Debaryomyces Nepalensis Research Articles

Thermal stability of xylose reductase from Debaryomyces nepalensis NCYC 3413: deactivation kinetics and structural studies

Abstract Deactivation kinetics, as well as the operational stability of enzymes, is crucial in economic feasibility of industrial enzymatic processes. In this study, thermal inactivation profiles of Debaryomyces nepalensis NCYC 3413 xylose reductase (DnXR) were obtained at different temperatures. Thermodynamic parameters of the deactivation process were determined by measuring the residual activity of the enzyme. Structural characteristics of the enzyme were determined using circular dichroism, differential scanning calorimetric techniques. Enzyme retained 75–80% activity at 35 °C after incubation for 5 h. At higher temperatures, the residual activity reduced at a faster rate where only 10% of the initial activity was retained in 10 min at 50 °C. Values of ΔH* (-300.47 kJmole−1), ΔG* (−530.66 kJ mole−1) and ΔS* (714.51 × 10−3 kJ K−1 mole−1) indicated that thermal deactivation of DnXR is enthalpy driven. In the presence of cofactor NADPH, melting temperature of the enzyme increased by 2 °C with a decrease in rate of thermal deactivation. Substrate found not to have a positive effect on thermal stability. This is the first report providing information on the thermal deactivation kinetics, thermodynamic parameter estimation and the influence of cofactor on thermal stability of Debaryomyces nepalensis NCYC 3413 xylose reductase.

Yeasts from Scarlet ibises (Eudocimus ruber): A focus on monitoring the antifungal susceptibility of Candida famata and closely related species.

This study aimed to identify yeasts from the gastrointestinal tract of scarlet ibises (Eudocimus ruber) and from plant material collected from the environment where they live. Then, the isolates phenotypically identified as Candida famata were submitted to molecular identification of their closely related species and evaluated for their antifungal susceptibility and possible resistance mechanisms to antifungal drugs. Cloacal swabs from 20 scarlet ibises kept in captivity at Mangal das Garças Park (Brazil), pooled stool samples (n = 20) and samples of trunks and hollow of trees (n = 20) obtained from their enclosures were collected. The samples were seeded on Sabouraud agar supplemented with chloramphenicol. The 48 recovered isolates were phenotypically identified as 15 Candida famata, 13 Candida catenulata, 2 Candida intermedia, 1 Candida lusitaniae, 2 Candida guilliermondii, 1 Candida kefyr, 1 Candida amapae, 1 Candida krusei, 8 Trichosporon spp., and 4 Rhodotorula spp. The C. famata isolates were further identified as 3 C. famata, 8 Debaryomyces nepalensis, and 4 C. palmioleophila. All C. famata and C. palmioleophila were susceptible to caspofungin and itraconazole, while one D. nepalensis was resistant to fluconazole and voriconazole. This same isolate and another D. nepalensis had lower amphotericin B susceptibility. The azole resistant strain had an increased efflux of rhodamine 6G and an alteration in the membrane sterol content, demonstrating multifactorial resistance mechanism. Finally, this research shows that scarlet ibises and their environment harbor C. famata and closely related species, including antifungal resistant isolates, emphasizing the need of monitoring the antifungal susceptibility of these yeast species.

Inhibition of Debaryomyces nepalensis xylose reductase by lignocellulose derived by-products

