, followed by fermentation trials in beer wort and beer wort added with apricot puree, allowed the selection of four isolates of Pichia kudriavzevii, Hanseniaspora uvarum, H. pseudoguilliermondii, and H. clermontiae able to dominate over the Bisucciu native microbiota and to produce from 0.57% to 0.74% (vol/vol) of ethanol. HS-SPME-GC/MS analysis highlighted a significant increase in the ester and alcohol fractions as well as a reduction in terpenes after fermentation with the selected yeasts. Results obtained suggest that the yeast isolates may contribute to the definition of the taste and flavor of beers when used in mixed fermentations with Saccharomyces. Full article

Triangularia mangenotti was analyzed for the production of secondary metabolites, resulting in the isolation of known zopfinol (1) and its new derivatives zopfinol B–C (2–4), the 10-membered lactones 7-O-acetylmultiplolide A (5) and 8-O-acetylmultiplolide A (6), together with sordarin (7), sordarin B (8), and hypoxysordarin (9). The absolute configuration of 1 was elucidated by the synthesis of MPTA-esters. Compound 1 showed antimicrobial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus and the fungus Mucor hiemalis. While 4 was weakly antibacterial, 3 showed stronger antibiotic activity against the Gram-positive bacteria and weak antifungal activity against M. hiemalis and Rhodotorula glutinis. We furthermore observed the cytotoxicity of 1, 3 and 4 against the mammalian cell lines KB3.1 and L929. Moreover, the new genus Pseudorhypophila is introduced herein to accommodate Triangularia mangenotii together with several species of Zopfiella—Z. marina, Z. pilifera, and Z. submersa. These taxa formed a well-supported monophyletic clade in the recently introduced family Navicularisporaceae, located far from the type species of the respective original genera, in a phylogram based on the combined dataset sequences of the internal transcribed spacer region (ITS), the nuclear rDNA large subunit (LSU), and fragments of the ribosomal polymerase II subunit 2 (rpb2) and β-tubulin (tub2) genes. Zopfiella submersa is synonymized with P. marina due to the phylogenetic and morphological similarity. The isolation of zopfinols 1–4 and sordarins 7–9 confirms the potential of this fungal order as producers of bioactive compounds and suggests these compounds as potential chemotaxonomic markers. Full article

The coproduction of lipid and carotenoid by red yeasts in one cycle is more convenient and economical for the industrial sectors, while the kinetics correlation between both products under different culture conditions has been scarcely studied. This study is aiming to correlate the impact of different carbon sources, carbon to phosphorus ratio (C/P), temperature, aeration, pH, and metals on dry cell weight, lipid (GC and fluorescence microscope), and carotenoid (HPLC) production by Rhodotorula glutinis, and applying a novel feeding approach using a 5 L bioreactor to enhance carotenoid and unsaturated fatty acid production by R. glutinis. Whatever the culture condition is, the reversible correlation between lipid and carotenoid production was detected. Remarkably, when adding 0.1 mM BaCl₂, cellular lipid was significantly increased 14% more than the control, with 79.3% unsaturated fatty acid (46% C18:2 and C18:3) and 50% γ-carotene, while adding 1 mM NiSO₄, cellular carotenoid was enhanced around 53% than the control (torulene 88%) with 81% unsaturated fatty acid (61% oleic acid). Excitingly, 68.8 g/l biomass with 41% cellular lipid (79% unsaturated fatty acid) and 426 µg_pigment/g_dcw cellular carotenoid (29.3 mg/L) (71% torulene) were obtained, when the pH-temperature dual controlled process combined with metallo-sulfo-phospho-glucose feeding approach in the 5 L bioreactor during the accumulation phase was conducted. This is the first study on the kinetic correlation between lipid and carotenoid under different C/P ratio and the dual effect of different metals like NiSO₄ on lipid and carotenoid production by red oleaginous yeasts, which in turn significant for enhancing the coproduction of lipid and carotenoid by R. glutinis. Full article

