Cultivation of yeasts on liquid digestate to remove organic pollutants and nutrients and for potential application as co-culture with microalgae.

In this study, the growth of yeast and yeast-like fungi in the liquid digestate from vegetable wastes was investigated in order to remove nutrients and organic pollutants, and for their application as co-culture members with green microalgae. The studied yeast strains were characterized for their assimilative and enzymatic profiles as well as temperature requirements. In the first experimental stage, the growth dynamics of each strain were determined, allowing to select the best yeasts for further studies. In the subsequent stage, the ability of selectants to remove organic pollutants was assessed. Different cultivation media containing respectively 1:3, 1:1, 3:1 vol ratio of liquid digestate and the basal minimal medium were used. Among all tested yeast strains, Rhodotorula mucilaginosa DSM 70825 showed the most promising results, demonstrating the highest potential for removing organic substrates and nutrients. Depending on the medium, this strain achieved 50-80% sCOD, 45-60% tVFAs, 21-45% TN, 33-52% PO43- reduction rates. Similar results were obtained for the strain Candida sp. OR687571. The high nutrient and organics removal efficiency by these yeasts could likely be linked to their ability to assimilate xylose (being the main source of carbon in the liquid digestate). In culture media containing liquid digestate, both yeast strains achieved good viability and proliferation potential. In the liquid digestate medium, R. mucilaginosa and Candida sp. showed vitality at the level of 51.5% and 45.0%, respectively. These strains seem to be a good starting material for developing effective digestate treatment strategies involving monocultures and/or consortia with other yeasts or green microalgae.

Exploring the Efficacy of Using Geotrichum fermentans, Rhodotorula rubra, Kluyveromyce marxiamus, Clay Minerals, and Walnut Nutshells for Mycotoxin Remediation.

The aim of this study was to evaluate the effectiveness of nine different biological compounds to reduce mycotoxins concentrations. The hypothesis of this study was that a static in vitro gastrointestinal tract model, as an initial screening tool, can be used to simulate the efficacy of Geotrichum fermentans, Rhodotorula rubra, Kluyveromyce marxiamus yeast cell walls and their polysaccharides, red and white clay minerals, and walnuts nutshells claiming to detoxify AFB1, ZEA, DON, and T-2 toxin mycotoxins. Mycotoxin concentrations were analyzed using high-performance liquid chromatography (HPLC) with fluorescent (FLD) and ultraviolet detectors (UV). The greatest effects on reducing mycotoxin concentrations were determined as follows: for AFB1, inserted G. fermentans cell wall polysaccharides and walnut nutshells; for ZEA, inserted R. rubra and G. fermentans cell walls and red clay minerals; for DON, R. rubra cell wall polysaccharides and red clay minerals; and for T-2 toxin, R. rubra cell walls, K. marxianus, and G. fermentans cell wall polysaccharides and walnut nutshells. The present study indicated that selected mycotoxin-detoxifying biological compounds can be used to decrease mycotoxin concentrations.

Enhancing Selenium Accumulation in Rhodotorula mucilaginosa Strain 6S Using a Proteomic Approach for Aquafeed Development.

It is known that selenium (Se) is an essential trace element, important for the growth and other biological functions of fish. One of its most important functions is to contribute to the preservation of certain biological components, such as DNA, proteins, and lipids, providing protection against free radicals resulting from normal metabolism. The objective of this study was to evaluate and optimize selenium accumulation in the native yeast Rhodotorula mucilaginosa 6S. Sodium selenite was evaluated at different concentrations (5-10-15-20-30-40 mg/L). Similarly, the effects of different concentrations of nitrogen sources and pH on cell growth and selenium accumulation in the yeast were analyzed. Subsequently, the best cultivation conditions were scaled up to a 2 L reactor with constant aeration, and the proteome of the yeast cultured with and without sodium selenite was evaluated. The optimal conditions for biomass generation and selenium accumulation were found with ammonium chloride and pH 5.5. Incorporating sodium selenite (30 mg/L) during the exponential phase in the bioreactor after 72 h of cultivation resulted in 10 g/L of biomass, with 0.25 mg total Se/g biomass, composed of 25% proteins, 15% lipids, and 0.850 mg total carotenoids/g biomass. The analysis of the proteomes associated with yeast cultivation with and without selenium revealed a total of 1871 proteins. The results obtained showed that the dynamic changes in the proteome, in response to selenium in the experimental medium, are directly related to catalytic activity and oxidoreductase activity in the yeast. R. mucilaginosa 6S could be an alternative for the generation of selenium-rich biomass with a composition of other nutritional compounds also of interest in aquaculture, such as proteins, lipids, and pigments.