Xylose reductase (XR) is a biocatalyst that converts xylose to xylitol and it has a potential application in the enzyme based production of xylitol from lignocellulosic hydrolysates. However, the development of a successful XR based bioprocess for xylitol production is challenging, due to the presence of inhibitory lignocellulose derived by-products (LDBs) in hydrolysates. Though various methods have been developed to mitigate the toxic effects of LDBs, none of them were promising. One of the reasons for this, could be the lack of knowledge on the enzyme inhibition mechanisms. Therefore, for the first time, here we investigated mechanisms of XR inhibition by major LDBs using XR from Debaryomyces nepalensis. We found that phenol showed competitive inhibition of XR whereas gallic acid, vanillin, furfural, 5-hydroxymethylfurfural (HMF) and acetate exhibited mixed inhibition. The inhibitory constants (KI) of vanillin, phenol, gallic acid, furfural, HMF and acetate were found to be 0.1, 11, 32, 54, 45 and 100mM respectively. Moreover, the enzyme stability was drastically affected in the presence of phenols. In addition, molecular docking simulations performed using AutoDock 4.2.6 program revealed the putative binding sites of LDBs on XR and corroborated the experimental data.

Artificial neural network and regression coupled genetic algorithm to optimize parameters for enhanced xylitol production by Debaryomyces nepalensis in bioreactor

In this study, prediction ability and optimization ability of regression and artificial neural network (ANN) models were compared. The input variables used to predict xylose consumption, biomass and xylitol production by regression analysis and neural network model are temperature, fermentation time, pH, kLa, biomass and glycerol of previous data points. Determination of coefficient (R2) was used to assess the adequacy of the regression model and R2 for xylitol and biomass were 86.56% and 96.43% respectively. A multi layered feed forward neural network (ANN) of 5-10-2 topology has been developed to predict the xylitol production. Results showed that prediction accuracy of ANN was apparently higher when compared to regression model. Genetic algorithm (GA) was used to find the optimum parameters to enhance xylitol production. Optimization of fermentation parameters was carried out using hybrid regression GA and hybrid ANN GA with an optimum prediction error of 10% and 3.5% respectively. ANN coupled GA is considered to be the better optimization method due to its high accuracy and low prediction error and recommended to be employed for optimization of fermentative process.

Modeling and simulation of xylitol production in bioreactor by Debaryomyces nepalensis NCYC 3413 using unstructured and artificial neural network models

This study examines the use of unstructured kinetic model and artificial neural networks as predictive tools for xylitol production by Debaryomyces nepalensis NCYC 3413 in bioreactor. An unstructured kinetic model was proposed in order to assess the influence of pH (4, 5 and 6), temperature (25°C, 30°C and 35°C) and volumetric oxygen transfer coefficient kLa (0.14h−1, 0.28h−1 and 0.56h−1) on growth and xylitol production. A feed-forward back-propagation artificial neural network (ANN) has been developed to investigate the effect of process condition on xylitol production. ANN configuration of 6-10-3 layers was selected and trained with 339 experimental data points from bioreactor studies. Results showed that simulation and prediction accuracy of ANN was apparently higher when compared to unstructured mechanistic model under varying operational conditions. ANN was found to be an efficient data-driven tool to predict the optimal harvest time in xylitol production.

Multi response optimization for enhanced xylitol production by Debaryomyces nepalensis in bioreactor

In this study, the optimization of different process variables—pH (4–6), aeration rate (200–550 rpm) and agitation rate (0.6–1.8 vvm) were investigated using rotating simplex method and uniform design method to enhance xylitol production from xylose by D. nepalensis in a batch stirred tank bioreactor. Maximum xylitol productivity (0.576 g L−1 h−1) was obtained at pH 4.0, agitation 300 rpm and aeration 1.5 vvm by rotating simplex method. Individual optimum values of pH, agitation and aeration are 4.2, 370 rpm and 1.2 vvm, respectively, for productivity, 4.3, 350 rpm and 1.0 vvm, respectively for xylitol concentration and 4.4, 360 rpm and 0.8 vvm, respectively for yield. Using generalized distance approach, the simultaneous optimal values were found to be—pH 4.3, 370 rpm and 0.9 vvm. After multi-response analysis, batch fermentation at optimal operating conditions resulted in enhanced productivity (0.76 g L−1 h−1), xylitol concentration (59.4 g L−1) and yield (0.58 g g−1) with an increase of 76.74 % of xylitol productivity.