Torulene is a promising pink pigment, produced only by yeasts and fungi, and its production is still in a developing stage due to the low production rate. Accordingly, this study focuses on maximizing torulene production by Rhodotorula glutinis using shaken flask fermentation. The effect of different nitrogen sources, and C/N and C/S ratios on lipid and carotenoid production by R. glutinis was studied using 60 g/L glucose. The largest cells filled with golden fluorescence lipid bodies were observed using fluorescence microscopy when peptone was used as a nitrogen source. The highest total pigment (0.947 mg/L) and carotenoid relative productivity (Car-RP) (89.04 µg/g) were obtained at C/N 146 and C/S 120, and with ammonium sulfate as a nitrogen source, with 62% torulene domination using High Performance Liquid Chromatography (HPLC) for identification. Under a high C/N ratio, regardless of the C/S ratio, the carotenoid synthesis rate decreased after three days while the lipid synthesis rate kept increasing to the sixth day. Interestingly, after adding 0.7 mM Al₂(SO₄)₃ to the optimized medium, the total pigment and Car-RP (2.2 mg/L and 212.9 µg/g) sharply increased, producing around 2.16 mg/L torulene (98%) with around 50% decrease in lipid yield. This is the first report on the role of Al₂(SO₄)₃ for enhancing torulene production under lipogenesis condition, which could be used as a potential tool for torulene production. Full article

(1) Background: Lipids derived from oleaginous microbes have become promising alternative feedstocks for biodiesel. This is mainly because the lipid production rate from microbes is one to two orders of magnitude higher than those of energy crops. However, the conventional process for converting these lipids to biodiesel still requires a large amount of energy and organic solvents; (2) Methods: In this study, an oleaginous yeast, Rhodotorula glutinis, was used for direct transesterification without lipid pre-extraction to produce biodiesel, using sulfuric acid or sodium hydroxide as a catalyst. Such processes decreased the amount of energy and organic solvents required simultaneously; (3) Results: When 1 g of dry R. glutinis biomass was subject to direct transesterification in 20 mL of methanol catalyzed by 0.6 M H₂SO₄ at 70 °C for 20 h, the fatty acid methyl ester (FAME) yield reached 111%. Using the same amount of biomass and methanol loading but catalyzed by 1 g/L NaOH at 70 °C for 10 h, the FAME yield reached 102%. The acid-catalyzed process showed a superior moisture tolerance; when the biomass contained 70% moisture, the FAME yield was 43% as opposed to 34% of the base-catalyzed counterpart; (4) Conclusions: Compared to conventional transesterification, which requires lipid pre-extraction, direct transesterification not only simplifies the process and shortens the reaction time, but also improves the FAME yield. Full article

The global dependence on finite fossil fuel-derived energy is of serious concern given the predicted population increase. Over the past decades, bio-refining of woody biomass has received much attention, but data on food waste refining are sorely lacking, despite annual and global deposition of 1.3 billion tons in landfills. In addition to negative environmental impacts, this represents a squandering of valuable energy, water and nutrient resources. The potential of carbohydrate-rich food waste (CRFW) for biofuel (by Rhodotorulla glutinis fermentation) and biogas production (by calculating theoretical methane yield) was therefore investigated using a novel integrated bio-refinery approach. In this approach, hydrolyzed CRFW from three different conditions was used for Rhodotorulla glutinis cultivation to produce biolipids, whilst residual solids after hydrolysis were characterized for methane recovery potential via anaerobic digestion. Initially, CRFW was hydrolysed using thermal- (Th), chemical- (Ch) and Th-Ch combined hydrolysis (TCh), with the CRFW-leachate serving as a control (Pcon). Excessive foaming led to the loss of TCh cultures, while day-7 biomass yields were similar (3.4–3.6 g dry weight (DW) L⁻¹) for the remaining treatments. Total fatty acid methyl ester (FAME) content of R. glutinis cultivated on CRFW hydrolysates were relatively low (~6.5%) but quality parameters (i.e., cetane number, density, viscosity and higher heating values) of biomass extracted biodiesel complied with ASTM standards. Despite low theoretical RS-derived methane potential, further research under optimised and scaled conditions will reveal the potential of this approach for the bio-refining of CRFW for energy recovery and value-added co-product production. Full article