Fatty acid biosynthesis during the life cycle of the ascomycetous yeast Debaryomyces etchellsii cultivated on a non-fermentable substrate, i.e. glycerol, in nitrogen rich media (NRM) and nitrogen ...limited media (NLM) has been studied. Although considerable activities of key lipogenic enzymes, such as ATPcitrate lyase (ACL) and malic enzyme (ME), were detected in vegetative cells during asexual proliferation (which occurred in the first growth stages in both NRM and NLM), lipid accumulation was restricted due to the high activities of NAD super(+)-isocitrate dehydrogenase (NAD super(+)-ICDH). A similar enzymatic profile has been found in ascii and free ascospores produced in NRM; thus lipid accumulation was low. On the contrary, very high activities of both ACL and ME and low activities of NAD super(+)-ICDH were detected in ascii and free ascospores produced in NLM resulting in lipid accumulation. Neutral lipids (NL) were the predominant fraction of cellular lipids produced in vegetative cells and ascospores in both NRM and NLM. On the other hand, phospholipids (P) were the major polar lipids while glycolipids (G) were synthesized in low proportions. During transition from asexual to sexual phase, the percentage of NL increased with a significant decrease of P and, to a lesser extent, of G. High quantities of linoleic acid were found esterified in polar lipids, especially in P, during the vegetative stage of growth, while, with a few exceptions, during transition from asexual to sexual stage, linoleic acid concentration decreased markedly, mainly in P, while oleic acid concentration increased.
Alterations of the mycobiota composition associated with Crohn's disease (CD) are challenging to link to defining elements of pathophysiology, such as poor injury repair. Using culture-dependent and ...-independent methods, we discovered that
preferentially localized to and was abundant within incompletely healed intestinal wounds of mice and inflamed mucosal tissues of CD human subjects.
cultures from injured mice and inflamed CD tissues impaired colonic healing when introduced into injured conventionally raised or gnotobiotic mice. We reisolated
from injured areas of these mice, fulfilling Koch's postulates. Mechanistically,
impaired mucosal healing through the myeloid cell-specific type 1 interferon-CCL5 axis. Taken together, we have identified a fungus that inhabits inflamed CD tissue and can lead to dysregulated mucosal healing.
b-Glucosidase production by Debaryomyces pseudopolymorphus UCLM-NS7A using a simple nutrient medium containing cellobiose was evaluated under several biochemical and physiological parameters in ...submerged fermentation. Enzyme induction was also examined using different carbon and nitrogen sources. Cellobiose and ammonium nitrate were the best C and N sources to enhance b-glucosidase production. The addition of NaCl, MgSO sub(4), yeast extract, ethanol and Tween 80 to the nutrient medium before inoculation was also compared. A factorial design to optimize enzyme production was developed using four variables that most influenced b-glucosidase production and data analyzed by the response surface method. Optimal conditions to produce b-glucosidase in shake-flasks were 1.25% cellobiose, 0.05% Tween 80, 0.4% NH sub(4)NO sub(3) over 72 hours. In another factorial design to further increase enzyme production, a lab fermenter using prior-determined shake-flask optimized conditions resulted in higher b-glucosidase titres at 72 hours, pH controlled at 6.25 and agitation of 200 rpm.
Globally, rice is becoming more vulnerable to arsenic (As) pollution, posing a serious threat to public food safety. Previously Debaryomyces hansenii was found to reduce grain As content of rice. To ...better understand the underlying mechanism, we performed a genome analysis to identify the key genes in D. hansenii responsible for As tolerance and plant growth promotion. Notably, genes related to As resistance (ARR, Ycf1, and Yap) were observed in the genome of D. hansenii. The presence of auxin pathway and glutathione metabolism-related genes may explain the plant growth-promoting potential and As tolerance mechanism of this novel yeast strain. The genome annotation of D. hansenii indicated that it contains a repertoire of genes encoding antioxidants, well corroborated with the in vitro studies of GST, GR, and glutathione content. In addition, the effect of D. hansenii on gene expression profiling of rice plants under As stress was also examined. The Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed 307 genes, annotated in D. hansenii-treated rice, related to metabolic pathways (184), photosynthesis (12), glutathione (10), tryptophan (4), and biosynthesis of secondary metabolite (117). Higher expression of regulatory elements like AUX/IAA and WRKY transcription factors (TFs), and defense-responsive genes dismutases, catalases, peroxiredoxin, and glutaredoxins during D. hansenii+As exposure was also observed. Combined analysis revealed that D. hansenii genes are contributing to stress mitigation in rice by supporting plant growth and As-tolerance. The study lays the foundation to develop yeast as a beneficial biofertilizer for As-prone areas.