Biocontrol of Postharvest Anthracnose of Mango Fruit with Debaryomyces Nepalensis and Effects on Storage Quality and Postharvest Physiology.

Anthracnose is presently recognized as one of the most important postharvest disease of mango worldwide. To control the disease, chemical fungicides for a long time was widely used among fruit farmers, but recently found that pathogen had developed increasingly resistance to it. With people's growing desire of healthy and green food, finding new and environmentally friendly biological control approach was very necessary. In this paper, we provided a kind of new antagonistic yeast which enriched the strainresources and the efficacy of Debaryomyces nepalensis against postharvest anthracnose of mango fruit and the influence on quality parameters were investigated. The results showed that the decay incidence and lesion diameter of postharvest anthracnose of mango treated by D. nepalensis were significantly reduced compared with the control fruit stored at 25 °C for 30 d or at 15 °C for 40 d, and the higher concentration of D. nepalensis was, the better the efficacy of the biocontrol was. Study also found that 1 h was the best treatment duration and antagonistic yeast inoculated earlier had good biocontrol effect on anthracnose. Meanwhile, treatment by D. nepalensis could significantly reduce postharvest anthracnose of mango, delay the decrease in firmness, TSS, TA, and ascorbic acid value, and do not impair surface color during postharvest storage. Moreover, the increase in MDA (malondialdehyde) content and increase in cell membrane permeability of fruit treated by D. nepalensis was highly inhibited. The results suggested D. nepalensis treatment could not only maintain storage quality of mango fruit, but also decrease the decay incidence to anthracnose disease. All these results indicated that D. nepalensis has great potential for development of commercial formulations to control postharvest pathogens of mango fruit.

Phytase-producing capacity of yeasts isolated from traditional African fermented food products and PHYPk gene expression of Pichia kudriavzevii strains

Phytate is known as a strong chelate of minerals causing their reduced uptake by the human intestine. Ninety-three yeast isolates from traditional African fermented food products, belonging to nine species (Pichia kudriavzevii, Saccharomyces cerevisiae, Clavispora lusitaniae, Kluyveromyces marxianus, Millerozyma farinosa, Candida glabrata, Wickerhamomyces anomalus, Hanseniaspora guilliermondii and Debaryomyces nepalensis) were screened for phytase production on solid and liquid media. 95% were able to grow in the presence of phytate as sole phosphate source, P. kudriavzevii being the best growing species. A phytase coding gene of P. kudriavzevii (PHYPk) was identified and its expression was studied during growth by RT-qPCR. The expression level of PHYPk was significantly higher in phytate-medium, compared to phosphate-medium. In phytate-medium expression was seen in the lag phase. Significant differences in gene expression were detected among the strains as well as between the media. A correlation was found between the PHYPk expression and phytase extracellular activity.

Effect of kLa and Fed-batch Strategies for Enhanced Production of Xylitol by Debaryomyces nepalensis NCYC 3413

Effect of kLa and Fed-batch Strategies for Enhanced Production of Xylitol by Debaryomyces nepalensis NCYC 3413

Immune gene expression profile of Penaeus monodon in response to marine yeast glucan application and white spot syndrome virus challenge