De Novo Synthesis of Resveratrol from Sucrose by Metabolically Engineered Yarrowia lipolytica.

Resveratrol, a phenylpropanoid compound, exhibits diverse pharmacological properties, making it a valuable candidate for health and disease management. However, the demand for resveratrol exceeds the capacity of plant extraction methods, necessitating alternative production strategies. Microbial synthesis offers several advantages over plant-based approaches and presents a promising alternative. Yarrowia lipolytica stands out among microbial hosts due to its safe nature, abundant acetyl-CoA and malonyl-CoA availability, and robust pentose phosphate pathway. This study aimed to engineer Y. lipolytica for resveratrol production. The resveratrol biosynthetic pathway was integrated into Y. lipolytica by adding genes encoding tyrosine ammonia lyase from Rhodotorula glutinis, 4-coumarate CoA ligase from Nicotiana tabacum, and stilbene synthase from Vitis vinifera. This resulted in the production of 14.3 mg/L resveratrol. A combination of endogenous and exogenous malonyl-CoA biosynthetic modules was introduced to enhance malonyl-CoA availability. This included genes encoding acetyl-CoA carboxylase 2 from Arabidopsis thaliana, malonyl-CoA synthase, and a malonate transporter protein from Bradyrhizobium diazoefficiens. These strategies increased resveratrol production to 51.8 mg/L. The further optimization of fermentation conditions and the utilization of sucrose as an effective carbon source in YP media enhanced the resveratrol concentration to 141 mg/L in flask fermentation. By combining these strategies, we achieved a titer of 400 mg/L resveratrol in a controlled fed-batch bioreactor. These findings demonstrate the efficacy of Y. lipolytica as a platform for the de novo production of resveratrol and highlight the importance of metabolic engineering, enhancing malonyl-CoA availability, and media optimization for improved resveratrol production.

ß-Carotene production from sugarcane molasses by a newly isolated Rhodotorula toruloides L/24-26-1.

Production of carotenoids by yeast fermentation is an advantaged technology due to its easy scaling and safety. Nevertheless, carotenoid production needs an economic culture medium and other efficient yeast stains. The study aims to isolate and identify a yeast strain capable of producing carotenoids using a cost-effective substrate. A new strain was identified as Rhodotorula toruloides L/24-26-1, which can produce carotenoids at different pretreated and unpretreated sugarcane molasses concentrations (40 and 80 g/L). The highest biomass concentration (18.6 ± 0.6 g/L) was reached in the culture using 80 g/L of hydrolyzed molasses. On the other hand, the carotenoid accumulation reached the maximum value using pretreated molasses at 40 g/L (715.4 ± 15.1 µg/g d.w). In this case, the ß-carotene was 1.5 times higher than that on the control medium. The yeast growth in molasses was not correlated with carotenoid production. The most outstanding production of The DPPH, ABTS, and FRAP tests demonstrated the antioxidant activity of the obtained carotenogenic extracts. This research demonstrated the R. toruloides L/24-26-1 strain biotechnological potential for carotenoid compounds. The yeast produces carotenoids with antioxidant activity in an inexpensive medium, such as sulfuric acid pretreated and unpretreated molasses.

Bioproduction of yeast single cell oil with acute oral toxicity study intended for edible oil application.

