RESUMO
The yeast Cyberlindnera xylosilytica UFMG-CM-Y309 has been identified as a promising new xylitol producer from sugarcane bagasse hemicellulosic hydrolysate (SCHH). However, SCHH pretreatment process generates byproducts, which are toxic to cell metabolism, including furans, phenolic compounds, and carboxylic acids, such as acetic acid, typically released at high concentrations. This research aims to reduce acetic acid in sugarcane hemicellulose hydrolysate concomitantly with xylitol production by yeast strain Cy. xylosilytica UFMG-CM-Y309 in a bioreactor by strategically evaluating the influence of volumetric oxygen transfer coefficient (kLa) (21 and 35 h-1). Experiments were conducted on a bench bioreactor (2 L volumetric capacity) at different initial kLa values (21 and 35 h-1). SCHH medium was supplemented with rice bran extract (10 g L-1) and yeast extract (1 g L-1). Cy. xylosilytica showed high xylitol production performance (19.56 g L-1), xylitol yield (0.56 g g-1) and, maximum xylitol-specific production rate (µpmáx 0.20 gxylitol·g-1 h-1) at kLa value of 21 h-1, concomitantly slowing the rate of acetic acid consumption. A faster acetic acid consumption (100%) by Cy. xylosilytica was observed at kLa of 35 h-1, concomitantly with an increase in maximum cellular growth (14.60 g L-1) and reduction in maximum xylitol production (14.56 g L-1 and Yp/s 0.34 g g-1). This study contributes to pioneering research regarding this yeast performance in bioreactors, emphasizing culture medium detoxification and xylitol production.
Assuntos
Celulose , Saccharum , Celulose/metabolismo , Xilitol , Ácido Acético/metabolismo , Hidrólise , Reatores Biológicos , Leveduras/metabolismo , FermentaçãoRESUMO
The learning process for a Biology topic regarding organisms and animal kingdom diversity was investigated through an innovative Interactive Didactic Sequence (IDS) which integrated the idea of "concept maps" with the Hermeneutic-Dialectic Circle (HDC). HDC is a tool for data collection and a reference for pluralist-constructivist thinking, considered a form of fourth-generation evaluation. Hofstede's cultural dimensions were also integrated into the investigation in order to facilitate mediation in an evaluative context. Students' performances (Nâ¯=â¯25) from a São Paulo-Brazil public school were statistically evaluated. Their cultural profile was determined via the Hofstede Value Survey Model 1994 questionnaire. The elaborative process of arranging concept maps was individual (CM-individual) and integrated with HDC in groups (CM-HDC). Concept map assessment methods were based off existing literature. An improvement in students' performances (pâ¯<â¯0.05) that presented concept maps integrated to HDC in a more complex structure when compared to individually-built maps was observed. Employment of HDC helped form motivational/interactive dialogues between students and teachers, which, in turn, assisted in achieving greater learning through the use of concept maps. The application of the fourth-generation evaluation was improved via knowledge regarding students' cultural profiles.
Assuntos
Aprendizagem , Instituições Acadêmicas , Brasil , Avaliação de Programas e Projetos de Saúde , BiologiaRESUMO
This study investigated the diversity of yeast species associated with rotting wood in Brazilian Amazonian rainforests. A total of 569 yeast strains were isolated from rotting wood samples collected in three Amazonian areas (Universidade Federal do Amazonas-Universidade Federal do Amazonas [UFAM], Piquiá, and Carú) in the municipality of Itacoatiara, Amazon state. The samples were cultured in yeast nitrogen base (YNB)-d-xylose, YNB-xylan, and sugarcane bagasse and corncob hemicellulosic hydrolysates (undiluted and diluted 1:2 and 1:5). Sugiyamaella was the most prevalent genus identified in this work, followed by Kazachstania. The most frequently isolated yeast species were Schwanniomyces polymorphus, Scheffersomyces amazonensis, and Wickerhamomyces sp., respectively. The alpha diversity analyses showed that the dryland forest of UFAM was the most diverse area, while the floodplain forest of Carú was the least. Additionally, the difference in diversity between UFAM and Carú was the highest among the comparisons. Thirty candidates for new yeast species were obtained, representing 36% of the species identified and totaling 101 isolates. Among them were species belonging to the clades Spathaspora, Scheffersomyces, and Sugiyamaella, which are recognized as genera with natural xylose-fermenting yeasts that are often studied for biotechnological and ecological purposes. The results of this work showed that rotting wood collected from the Amazonian rainforest is a tremendous source of diverse yeasts, including candidates for new species.