Immunostimulant potential of eight marine yeast glucans (YG) from Candida parapsilosis R20, Hortaea werneckii R23, Candida spencermartinsiae R28, Candida haemulonii R63, Candida oceani R89, Debaryomyces fabryi R100, Debaryomyces nepalensis R305 and Meyerozyma guilliermondii R340 were tested against WSSV challenge in Penaeus monodon post larvae (PL). Structural characterization of these marine yeast glucans by proton nuclear magnetic resonance (NMR) indicated structures containing (1-6)-branched (1-3)-β-D-glucan. PL were fed 0.2% glucan incorporated diet once in seven days for a period of 45 days and the animals were challenged with white spot syndrome virus (WSSV). The immunostimulatory activity of yeast glucans were assessed pre- and post-challenge WSSV by analysing the expression profile of six antimicrobial peptide (AMP) genes viz., anti-lipopolysaccharide factor (ALF), crustin-1, crustin-2, crustin-3, penaeidin-3 and penaeidin-5 and 13 immune genes viz., alpha-2-macroglobulin (α-2-M), astakine, caspase, catalase, glutathione peroxidase, glutathione-s-transferase, haemocyanin, peroxinectin, pmCathepsinC, prophenol oxidase (proPO), Rab-7, superoxide dismutase and transglutaminase. Expression of seven WSSV genes viz., DNA polymerase, endonuclease, protein kinase, immediate early gene, latency related gene, thymidine kinase and VP28 were also analysed to detect the presence and intensity of viral infection in the experimental animals post-challenge. The study revealed that yeast glucans (YG) do possess immunostimulatory activity against WSSV and also supported higher survival (40–70 %) post-challenge WSSV. Among the various glucans tested, YG23 showed maximum survival (70.27%), followed by YG20 (66.66%), YG28 (60.97%), YG89 (58.53%), YG100 (54.05%), YG63 (48.64%), YG305 (45.7%) and YG340 (43.24%).

Mycological Characteristics of Nine Unrecorded Yeasts from Flowers in the Orchard of Yesan-gun, Chungcheongnam-do and Hanbat Arboretum in Daejeon City, Korea

Six unrecorded yeasts, Cryptococcus festucosus 41-3, Cryptococcus heveanensis 56-4, Debaryomyces nepalensis 95- 4, Issatchenkia occidentalis 142-1, Dioszegia zsoltii 39-1, and Kwoniella europala 47-2 were screened from 108 yeasts isolated from flowers and fruits in orchards of Yesan-gun, Chungcheongnam-do, Korea. The morphological and cultural characteristics of these unrecorded yeasts were investigated. They had various shapes, including ellipsoidal, globose, and oval, and also had budding mode in vegetable reproduction, except I. occidentalis 142-1 (fission mode). K. europaea 47-2 only formed pseudomy- celium. D. zsoliti 39-1 did not grow in yeast extract-malt extract medium, potato dextrose medium, and vitamin-free medium. C. festucosus 41-3 grew well in 5% NaCl-containing yeast extract-peptone-dextrose medium and had a growth pH range of 7.0~ 10.0. Three unrecorded yeasts Ogataea polymorpha HB45-1, Rhodotonula hinnulla HB62-2, and Cryptococcus rajasthanensis HB80-4 were screened from 51 yeasts isolated from flowers in Hanbat arboretum in Daejeon city, Korea. They were globose in shape and did not form pseudomycelium. In addition, O. polymorpha HB45-1 and C. rajasthanensis HB80-4 had budding mode in vegetable reproduction. All of them grew well in vitamin-free medium and C. rajasthanesis HB80-4 also grew in 50% glucose and 5% NaCl-containing YPD medium.

Diversity of culturable yeasts in phylloplane of sugarcane in Thailand and their capability to produce indole-3-acetic acid