Human nutrition and health rely on edible oils. Global demand for edible oils is expanding, necessitating the discovery of new natural oil sources subjected to adequate quality and safety evaluation. However, in contrast to other agricultural products, India's edible oil supply is surprisingly dependent on imports. The microbial oil is generated by fermentation of oleaginous yeast Rhodotorula mucilaginosa IIPL32 MTCC 25056 using biodiesel plant byproduct crude glycerol as a fermentable carbon source. Enriched with monounsaturated fatty acid, nutritional indices mapping based on the fatty acid composition of the yeast SCO, suggested its plausible use as an edible oil blend. In the present study, acute toxicity evaluation of the yeast SCO in C57BL/6 mice has been performed by randomly dividing the animals into 5 groups with 50, 300, 2000, and 5000 mg/Kg yeast SCO dosage, respectively, and predicted the median lethal dose (LD50). Detailed blood biochemistry and kidney and liver histopathology analyses were also reported. The functions of the liver enzymes were also evaluated to check and confirm the anticipated toxicity. To determine cell viability and in vitro biocompatibility, the 3T3-L1 cell line and haemolysis tests were performed. The results suggested the plausible use of yeast SCO as an edible oil blend due to its non-toxic nature in mice models.

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.

Rhodotorula mucilaginosa A8, a potential helper strain in a vitamin C microbial fermentation process.

In the vitamin C microbial fermentation system, oxidative stress limits the growth and 2-keto-l-gulonic acid (2-KLG, the precursor of vitamin C) production of Ketogulonicigenium vulgare. Most Bacillus strains, as helper strains, have been reported to release key biomolecules to reduce oxidative stress and promote the growth and 2-KLG production of K. vulgare. To understand the specific mechanism by which the helper strain and K. vulgare interact to reduce oxidative stress, a novel helper strain, Rhodotorula mucilaginosa A8, was used to construct a consortium in the co-culture fermentation system. Based on the activities of the antioxidant enzymes and quantitative polymerase chain reaction (qPCR) analysis, R. mucilaginosa A8 could reduce oxidative stress and increase 2-KLG production in K. vulgare by upregulating antioxidant enzyme activities and related gene-expression levels. In addition, the carotenoids of R. mucilaginosa promoted 2-KLG production in K. vulgare. Coculture of R. mucilaginosa with K. vulgare increased the yield of carotenoids. This study suggested that helper strains with the ability to reduce oxidative stress in K. vulgare would likely act as potential helper strains for facilitating 2-KLG biosynthesis. This work could provide a theoretical basis for the search for potential helper strains for vitamin C microbial fermentation and for the construction of synthetic microbial communities to produce valuable products.

Nitrogen starvation causes lipid remodeling in Rhodotorula toruloides.

BACKGROUND: The oleaginous yeast Rhodotorula toruloides is a promising chassis organism for the biomanufacturing of value-added bioproducts. It can accumulate lipids at a high fraction of biomass. However, metabolic engineering efforts in this organism have progressed at a slower pace than those in more extensively studied yeasts. Few studies have investigated the lipid accumulation phenotype exhibited by R. toruloides under nitrogen limitation conditions. Consequently, there have been only a few studies exploiting the lipid metabolism for higher product titers. RESULTS: We performed a multi-omic investigation of the lipid accumulation phenotype under nitrogen limitation. Specifically, we performed comparative transcriptomic and lipidomic analysis of the oleaginous yeast under nitrogen-sufficient and nitrogen deficient conditions. Clustering analysis of transcriptomic data was used to identify the growth phase where nitrogen-deficient cultures diverged from the baseline conditions. Independently, lipidomic data was used to identify that lipid fractions shifted from mostly phospholipids to mostly storage lipids under the nitrogen-deficient phenotype. Through an integrative lens of transcriptomic and lipidomic analysis, we discovered that R. toruloides undergoes lipid remodeling during nitrogen limitation, wherein the pool of phospholipids gets remodeled to mostly storage lipids. We identify specific mRNAs and pathways that are strongly correlated with an increase in lipid levels, thus identifying putative targets for engineering greater lipid accumulation in R. toruloides. One surprising pathway identified was related to inositol phosphate metabolism, suggesting further inquiry into its role in lipid accumulation. CONCLUSIONS: Integrative analysis identified the specific biosynthetic pathways that are differentially regulated during lipid remodeling. This insight into the mechanisms of lipid accumulation can lead to the success of future metabolic engineering strategies for overproduction of oleochemicals.

