Role of Glycerol Addition on Xylose-to-Xylitol Bioconversion by Candida guilliermondii

The effect of glycerol on xylose-to-xylitol bioconversion by Candida guilliermondii was evaluated by its addition (0.7 and 6.5 g/l) to semidefined media (xylose as a substrate). The glycerol concentrations were chosen based on the amounts produced during previous studies on xylitol production by C. guilliermondii. Medium without glycerol addition (control) and medium containing glycerol (53 g/l) in substitution to xylose were also evaluated. According to the results, the addition of 0.7 g/l glycerol to the fermentation medium favored not only the yield (Y (P/S) = 0.78 g/g) but also the xylitol productivity (Q (P) = 1.13 g/l/h). During the xylose-to-xylitol bioconversion, the formation of byproducts (glycerol and ethanol) was observed for all conditions employed. In relation to the cellular growth, glycerol as the only carbon source for C. guilliermondii was better than xylose or xylose and glycerol mixtures, resulting in a maximum cellular concentration (5.34 g/l).

Evaluation of hexose and pentose in pre-cultivation of Candida guilliermondii on the key enzymes for xylitol production in sugarcane hemicellulosic hydrolysate

The evaluation of hexose and pentose in pre-cultivation of Candida guilliermondii FTI 20037 yeast on xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes activities was performed during fermentation in sugarcane bagasse hemicellulosic hydrolysate. The xylitol production was evaluated by using cells previously growth in 30.0 gl(-1) xylose, 30.0 gl(-1) glucose and in both sugars mixture (30.0 gl(-1) xylose and 2.0 gl(-1) glucose). The vacuum evaporated hydrolysate (80 gl(-1)) was detoxificated by ion exchange resin (A-860S; A500PS and C-150-Purolite(A (R))). The total phenolic compounds and acetic acid were 93.0 and 64.9%, respectively, removed by the resin hydrolysate treatment. All experiments were carried out in Erlenmeyer flasks at 200 rpm, 30A degrees C. The maximum XR (0.618 Umg (Prot) (-1) ) and XDH (0.783 Umg (Prot) (-1) ) enzymes activities was obtained using inoculum previously growth in both sugars mixture. The highest cell concentration (10.6 gl(-1)) was obtained with inoculum pre-cultivated in the glucose. However, the xylitol yield and xylitol volumetric productivity were favored using the xylose as carbon source. In this case, it was observed maximum xylose (81%) and acetic acid (100%) consumption. It is very important to point out that maximum enzymatic activities were obtained when the mixture of sugars was used as carbon source of inoculum, while the highest fermentative parameters were obtained when xylose was used.

Establishment of the optimum initial xylose concentration and nutritional supplementation of brewer`s spent grain hydrolysate for xylitol production by Candida guilliermondii

The effects of initial xylose concentration and nutritional supplementation of brewer`s spent grain hydrolysate on xylitol production by Candida guilliermondii were evaluated using experimental design methodology. The hydrolysate containing 55, 75 or 95 g/l xylose, supplemented or not with nutrients (calcium chloride, ammonium sulfate and rice bran extract), was used as fermentation medium. The increase in xylitol yield and productivity was related to the increase of initial xylose concentration, but up to a certain limit. above of which the yeast performance was not improved. The hydrolysate supplementation with nutrients did not interfere with xylose-to-xylitol conversion. By using the statistic tool the best conditions for maximum xylitol production were found. which consisted in using the non-supplemented hydrolysate containing 70 g/l initial xylose concentration. Under these conditions, a xylitol yield of 0.78 g/g and productivity of 0.58 g/(l h) were achieved. (C) 2008 Elsevier Ltd. All rights reserved.

Inhibitory action of toxic compounds present in lignocellulosic hydrolysates on xylose to xylitol bioconversion by Candida guilliermondii

The inhibitory action of acetic acid, ferulic acid, and syringaldehyde on metabolism of Candida guilliermondii yeast during xylose to xylitol bioconversion was evaluated. Assays were performed in buffered and nonbuffered semidefined medium containing xylose as main sugar (80.0 g/l), supplemented or not with acetic acid (0.8-2.6 g/l), ferulic acid (0.2-0.6 g/l), and/or syringaldehyde (0.3-0.8 g/l), according to a 2(3) full factorial design. Since only individual effects of the variables were observed, assays were performed in a next step in semidefined medium containing different concentrations of each toxic compound individually, for better understanding of their maximum concentration that can be present in the fermentation medium without affecting yeast metabolism. It was concluded that acetic acid, ferulic acid, and syringaldehyde are compounds that may affect Candida guilliermondii metabolism (mainly cell growth) during bioconversion of xylose to xylitol. Such results are of interest and reveal that complete removal of toxic compounds from the fermentation medium is not necessary to obtain efficient conversion of xylose to xylitol by Candida guilliermondii. Fermentation in buffered medium was also considered as an alternative to overcome the inhibition caused by these toxic compounds, mainly by acetic acid.