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•DEGs in rice assert with in vitro GST, GR, and genes (ACR2, ACR3, YAP1, YCF1) of D. hansenii.•D. hansenii genome revealed CC: 12304058 bp, G+C-36.18%, CDS: 6072, tRNAs: 243, and rRNAs:17.•D. hansenii modulates genes related to glutathione, auxin, and photosynthesis in rice.
•Debaryomyces hansenii UFV-1 β-glucosidase was produced and purified.•The enzyme was characterised and immobilised in calcium alginate.•Immobilisation assures higher enzymatic pH and thermal ...stabilities.•Free and immobilised enzymes were able to hydrolyse isoflavones in soy molasses.
An intracellular β-glucosidase from Debaryomyceshansenii UFV-1 was produced in an YP medium with cellobiose as the carbon source. This enzyme was purified, characterised and presented a Mr of 65.15kDa. Yeast cells containing the intracellular β-glucosidase were immobilised in calcium alginate. The free β-glucosidase and immobilised cells containing the enzyme presented optima values of pH and temperature of 6.0 and 45°C and 5.5 and 50°C, respectively. The free enzyme maintained 62% and 47% of its original activity after 90days at 4°C and after 15days at room temperature, respectively. The immobilisation process resulted in higher enzyme thermostability at 45 and 50°C. Soy molasses treatment with the free enzyme and the immobilised cells containing β-glucosidase, for 2h at 40°C, promoted efficient hydrolysis of isoflavone glicosides to their aglycon forms. The results suggest that this enzyme could be used in the food industry, in the free or immobilised forms, for a safe and efficient process to hydrolyse isoflavone glycosides in soy molasses.
The influence of endophytic microbial community on plant growth and disease resistance is of considerable importance. Prior research indicates that pre-treatment of kiwifruit with the biocontrol ...yeast Debaryomyces hansenii suppresses gray mold disease induced by Botrytis cinerea. However, the specific underlying mechanisms remain unclear. In this study, Metagenomic sequencing was utilized to analyze the composition of the endophytic microbiome of kiwifruit under three distinct conditions: the healthy state, kiwifruit inoculated with B. cinerea, and kiwifruit treated with D. hansenii prior to inoculation with B. cinerea. Results revealed a dominance of Proteobacteria in all treatment groups, accompanied by a notable increase in the relative abundance of Actinobacteria and Firmicutes. Ascomycota emerged as the major dominant group within the fungal community. Treatment with D. hansenii induced significant alterations in microbial community diversity, specifically enhancing the relative abundance of yeast and exerting an inhibitory effect on B. cinerea. The introduction of D. hansenii also enriched genes associated with energy metabolism and signal transduction, positively influencing the overall structure and function of the microbial community. Our findings highlight the potential of D. hansenii to modulate microbial dynamics, inhibit pathogenic organisms, and positively influence functional attributes of the microbial community.
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•Metagenome characterized response of kiwifruit to B. cinerea and D. hansenii.•The endo-microbiota of kiwifruit are modulated by the application of D. hansenii.•D. hansenii modulates microbial community structure, increasing disease resistance.•D. hansenii modulates microbial function, enhancing resistance in kiwifruit.
The cytoplasmic virus-like element pWR1A from Debaryomyces robertsiae encodes a toxin (DrT) with similarities to the Pichia acaciae killer toxin PaT, which acts by importing a toxin subunit (PaOrf2) ...with tRNA anticodon nuclease activity into target cells. As for PaT, loss of the tRNA methyltransferase Trm9 or overexpression of tRNA super(Gln) increases DrT resistance and the amount of tRNA super(Gln) is reduced upon toxin exposure or upon induced intracellular expression of the toxic DrT subunit gene DrORF3, indicating DrT and PaT to share the same in vivo target. Consistent with a specific tRNase activity of DrOrf3, the protein cleaves tRNA super(Gln) but not tRNA super(Glu) in vitro. Heterologous cytoplasmic expression identified DrOrf5 as the DrT specific immunity factor; it confers resistance to exogenous DrT as well as to intracellular expression of DrOrf3 and prevents tRNA depletion by the latter. The PaT immunity factor PaOrf4, a homologue of DrOrf5 disables intracellular action of both toxins. However, the DrT protection level mediated by PaOrf4 is reduced compared to DrOrf5, implying a recognition mechanism for the cognate toxic subunit, leading to incomplete toxicity suppression of similar, but non-cognate toxic subunits.