Enhanced high ß-carotene yeast cell production by Rhodotorula paludigena CM33 and in vitro digestibility in aquatic animals.

This study assessed Rhodotorula paludigena CM33's growth and ß-carotene production in a 22-L bioreactor for potential use as an aquatic animal feed supplement. Optimizing the feed medium's micronutrient concentration for high-cell-density fed-batch cultivation using glucose as the carbon source yielded biomass of 89.84 g/L and ß-carotene concentration of 251.64 mg/L. Notably, using sucrose as the carbon source in feed medium outperforms glucose feeds, resulting in a ß-carotene concentration of 285.00 mg/L with a similar biomass of 87.78 g/L. In the fed-batch fermentation using Sucrose Feed Medium, R. paludigena CM33 exhibited high biomass production rates (Qx) of 0.91 g/L.h and remarkable ß-carotene production rates (Qp) of 2.97 mg/L.h. In vitro digestibility assays showed that R. paludigena CM33, especially when cultivated using sucrose, enhances protein digestibility affirming its suitability as an aquatic feed supplement. Furthermore, R. paludigena CM33's nutrient-rich profile and probiotic potential make it an attractive option for aquatic nutrition. This research highlights the importance of cost-effective carbon sources in large-scale ß-carotene production for aquatic animal nutrition.

Biotechnological potential of red yeast isolated from birch forests in Poland.

OBJECTIVES: This study aimed to isolate red yeast from sap, bark and slime exudates collected from Polish birch forests and then assessment of their biotechnological potential. RESULTS: 24 strains of red yeast were isolated from the bark, sap and spring slime fluxes of birch (Betula pendula). Strains belonging to Rhodotorula mucilaginosa (6), Rhodosporidiobolus colostri (4), Cystrofilobasidium capitaum (3), Phaffia rhodozyma (3) and Cystobasidium psychroaquaticum (3) were dominant. The highest efficiency of carotenoid biosynthesis (5.04 mg L-1) was obtained by R. mucilaginosa CMIFS 004, while lipids were most efficiently produced by two strains of P. rhodozyma (5.40 and 5.33 g L-1). The highest amount of exopolysaccharides (3.75 g L-1) was produced by the R. glutinis CMIFS 103. Eleven strains showed lipolytic activity, nine amylolytic activity, and only two proteolytic activity. The presence of biosurfactants was not found. The growth of most species of pathogenic moulds was best inhibited by Rhodotorula yeasts. CONCLUSION: Silver birch is a good natural source for the isolation of new strains of red yeast with wide biotechnological potential.

Chemoenzymatic Asymmetric Synthesis of Chiral Triazole Fungicide (R)-Tebuconazole in High Optical Purity Mediated by an Epoxide Hydrolase from Rhodotorula paludigensis.