PVA-Hydrogel Entrapped Candida Guilliermondii for Xylitol Production from Sugarcane Hemicellulose Hydrolysate

Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing-thawing method. Entrapment experiments were planned according to a 2(3) full factorial design, using the PVA concentration (80, 100, and 120 g L(-1)), the freezing temperature (-10, -15, and -20 degrees C), and the number of freezing-thawing cycles (one, three, and five) as the independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the same bioconversion in a stirred tank reactor operated at 400 rpm, 30 degrees C, and 1.04 vvm air flowrate. At the end of fermentation, a maximum xylitol concentration of 28.7 g L(-1), a xylitol yield on consumed xylose of 0.49 g g(-1) and a xylitol volumetric productivity of 0.24 g L(-1) h(-1) were obtained.

The behavior of key enzymes of xylose metabolism on the xylitol production by Candida guilliermondii grown in hemicellulosic hydrolysate

A variety of raw materials have been used in fermentation process. This study shows the use of rice straw hemicellulosic hydrolysate, as the only source of nutrient, to produce high added-value products. In the present work, the activity of the enzymes xylose reductase (XR); xylitol dehydrogenase (XD); and glucose-6-phosphate dehydrogenase (G6PD) during cultivation of Candida guilliermondii on rice straw hemicellulosic hydrolysate was measured and correlated with xylitol production under different pH values (around 4.5 and 7.5) and initial xylose concentration (around 30 and 70 g l(-1)). Independent of the pH value and xylose concentration evaluated, the title of XD remained constant. On the other hand, the volumetric activity of G6PD increased whereas the level of XR decreased when the initial xylose concentration was increased from 30 to 70 g l(-1). The highest values of xylitol productivity (Q (P) a parts per thousand 0.40 g l(-1)) and yield factor (Y (P/S) a parts per thousand 0.60 g g(-1)) were reached at highest G6PD/XR ratio and lowest XR/XD ratio. These results suggest that NADPH concentrations influence the formation of xylitol more than the activity ratios of the enzymes XR and XD. Thus, an optimal rate between G6PD and XR must be reached in order to optimize the xylitol production.

Candida guilliermondii as the aetiology of candidosis

Candida guilliermondii is one of the components of human microbiota. This yeast has been infrequently associated with human infections, which may be related to its low pathogenicity. The aim of this study was to provide clinical and epidemiological data for patients infected with C. guilliermondii at Santa Casa Complexo Hospitalar, Brazil. From October 1997 to October 2003, C. guilliermondii was isolated from clinical samples from 11 patients. Three patients were excluded because the isolation of the yeast represented colonisation. Specimens from the eight patients included in the study corresponded to blood (n = 5), ascitis fluid (n = 2), and oesophagus biopsy (n = 1). Three patients (37.5%) had major immunosuppressed conditions, including solid organ transplantation, AIDS, and leukaemia. Previous use of antibiotics occurred in 87.5%. Main invasive medical procedures were central venous catheter (50.0%), abdominal surgery (25.0%), and peritoneal dialysis (50.0%). No susceptibility data was obtained. Although risk factors for candidaemia were similar amongst patients infected by with C. guilliermondii or other Candida species, mortality associated with C. guilliermondii was significantly lower.

Aproveitamento de subproduto industrial de óleos vegetais para produção de riboflavina por Candida guilliermondii DM 644

A produção e consumo de alimentos industrializados têm aumentado a preocupação com suplementação e enriquecimento de alimentos com vitaminas e sais minerais, visando repor as possíveis perdas durante os processos de fabricação, principalmente das vitaminas hidrossolúveis, mais especificamente da vitamina B2 ou riboflavina. Assim sendo, a proposta deste trabalho foi utilizar como componente principal do meio, para produção da riboflavina, um subproduto do refino de óleos vegetais e o microrganismo Candida guillermondii DM 644. A produção da vitamina B2 foi realizada por fermentação em batelada utilizando Erlenmeyer. As condições empregadas foram agitação orbital, ausência de luz, 30°C, e 24h de incubação. A otimização da produção de riboflavina foi realizada através de Delineamento Fatorial Fracionário, para avaliar os efeitos da concentração de matéria graxa, fonte de nitrogênio, pH, velocidade de agitação, fonte de fósforo e extrato de levedura e as possíveis interações. A concentração máxima de riboflavina foi 19,12mg/mL. Os fatores mais importantes para produção de riboflavina foram a concentração de matéria graxa e a fonte de nitrogênio, enquanto que a fonte de fósforo e o extrato de leveduras não estimularam sua biossíntese. A máxima produção foi obtida com matéria graxa a 10g/L, uréia a 2,5g/L e pH 5,0. A velocidade de agitação (200 e 400rpm) não interferiu no processo biotecnológico.