Assuntos
Saccharum , Madeira , Celulose , Floresta Úmida , Brasil , Filogenia , LevedurasRESUMO
BACKGROUND: This study is the first to investigate the Brazilian Amazonian Forest to identify new D-xylose-fermenting yeasts that might potentially be used in the production of ethanol from sugarcane bagasse hemicellulosic hydrolysates. METHODOLOGY/PRINCIPAL FINDINGS: A total of 224 yeast strains were isolated from rotting wood samples collected in two Amazonian forest reserve sites. These samples were cultured in yeast nitrogen base (YNB)-D-xylose or YNB-xylan media. Candida tropicalis, Asterotremella humicola, Candida boidinii and Debaryomyces hansenii were the most frequently isolated yeasts. Among D-xylose-fermenting yeasts, six strains of Spathaspora passalidarum, two of Scheffersomyces stipitis, and representatives of five new species were identified. The new species included Candida amazonensis of the Scheffersomyces clade and Spathaspora sp. 1, Spathaspora sp. 2, Spathaspora sp. 3, and Candida sp. 1 of the Spathaspora clade. In fermentation assays using D-xylose (50 g/L) culture medium, S. passalidarum strains showed the highest ethanol yields (0.31 g/g to 0.37 g/g) and productivities (0.62 g/L · h to 0.75 g/L · h). Candida amazonensis exhibited a virtually complete D-xylose consumption and the highest xylitol yields (0.55 g/g to 0.59 g/g), with concentrations up to 25.2 g/L. The new Spathaspora species produced ethanol and/or xylitol in different concentrations as the main fermentation products. In sugarcane bagasse hemicellulosic fermentation assays, S. stipitis UFMG-XMD-15.2 generated the highest ethanol yield (0.34 g/g) and productivity (0.2 g/L · h), while the new species Spathaspora sp. 1 UFMG-XMD-16.2 and Spathaspora sp. 2 UFMG-XMD-23.2 were very good xylitol producers. CONCLUSIONS/SIGNIFICANCE: This study demonstrates the promise of using new D-xylose-fermenting yeast strains from the Brazilian Amazonian Forest for ethanol or xylitol production from sugarcane bagasse hemicellulosic hydrolysates.
Assuntos
Variação Genética , Árvores/microbiologia , Xilose/metabolismo , Leveduras/genética , Leveduras/metabolismo , Brasil , Celulose/metabolismo , Primers do DNA/genética , Etanol/metabolismo , Fermentação , Reação em Cadeia da Polimerase , Especificidade da Espécie , Xilitol/biossínteseRESUMO
Response surface methodology (RSM), based on a 2(2) full factorial design, evaluated the moisture effects in recovering xylose by diethyloxalate (DEO) hydrolysis. Experiments were carried out in laboratory reactors (10 mL glass ampoules) containing corn stover (0.5 g) properly ground. The ampoules were kept at 160 °C for 90 min. Both DEO concentration and corn stover moisture content were statistically significant at 99% confidence level. The maximum xylose recovery by the response surface methodology was achieved employing both DEO concentration and corn stover moisture at near their highest levels area. We amplified this area by using an overlay plot as a graphical optimization using a response of xylose recovery more than 80%. The mathematical statistical model was validated by testing a specific condition in the satisfied overlay plot area. Experimentally, a maximum xylose recovery (81.2%) was achieved by using initial corn stover moisture of 60% and a DEO concentration of 4% w/w. The mathematical statistical model showed that xylose recovery increases during DEO corn stover acid hydrolysis as the corn stover moisture level increases. This observation could be important during the harvesting of corn before it is fully dried in the field. The corn stover moisture was an important variable to improve xylose recovery by DEO acid hydrolysis.
Assuntos
Oxalatos/química , Xilose/isolamento & purificação , Zea mays/química , Hidrólise , Modelos Químicos , Água/análiseRESUMO
Corn stover that had been treated with vapor-phase diethyl oxalate released a mixture of mono- and oligosaccharides consisting mainly of xylose and glucose. Following overliming and neutralization, a D-xylulokinase mutant of Pichia stipitis, FPL-YS30 (xyl3-∆1), converted the stover hydrolysate into xylitol. This research examined the effects of phosphoric or gluconic acids used for neutralization and urea or ammonium sulfate used as nitrogen sources. Phosphoric acid improved color and removal of phenolic compounds. D-Gluconic acid enhanced cell growth. Ammonium sulfate increased cell yield and maximum specific cell growth rate independently of the acid used for neutralization. The highest xylitol yield (0.61 g(xylitol)/g(xylose)) and volumetric productivity (0.18 g(xylitol)/g(xylose )l) were obtained in hydrolysate neutralized with phosphoric acid. However, when urea was the nitrogen source the cell yield was less than half of that obtained with ammonium sulfate.