ABSTRACT
Nine morphologically distinct halophilic yeasts were isolated from Makgadikgadi and Sua pans, as pristine and extreme environments in Botswana. Screening for biosurfactant production showed ...that Rhodotorula mucilaginosa SP6 and Debaryomyces hansenii MK9 exhibited the highest biosurfactant activity using Xanthocercis zambesiaca seed powder as a novel and alternative inexpensive carbon substrate. Chemical characterization of the purified biosurfactants by Fourier Transform Infra-Red spectroscopy suggested that the biosurfactant from R. mucilaginosa SP6 was a rhamnolipid-type whereas the biosurfactant from D. hansenii MK9 was a sophorolipid-type. The two biosurfactants exhibited antimicrobial activities against eight pathogenic bacteria and fungal strains (Proteus vulgaris, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Micrococcus luteus, Cryptococcus neoformans, Candida albicans and Aspergilus niger). The sophorolopid-type biosurfactant was found to be the most potent among the antimicrobial drug resistant strains tested. The findings open up prospects for the development of environmentally friendly antimicrobial drugs that use an inexpensive source of carbon to reduce the costs associated with the production of biosurfactants.
Halophilic yeasts from the biggest saltpans in the whole world produce potential antimicrobial agents important in the era of increasing global antimicrobial drug resistance crisis.
•D. nepalensis significantly reduced black spot of jujube caused by A. alternate.•The formation of biofilms was an important biocontrol mechanism of D. nepalensis.•Release of QSMs was critical for ...cell growth and biofilm formation of D. nepalensis.•Phenylethanol improved biocontrol effect by promoting biofilm formation.
Microbial biocontrol agents have become an effective way to inhibit post-harvest diseases of fruits and vegetables, where antagonistic yeast with antimicrobial properties are often employed. In this study, Debaryomyces nepalensis, isolated from the leaves of jujube and identified with internal transcribed spacer sequences, can effectively control the post-harvest black spot of jujube caused by Alternaria alternate, even though it showed no direct inhibitory effects on A. alternate. Phenylethanol, as a quorum sensing molecule, was identified by HPLC to be one of the major metabolites during the culture of D. nepalensis. Phenylethanol could promote the biofilm formation ability of D. nepalensis and increase its adhesion to the surface of jujube fruit, and the control effect of 2 mmol L−1 phenylethanol combined with D. nepalensis on jujube fruit black spot was increased by 15 % compared with D. nepalensis alone. In conclusion, the results of this work provided a new perspective for improving the biological control efficiency of D. nepalensis.
•Alkali-tolerant D. hansenii was employed for SCP production from biogas slurry.•D. hansenii grew optimally at pH 8.5, and could tolerate 0.4 M NaCl addition.•D. hansenii was able to efficiently ...utilize acetate as the carbon source.•97.4 % NH4+-N conversion efficiency was achieved in fed batch fermentation.•The cell biomass titer and productivity reached 32.21 g/L and 0.32 g/L·h−1.
Production of single cell protein (SCP) by recovering ammonia nitrogen from biogas slurry shows great potential against protein scarcity and unsustainable production of plant and animal proteins. Herein, a high-alkali-salt-tolerant yeast strain, Debaryomyces hansenii JL8-0, was isolated and demonstrated for high-efficient SCP production. This strain grew optimally at pH 8.50 and 2500 mg/L NH4+-N, and it could efficiently utilize acetate as the additional carbon source. Under optimal conditions, SCP biomass of 32.21 g/L and productivity of 0.32 g/L·h−1 were obtained in fed-batch fermentation. Remarkably, nearly complete (97.40 %) ammonia nitrogen from biogas slurry was recovered, probably due to its high affinity for NH4+-N. Altogether, this strain showed advantages in terms of cell biomass titer, productivity, and yield. A cultivation strategy was proposed by co-culturing D. hansenii with other compatible yeast strains to achieve high-efficient SCP production from biogas slurry, which could be a promising alternative technology for biogas slurry treatment.
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