Purification of Candida guilliermondii and Pichia ohmeri killer toxin as an active agent against Penicillium expansum

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CTAB, Triton X-100 and freezing-thawing treatments of Candida guilliermondii: Effects on permeability and accessibility of the glucose-6-phosphate dehydrogenase, xylose reductase and xylitol dehydrogenase enzymes

Cells of Candida guilliermondii (ATCC 201935) were permeabilised with surfactant treatment (CTAB or Triton X-100) or a freezing-thawing procedure. Treatments were monitored by in situ activities of the key enzymes involved in xylose metabolism, that is, glucose-6-phosphate dehydrogenase (G6PD), xylose reductase (XR) and xylitol dehydrogenase (XD). The permeabilising ability of the surfactants was dependent on its concentration and incubation time. The optimum operation conditions for the permeabilisation of C. guilliermondii with surfactants were 0.41 mM (CTAB) or 2.78 mM (Triton X-100), 30 degrees C, and pH 7 at 200 rpm for 50 min. The maximum permeabilisation measured in terms of the in situ G6PD activity observed was, in order, as follows: CTAB (122.4 +/- 15.7 U/g(cells)) > freezing-thawing, , (54.3 +/- 1.9 U/g(cells)) > Triton X-100 (23.5 +/- 0.0 U/g(cells)). These results suggest that CTAB surfactant is more effective in the permeabilisation of C. guilliermondii cells in comparison to the freezing-thawing and Triton X-100 treatments. Nevertheless, freezing-thawing was the only treatment that allowed measurable in situ XR activity. Therefore, freezing-thawing permeabilised yeast cells could be used as a source of xylose reductase for analytical purposes or for use in biotransformation process such as xylitol preparation from xylose. The level of in situ xylose reductase was found to be 13.2 +/- 0.1 U/g(cells).

Aspectos micológicos e suscetibilidade in vitro de leveduras do gênero Candida em pacientes HIV-positivos provenientes do Estado de Mato Grosso

INTRODUÇÃO: A candidíase é uma das infecções fúngicas mais frequentes entre os pacientes infectados pelo vírus da imunodeficiência humana. O presente estudo objetivou a caracterização das leveduras do gênero Candida de distintas amostras clínicas, provenientes de pacientes HIV - positivos, assim como a determinação do perfil de suscetibilidade in vitro a cinco drogas antifúngicas. MÉTODOS: A caracterização dos isolados de Candida sp foi realizada através da metodologia clássica, testes bioquímicos (zimograma e auxanograma) e morfológicos (prova do tubo germinativo e microcultivo em lâmina). Também, foram realizadas a técnica genotípica (PCR) e identificação pelo método comercial API 20C AUX (BioMeriéux). Para a determinação do perfil de suscetibilidade in vitro, foram utilizadas cinco drogas antifúngicas (cetoconazol, fluconazol, itraconazol, voriconazol e anfotericina B), através do método comercialmente disponível - Etest. RESULTADOS: Foram identificados 105 isolados de leveduras do gênero Candida provenientes de 102 pacientes infectados pelo vírus HIV. Destes, foram caracterizadas 82 (78,1%) Candida albicans, 8 (7,6%) Candida parapsilosis, 8 (7,6%) Candida tropicalis, 4 (3,8%) Candida krusei, 2 (1,9%) Candida glabrata e 1 (1%) Candida guilliermondii. CONCLUSÕES: Considerando o perfil geral de sensibilidade, 60% dos isolados foram suscetíveis a todos os antifúngicos testados, porém as espécies C. tropicalis e C. krusei demonstraram uma tendência a valores mais elevados de CIMs para os azóis do que os encontrados paraC. albicans, sugerindo resistência.