Assuntos
Pichia/enzimologia , Xilitol/biossíntese , Zea mays , Sulfato de Amônio/química , Fermentação , Gluconatos/química , Ácidos Fosfóricos/química , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Pichia/crescimento & desenvolvimento , Xilose/metabolismoRESUMO
Spent sulfite pulping liquor (SSL) contains lignin, which is present as lignosulfonate, and hemicelluloses that are present as hydrolyzed carbohydrates. To reduce the biological oxygen demand of SSL associated with dissolved sugars, we studied the capacity of Pichia stipitis FPL-YS30 (xyl3Delta) to convert these sugars into useful products. FPL-YS30 produces a negligible amount of ethanol while converting xylose into xylitol. This work describes the xylose fermentation kinetics of yeast strain P.stipitis FPL-YS30. Yeast was grown in rich medium supplemented with different carbon sources: glucose, xylose, or ammonia-base SSL. The SSL and glucose-acclimatized cells showed similar maximum specific growth rates (0.146 h(-1)). The highest xylose consumption at the beginning of the fermentation process occurred using cells precultivated in xylose, which showed relatively high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49). However, the maximum specific rates of xylose consumption (0.19 g(xylose)/g(cel) h) and xylitol production (0.059 g(xylitol)/g(cel) h) were obtained with cells acclimatized in glucose, in which the ratio between xylose reductase (EC 1.1.1.21) and xylitol dehydrogenase (EC 1.1.1.9) was kept at higher level (0.82). In this case, xylitol production (31.6 g/l) was 19 and 8% higher than in SSL and xylose-acclimatized cells, respectively. Maximum glycerol (6.26 g/l) and arabitol (0.206 g/l) production were obtained using SSL and xylose-acclimatized cells, respectively. The medium composition used for the yeast precultivation directly reflected their xylose fermentation performance. The SSL could be used as a carbon source for cell production. However, the inoculum condition to obtain a high cell concentration in SSL needs to be optimized.
Assuntos
Modelos Biológicos , Papel , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Pichia/enzimologia , Pichia/genética , Sulfitos/metabolismo , Xilitol/metabolismo , Xilose/metabolismo , Técnicas de Cultura de Células/métodos , Simulação por Computador , Fermentação , Resíduos Industriais/prevenção & controle , Cinética , Taxa de Depuração Metabólica , Mutação , Fosfotransferases (Aceptor do Grupo Álcool)/genéticaRESUMO
OBJECTIVE: We evaluated the practice of nutritional therapy (NT) by NT multiprofessional teams (NTMTs) in hospitals of the São Paulo metropolitan region to verify its adequacy in meeting the legislation that regulates NT in Brazil. METHODS: This was an open prospective study using active research through an inquiry with a multiple-choice, directed, and descriptive questionnaire, which was evaluated using EPI Info 6.04. Data were presented as median and 25th and 75th percentiles and compared according to the considered outcome. P < 0.05 was considered statistically significant. RESULTS: Of 119 evaluated hospitals in the São Paulo metropolitan region, 84 were located in the city itself and 35 in the surrounding cities. There were 52 hospitals with NTMTs: 35 in the city of São Paulo and 13 in the other cities. No significant statistical differences were found when comparing the hospitals according to size (small, average, large, and specialized) and to the presence of a NTMT. We observed that the philanthropic institutions presented a significantly higher frequency of NTMTs presence. The private, academic, and public hospitals did not present significant differences with regard to the presence of NTMTs. CONCLUSION: The number of NTMTs in the hospitals of the São Paulo metropolitan area is below the requirement established by law; the existence of a NTMT is more frequent in medium and large hospitals; the purchase of the necessary supplies and equipment for the NT practice is more adequate in hospitals with non-public reimbursement; the NTMTs in non-public hospitals were found to be more competent than those in public hospitals in implementing enteral and parenteral nutrition; private hospitals offer better conditions for professional growth for a NTMT staff compared with public hospitals.
Assuntos
Atenção à Saúde/normas , Hospitais Privados/normas , Hospitais Públicos/normas , Apoio Nutricional/normas , Equipe de Assistência ao Paciente , Brasil , Fidelidade a Diretrizes , Número de Leitos em Hospital , Hospitais Privados/estatística & dados numéricos , Hospitais Públicos/estatística & dados numéricos , Humanos , Reembolso de Seguro de Saúde , Estudos Prospectivos , Inquéritos e QuestionáriosRESUMO
The present work evaluated the key enzymes involved in xylitol production (xylose reductase [XR] and xylitol dehydrogenase [XDH]) and their correlation with xylose, arabinose, and acetic acid assimilation during cultivation of Candida guilliermondii FTI 20037 cells in sugarcane bagasse hemicellulosic hydrolysate. For this purpose, inocula previously grown either in sugarcane bagasse hemicellulosic hydrolysate (SBHH) or in semidefined medium (xylose as a substrate) were used. The highest xylose/acetic acid consumption ratio (1.78) and the lowest arabinose consumption (13%) were attained in the fermentation using inoculum previously grown in semidefined medium (without acetic acid and arabinose). In this case, the highest values of XR (1.37 U mg prot(-1)) and XDH (0.91 U mg prot(-1)) activities were observed. The highest xylitol yield (approximately 0.55 g g(-1)) and byproducts (ethanol and glycerol) formation were not influenced by inoculum procedure. However, the cell previously grown in the hydrolysate was effective in enhancing xylitol production by keeping the XR enzyme activity at high levels (around 0.99 U.mg(prot) (-1)), reducing the XDH activity (34.0%) and increasing xylitol volumetric productivity (26.5%) with respect to the inoculum cultivated in semidefined medium. Therefore, inoculum adaptation to SBHH was shown to be an important strategy to improve xylitol productivity.