Yeasts were isolated by the enrichment technique from the phylloplane of 94 samples of sugarcane leaf collected from seven provinces in Thailand. All sugarcane leaf samples contained yeasts and 158 yeast strains were obtained. On the basis of the D1/D2 domain of the large subunit rRNA gene sequence analysis, 144 strains were identified to 24 known species in 14 genera belonging to the Ascomycota viz. Candida akabanensis, Candida dendronema, Candida mesorugosa, Candida michaelii, Candida nivariensis, Candida rugosa, Candida orthopsilosis, Candida quercitrusa, Candida tropicalis, Candida xylopsoci, Cyberlindnera fabianii, Cyberlindnera rhodanensis, Debaryomyces nepalensis, Hannaella aff. coprosmaensis, Hanseniaspora guilliermondii, Kluyveromyces marxianus, Lachancea thermotolerans, Lodderomyces elongisporus, Metschnikowia koreensis, Meyerozyma caribbica, Millerozyma koratensis, Pichia kudriavzevii,Torulasporadelbrueckii and Wickerhamomyces edaphicus, and 12 species in six genera of the Basidiomycota viz . Cryptococcus flavescens, Cryptococcus laurentii, Cryptococcus rajasthanensis, Kwoniellaheveanensis, Rhodosporidium fluviale, Rhodosporidium paludigenum, Rhodotorula mucilaginosa, Rhodotorula sesimbrana, Rhodotorula taiwanensis, Sporidiobolus ruineniae, Sporobolomyces carnicolor and Sporobolomyces nylandii. Seven strains were identical or similar to four undescribed species. Another seven strains represented four novels species in the genus Metschnikowia, Nakazawaea, Wickerhamomyces and Yamadazyma. The results revealed 69% of the isolated strains were ascomycete yeastsand 31% were basidiomycete yeast. The most prevalent species was M. caribbica with a 23% frequency of occurrence followed by Rh. taiwanensis (11%) and C. tropicalis (10%). All strains were assessed for indole-3-acetic acid (IAA) producing capability showing that 69 strains had the capability of producing IAA when cultivated in yeast extract peptone dextrose broth supplemented with 1g/L L-tryptophan. The highest IAA concentration of 565.1mg/L was produced by R. fluviale DMKU-RK253.

Bioconversion of Non-Detoxified Hemicellulose Hydrolysates to Xylitol by Halotolerant Yeast Debaryomyces nepalensis NCYC 3413

Lignocellulosic materials are one of the most abundant renewable resources whose exploitation for the production of biochemicals and biofuels is the major challenge in the area of industrial biotechnology due to inhibition of growth and product formation by the toxic compounds released upon their hydrolysis. Indeed the bioprocess that can produce industrial products from hemicellulose hydrolysates in the presence of toxic compounds is economical than the process which involves detoxification. In this study, the ability of halotolerant strain Debaryomyces nepalensis NCYC 3413 to convert non-detoxified xylose enriched hemicellulose hydrolysates from corn cobs, rice straw, sugarcane bagasse and wheat straw to xylitol was evaluated. It was found that this strain has the capability to grow in all hemicellulose hydrolysates and convert xylose to xylitol without detoxification of hydrolysates. The maximum xylitol concentration of 14.6 g L-1 was obtained from corn cobs and wheat straw with productivities of 0.16 and 0.20 g L-1 h-1 respectively at a yield of 0.30 g g-1. Whereas sugarcane bagasse and rice straw gave xylitol yields of 0.31 and 0.32 g g-1 respectively with 14.2 g L-1 maximum xylitol and productivities were calculated to be 0.20 and 0.15 g L-1 h-1 respectively. The presence of high glucose hindered xylitol production by producing ethanol. Based on our findings, we suggest that (i) D. nepalensis is a promising strain for ecofriendly xylitol production as it exhibits broad specificity to lignocellulose substrates, fermentation of mixed sugars and (ii) tolerance towards lignocellulosic inhibitors making the process more economical.

Fermentable sugars recovery from grape stalks for bioethanol production

Three different processes were investigated for the recovery of fermentable sugars from grape stalks: autohydrolysis at 121 °C before and after a pre-washing step and acid hydrolysis (2% H2SO4w/w) after a pre-washing step. Moreover, optimal conditions of a charcoal-based purification process were determined by experimental design. All hydrolysates, with their corresponding synthetic liquors were used as fermentation substrates for the production of metabolites by the yeast: Debaryomyces nepalensis NCYC 1026. The main fermentation product was ethanol, where a maximum production of 20.84 g/l, a conversion yield of 0.35 g ethanol/g monomeric sugars and a productivity of 0.453 g/l h were obtained from non-purified autohydrolysate liquor. In all cases, ethanol production and cell growth were better in non-purified liquors than in synthetic liquors. These results could be influenced by the presence of other sugars in the hydrolysates, with higher concentration in non-purified ones.