Phylogeny and evolution of the aspartyl protease family from clinically relevant Candida species

Aspartyl proteases are a class of enzymes that include the yeast aspartyl proteases and secreted aspartyl protease (Sap) superfamilies. Several Sap superfamily members have been demonstrated or suggested as virulence factors in opportunistic pathogens of the genus Candida. Candida albicans, Candida tropicalis, Candida dubliniensis and Candida parapsilosis harbour 10, four, eight and three SAP genes, respectively. In this work, genome mining and phylogenetic analyses revealed the presence of new members of the Sap superfamily in C. tropicalis (8), Candida guilliermondii (8), C. parapsilosis(11) and Candida lusitaniae (3). A total of 12 Sap families, containing proteins with at least 50% similarity, were discovered in opportunistic, pathogenic Candida spp. In several Sap families, at least two subfamilies or orthologous groups were identified, each defined by > 90% sequence similitude, functional similarity and synteny among its members. No new members of previously described Sap families were found in a Candida spp. clinical strain collection; however, the universality of SAPT gene distribution among C. tropicalis strains was demonstrated. In addition, several features of opportunistic pathogenic Candida species, such as gene duplications and inversions, similitude, synteny, putative transcription factor binding sites and genome traits of SAP gene superfamily were described in a molecular evolutionary context.

Xylitol from rice husks by acid hydrolysis and Candida yeast fermentation

An investigation was conducted into the production of xylose by acid hydrolysis of rice husks and its subsequent bioconversion to xylitol. The parameters were optimised using the response surface methodology. The fermentation stage took place with the aid of the yeast species Candida guilliermondii and Candida tropicalis. An evaluation of the influence of several biomass pre-treatments was also performed. The effects of the acid concentration and hydrolysate pH on xylitol global yield were also assessed, and the highest yield of xylitol was 64.0% (w/w). The main products, xylose and xylitol, were identified and quantified by means of liquid chromatography.

Avaliação da atividade biológica de óleos essenciais sobre candida não albicans de origem clínica

Candidíase é um problema de importância crescente, devido o aumento do número de indivíduos imunocomprometidos e o surgimento de cepas resistentes aos antifúngicos convencionais. É de fundamental importância a busca por novos agentes antifúngicos mais eficazes, menos tóxicos, sendo os óleos essenciais (OEs) excelentes alternativas para esse propósito. Esse estudo investigou a atividade biológica do OE de Mentha spicata L. sobre Candida guilliermondii de origem anal e vaginal. Para tanto foram determinadas a Concentração Inibitória Mínima (CIM), Concentração Fungicida Mínima (CFM), cinética do crescimento das leveduras (Time-Kill), alterações micromorfológicas (técnica do microcultivo em câmara úmida) e investigação do mecanismo de ação antifúngico, utilizando o bioensaio do sorbitol. O OE de M. spicata foi obtido pelo processo de extração por destilação a vapor. Na análise fitoquímica desse óleo foi observada a presença de carvona com 84,32%, seguida pelo limoneno (13,70%) e traços de iso-dihidrocarvona (0,82%). Os resultados da análise da CIM variou entre 32 e 128 μg/mL. A CFM variou entre 64 e 1024 μg/mL. Na avaliação da ação de OE e da nistatina 100UI/mL, o antifúngico padrão apresentou o efeito fungicida a partir de 4 horas e para OE de M. spicata foi observado efeito fungistático na CIM, CIMX2 e CIMX4 frente às cepas avaliadas. O OE de M. spicata apresentou forte atividade antifúngica contra as cepas de C. guilliermondii, promovendo alterações micromorfológicas visíveis por microscopia óptica, nas concentrações testadas (CIM, CIMx2), resultado semelhante ao que se observou com a nistatina (100UI/mL). Na investigação do mecanismo de ação antifúngico foi constatado que houve alteração da CIM na presença de sorbitol, com elevação dos valores quatro vezes maior que a concentração inicial, o que indica que os componentes desse OE apresentam ação direta sobre a parede celular das leveduras. Conclui-se que o OE de Mentha spicata é um potencial agente terapêutico no tratamento de candidíase

Hyaluronidase and chondroitin sulphatase production by different species of Candida

The production of hyaluronidase and chondroitin sulphatase by Candida albicans, Candida tropicalis, Candida parapsilosis, Candida guilliermondii and Candida krusei was investigated using a complex culture medium (Sabouraud glucose agar) and a chemically defined medium. Among the 63 C. albicans isolates tested, 61 (97.8%) were found to be hyaluronidase and chondroitin sulphatase producers; one isolate produced only chondroitin sulphatase and one other was unable to produce either enzyme. The second major hyaluronidase and chondroitin sulphatase producing species was C. tropicalis followed by C. guilliermondii, C. parapsilosis and C. krusei. Among the C. albicans isolates tested no relation between the source of isolation and the amount of hyaluronidase and chondroitin sulphatase produced was found.