Tebuconazole is a chiral triazole fungicide used globally in agriculture as a racemic mixture, but its enantiomers exhibit significant enantioselective dissimilarities in bioactivity and environmental behaviors. The steric hindrance caused by the tert-butyl group makes it a great challenge to synthesize tebuconazole enantiomers. Here, we designed a simple chemoenzymatic approach for the asymmetric synthesis of (R)-tebuconazole, which includes the biocatalytic resolution of racemic epoxy-precursor (2-tert-butyl-2-[2-(4-chlorophenyl)ethyl] oxirane, rac-1a) by Escherichia coli/Rpeh whole cells expressed epoxide hydrolase from Rhodotorula paludigensis (RpEH), followed by a one-step chemocatalytic synthesis of (R)-tebuconazole. It was observed that (S)-1a was preferentially hydrolyzed by E. coli/Rpeh, whereas (R)-1a was retained with a specific activity of 103.8 U/g wet cells and a moderate enantiomeric ratio (E value) of 13.4, which was remarkably improved to 43.8 after optimizing the reaction conditions. Additionally, a gram-scale resolution of 200 mM rac-1a was performed using 150 mg/mL E. coli/Rpeh wet cells, resulting in the retention of (R)-1a in a 97.0% ees, a 42.5% yields, and a 40.5 g/L/d space-time yield. Subsequently, the synthesis of highly optical purity (R)-tebuconazole (>99% ee) was easily achieved through the chemocatalytic ring-opening of the epoxy-precursor (R)-1a with 1,2,4-triazole. To elucidate insight into the enantioselectivity, molecular docking simulations revealed that the unique L-shaped substrate-binding pocket of RpEH plays a crucial role in the enantioselective recognition of bulky 2,2-disubstituted oxirane 1a.

Identification of Irpex and Rhodotorula on surveillance bronchoscopy in a pediatric lung transplant recipient: A case report and review of literature of these atypical fungal organisms.

BACKGROUND: Invasive fungal disease (IFD) is a frequent complication in pediatric lung transplant recipients, occurring in up to 12% of patients in the first year. Risk factors for infection include impaired lung defenses and intense immunosuppressive regimens. While most IFD occurs from Aspergillus, other fungal conidia are continuously inhaled, and infections with fungi on a spectrum of human pathogenicity can occur. CASE REPORT: We report a case of a 17-year-old lung transplant recipient in whom Irpex lacteus and Rhodotorula species were identified during surveillance bronchoscopy. She was asymptomatic and deemed to be colonized by Irpex lacteus and Rhodotorula species following transplant. 2 years after transplantation, she developed a fever, respiratory symptoms, abnormal lung imaging, and histological evidence of acute and chronic bronchitis on transbronchial biopsy. After developing symptoms concerning for a pulmonary infection and graft dysfunction, she was treated for a presumed IFD. Unfortunately, further diagnostic testing could not be performed at this time given her tenuous clinical status. Despite the initiation of antifungal therapy, her graft function continued to decline resulting in a second lung transplantation. CONCLUSIONS: This case raises the concern for IFD in lung transplant recipients from Irpex species. Further investigation is needed to understand the pathogenicity of this organism, reduce the incidence and mortality of IFD in lung transplant recipients, and refine the approach to diagnosis and manage the colonization and isolation of rare, atypical fungal pathogens in immunocompromised hosts.

Formation of Sb2O3 microcrystals by Rhodotorula mucilaginosa.

Antimony (Sb) pollution seriously endangers ecological environment and human health. Microbial induced mineralization can effectively convert metal ions into more stable and less soluble crystalline minerals by extracellular polymeric substance (EPS). In this study, an efficient Sb-resistant Rhodotorula mucilaginosa (R. mucilaginosa) was screened, which can resist 41 mM Sb(III) and directly transform Sb(III) into Sb2O3 microcrystals by EPS. The removal efficiency of R. mucilaginosa for 22 mM Sb(III) reached 70% by converting Sb(III) to Sb2O3. The components of supernatants as well as the effects of supernatants and pH on Sb(III) mineralization verified that inducible and non-inducible extracellular protein/polysaccharide biomacromolecules play important roles in the morphologies and sizes control of Sb2O3 formed by R. mucilaginosa respectively. Sb2O3 microcrystals with different morphologies and sizes can be prepared by the regulation of inducible and non-inducible extracellular biomacromolecules secreted by R. mucilaginosa. This is the first time to identify that R. mucilaginosa can remove Sb(III) by transforming Sb(III) into Sb2O3 microcrystals under the control of EPS. This study contributes to our understanding for Sb(III) biomineralization mechanisms and provides strategies for the remediation of Sb-contaminated environment.