Candida guilliermondii and Other Species of Candida Misidentified as Candida famata: Assessment by Vitek 2, DNA Sequencing Analysis, and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry in Two Global Antifungal Surveillance Programs

Candida famata (teleomorph Debaryomyces hansenii) has been described as a medically relevant yeast, and this species has been included in many commercial identification systems that are currently used in clinical laboratories. Among 53 strains collected during the SENTRY and ARTEMIS surveillance programs and previously identified as C. famata (includes all submitted strains with this identification) by a variety of commercial methods (Vitek, MicroScan, API, and AuxaColor), DNA sequencing methods demonstrated that 19 strains were C. guilliermondii, 14 were C. parapsilosis, 5 were C. lusitaniae, 4 were C. albicans, and 3 were C. tropicalis, and five isolates belonged to other Candida species (two C. fermentati and one each C. intermedia, C. pelliculosa, and Pichia fabianni). Additionally, three misidentified C. famata strains were correctly identified as Kodomaea ohmeri, Debaryomyces nepalensis, and Debaryomyces fabryi using intergenic transcribed spacer (ITS) and/or intergenic spacer (IGS) sequencing. The Vitek 2 system identified three isolates with high confidence to be C. famata and another 15 with low confidence between C. famata and C. guilliermondii or C. parapsilosis, displaying only 56.6% agreement with DNA sequencing results. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) results displayed 81.1% agreement with DNA sequencing. One strain each of C. metapsilosis, C. fermentati, and C. intermedia demonstrated a low score for identification (<2.0) in the MALDI Biotyper. K. ohmeri, D. nepalensis, and D. fabryi identified by DNA sequencing in this study were not in the current database for the MALDI Biotyper. These results suggest that the occurrence of C. famata in fungal infections is much lower than previously appreciated and that commercial systems do not produce accurate identifications except for the newly introduced MALDI-TOF instruments.

A Statistical Approach to Optimize Xylitol Production by &amp;lt;i&amp;gt;Debaryomyces nepalensis&amp;lt;/i&amp;gt; NCYC 3413 &amp;lt;i&amp;gt;in Vitro&amp;lt;/i&amp;gt;

Debaryomyces nepalensis NCYC 3413, halotolerant yeast isolated from rotten apple, was capable of utilizing components of hemicellulose hydrolysate such as glucose, galactose, mannose, xylose and arabinose. The organism utilizes xylose as a sole carbon source and produces xylitol. The Plackett-Burman design was applied to determine the specific medium components affecting xylitol production and found that xylose, K2HPO4, and ZnSO4 were critical in augmenting xylitol production. These significant parameters were further optimized using response surface methodology. The optimum concentrations of xylose, K2HPO4, and ZnSO4 were found to be 100 g/l, 10.6 g/l and 8.9 mg/l respectively. Under these optimal conditions the xylitol production increased from 27 g/l to 36 g/l with a yield of 0.44 g/g (57% increase in total yield). In addition, formation of the by product (glycerol) was decreased under optimal conditions.

Purification and biochemical characterization of a moderately halotolerant NADPH dependent xylose reductase from Debaryomyces nepalensis NCYC 3413

A Xylose reductase (XR) from the halotolerant yeast, Debaryomyces nepalensis NCYC 3413 was purified to apparent homogeneity. The enzyme has a molecular mass of 74kDa with monomeric subunit of 36.4kDa (MALDI-TOF/MS) and pI of 6.0. The enzyme exhibited its maximum activity at pH 7.0 and 45°C (21.2U/mg). In situ gel digestion and peptide mass fingerprinting analysis showed 12–22% sequence homology with XR from other yeasts. Inhibition of the enzyme by DEPC (diethylpyrocarbonate) confirmed the presence of histidine residue in its active site. The enzyme exhibited high preference for pentoses over hexoses with greater catalytic efficiency for arabinose than xylose. The enzyme also showed absolute specificity with NADPH over NADH. The enzyme retained 90% activity with 100mM of NaCl or KCl and 40% activity with 1M KCl which suggest that the enzyme is moderately halotolerant and can be utilized for commercial production of xylitol under conditions where salts are present.

Erratum to: Metabolism of glucose and xylose as single and mixed feed in Debaryomyces nepalensis NCYC 3413: production of industrially important metabolites

Erratum to: Metabolism of glucose and xylose as single and mixed feed in Debaryomyces nepalensis NCYC 3413: production of industrially important metabolites

Metabolism of glucose and xylose as single and mixed feed in Debaryomyces nepalensis NCYC 3413: production of industrially important metabolites

Efficient conversion of hexose and pentose (glucose and xylose) by a single strain is a very important factor for the production of industrially important metabolites using lignocellulose as the substrate. The kinetics of growth and polyol production by Debaryomyces nepalensis NCYC 3413 was studied under single and mixed substrate conditions. In the presence of glucose, the strain produced ethanol (35.8 ± 2.3g/l), glycerol (9.0 ± 0.2g/l), and arabitol (6.3 ± 0.2g/l). In the presence of xylose, the strain produced xylitol (38 ± 1.8g/l) and glycerol (18 ± 1.0g/l) as major metabolites. Diauxic growth was observed when the strain was grown with different combinations of glucose/xylose, and glucose was the preferred substrate. The presence of glucose enhanced the conversion of xylose to xylitol. By feeding a mixture of glucose at 100g/l and xylose at 100g/l, it was found that the strain produced a maximum of 72 ± 3g/l of xylitol. A study of important enzymes involved in the synthesis of xylitol (xylose reductase (XR) and xylitol dehydrogenase (XDH)), glycerol (glycerol-3-phosphate dehydrogenase (G3PDH)) and ethanol (alcohol dehydrogenase (ADH)) in cells grown in the presence of glucose and xylose revealed high specific activity of G3PDH and ADH in cells grown in the presence of glucose, whereas high specific activity of XR, XDH, and G3PDH was observed in cells grown in the presence of xylose. To our knowledge, this is the first study to elaborate the glucose and xylose metabolic pathway in this yeast strain.

Fungal diversity associated with Brazilian energy transmission towers

The present work profiled the fungal community structure found in Brazilian energy transmission tower with signs of corrosion and/or biofilm formation using cloning (ITS-rRNA gene libraries) and culture-dependent technique. A total of 31 isolates comprising 10 filamentous fungi and 21 yeasts were recovered from enrichment cultures. As determined by polyphasic taxonomy 9 genera and 13 species were identified including Aspergillus fumigatus, Aspergillus niger, Candida albicans, Candida pseudointermedia, Candida tropicalis, Cryptococcus laurentii, Debaryomyces nepalensis, Exophiala dermatitidis, Fusarium sp., Fusarium solani, Paecilomyces lilacinus, Trichoderma citrinoviride, Trichoderma longibrachiatum, and Pichia guilliermondii. Metagenomic analyses based on 160 clone sequences revealed 30 operational taxonomic units (OTUs) comprising 20 OTUs of filamentous fungi and 10 OTUs of yeasts. The majority of OTUs were related to the genera Capnobotryella, Cryptococcus, Devriesia, Fellomyces, Fusarium, Kockovaella, Panaeolus, Rhodotorula, Sirobasidium, Sporobolomyces, Strelitziana and Teratosphaeria. Although members of the fungal community from transmission tower samples are ubiquitous fungi commonly found in other environments, some have been related to microbiologically-influenced corrosion of metals. Comparisons between fungal community composition obtained by both culture-dependent and independent methods highlighted the different aspects of the mycobiota, emphazising the need of complementary approaches to assess the microbial assemblage of unusual environments.