New neuroprotective derivatives of cinnamic acid by biotransformation.

Microbial transformation is extensively utilized to generate new metabolites in bulk amounts with more specificity and improved activity. As cinnamic acid was reported to exhibit several important pharmacological properties, microbial transformation was used to obtain its new derivatives with enhanced biological activities. By manipulating the 2-stage fermentation protocol of biotransformation, five metabolites were produced from cinnamic acid. Two of them were new derivatives; N-propyl cinnamamide 2̲ and 2-methyl heptyl benzoate 3̲ produced by Alternaria alternata. The other 3 metabolites, p-hydroxy benzoic acid 4̲, cinnamyl alcohol 5̲ and methyl cinnamate 6̲, were produced by Rhodotorula rubra, Rhizopus species and Penicillium chrysogeneum, respectively. Cinnamic acid and its metabolites were evaluated for their cyclooxygenase (COX) and acetylcholinesterase (AChE) inhibitory activities. Protection against H2O2 and Aß1-42 induced-neurotoxicity in human neuroblastoma (SH-SY5Y) cells was also monitored. Metabolite 4̲ was more potent as a COX-2 inhibitor than the parent compound with an IC50 value of 1.85 ± 0.07 µM. Out of the tested compounds, only metabolite 2̲ showed AChE inhibitory activity with an IC50 value of 8.27 µM. These results were further correlated with an in silico study of the binding interactions of the active metabolites with the active sites of the studied enzymes. Metabolite 3̲ was more potent as a neuroprotective agent against H2O2 and Aß1-42 induced-neurotoxicity than catechin and epigallocatechin-3-gallate as positive controls. This study suggested the two new metabolites 2̲ and 3̲ along with metabolite 4̲ as potential leads for neurodegenerative diseases associated with cholinergic deficiency, neurotoxicity or neuroinflammation.

Carotenoids production by Rhodosporidium paludigenum yeasts: Characterization of chemical composition, antioxidant and antimicrobial properties.

The high market potential imposed by natural carotenoids has turned the scientific interest in search for new strains, capable of synthesizing a wide spectrum of these pigments. In this study, Rhodosporidium paludigenum NCYC 2663 and 2664 were investigated for carotenoids production and lipid accumulation utilizing different carbon sources (glucose, fructose, sucrose, mixture of glucose: galactose). Strain R. paludigenum 2663 produced the highest total carotenoids titer (2.21 mg/L) when cultivated on sucrose, together with 4 g/L lipids (30% w/w content) and 7 g/L exopolysaccharides. In the case of R. paludigenum 2664, glucose favored the production of 2.93 mg/L total carotenoids and 1.57 g/L lipids (31.8% w/w content). Analysis of the chemical profile during fermentation revealed that ß-carotene was the prominent carotenoid. Strain 2663 co-produced γ-carotene, torulene and torularhodin in lower amounts, whereas 2664 synthesized almost exclusively ß-carotene. The produced lipids from strain 2663 were rich in oleic acid, while the presence of linoleic acid was also detected in the lipoic fraction from strain 2664. The obtained carotenoid extracts exhibited antioxidant (IC50 0.14 mg/mL) and high antimicrobial activity, against common bacterial and fungal pathogenic strains. The results of this study are promising for the utilization of biotechnologically produced carotenoids in food applications.

Diversity, distribution, and bioprospecting potentials of carotenogenic yeast from mangrove ecosystem.

Microbial production of carotenoids has gained significant interest for its cost-effectiveness and sustainable nature. This study focuses on 47 red-pigmented yeasts isolated from sediments and plant parts of 13 species of mangrove trees. The relative abundance and distribution of these yeasts varied with plant species and plant parts. The highest number of red yeasts was associated with the mangrove plant Avicennia officinalis (32%). Notably, the leaves harbored the highest percentage (45%) of carotenogenic yeasts, and definite compartmentalization of these yeast species was noticed in mangrove plant parts. All the isolates were molecularly identified and they belonged to the genera of Rhodotorula, Rhodosporidiobolus, and Cryptococcus. The diversity of the pigmented yeasts isolated from A. officinalis was found to be the greatest. Among these strains, Rhodotorula mucilaginosa PV 8 was identified as the most potent producer of carotenoid pigment. Under optimized conditions of physical parameters - 28 °C, pH 5, and 15% salinity led to biomass production of 9.2 ± 0.12 g/L DCW and a pigment yield of 194.78 µg/g. The pigment produced by PV 8 was identified as ß-carotene by thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FT-IR). This ß-carotene demonstrated strong antioxidant activity. Moreover, the carotenoid displayed promising antibacterial activity against multidrug-resistant organisms, including Aeromonas sp. and Vibrio sp. In vitro studies revealed the probiotic traits of PV 8. The cytotoxicity of R. mucilaginosa PV 8 was assessed in the invertebrate model Artemia salina and the survival rate showed that it was non-toxic. Furthermore, the ß-carotene from PV 8 demonstrated the ability to transfer its vibrant color to various food products, maintaining color stability even under varied conditions. This research underscores the potential of R. mucilaginosa PV 8, as a versatile and valuable resource for the production of carotenoids.

Glucosylglycerol and proline reverse the effects of glucose on Rhodosporidium toruloides lifespan.

Rhodosporidium toruloides is a novel cell factory used to synthesis carotenoids, biosurfactants, and biofuel feedstocks. However, research on R. toruloides has generally centred on the manufacture of biochemicals, while analyses of its longevity have received scant attention. Understanding of R. toruloides longevity under different nutrient conditions could help to improve its biotechnological significance and metabolite production. Glucosylglycerol (GG) and proline are osmoprotectants that could revert the harmful effects of environmental stress. This study examined how GG and proline affect R. toruloides strain longevity under glucose nutrimental stress. Herein, we provide evidence that GG and proline enhance cell performance and viability. These compatible solutes neutralises the pro-ageing effects of high glucose (10% glucose) on the yeast cell and reverse its cellular stress. GG exhibits the greatest impact on lifespan extension at 100 mM, whereas proline exerts effect at 2 mM. Our data reveal that these compounds significantly affect the culture medium osmolarity. Moreso, GG and proline decreased ROS production and mitohormetic lifespan regulation, respectively. The data indicates that these solutes (proline and GG) support the longevity of R. toruloides at a pro-ageing high glucose culture condition.

Effect of Rhodotorula mucilaginosa inoculation on the aroma development of a fermented vegetables simulated system.

Fermented vegetables are known for their unique flavors and aromas, which are influenced by the complex microbial processes that occur during fermentation. Rhodotorula mucilaginosa is a red yeast strain that is frequently isolated from fermented vegetables. However, the specific mechanisms underlying their effects on aroma production remain unclear. In this study, a simulated system of vegetables fermented using vegetable juices was used to investigate the effects of R. mucilaginosa inoculation on aroma development. The results demonstrated that this red yeast strain could utilize the nutrients present in the vegetable juices to support its growth and reproduction. Moreover, the inoculation of fermented vegetable juices with this yeast strain led to an increase in the levels of umami amino acids and sweet amino acids. Furthermore, this yeast strain was found able to significantly reduce the content of sulfur-containing compounds, which may decrease the unpleasant odor of fermented vegetables. Additionally, the yeast strain was capable of producing high concentrations of aromatic compounds such as phenylethyl alcohol, methyl 2-methylbutyrate, methyl butyrate, and nonanoic acid in a minimum medium. However, only phenylethyl alcohol has been identified as a core aromatic compound in fermented vegetable juice. The three fermented vegetable juices exhibited significantly different flavor profiles according to comparative analysis. Therefore, the core flavor compounds found in fermented vegetables are primarily derived from the release and modification of endogenous flavors naturally present in the vegetables, facilitated by the yeast during fermentation.