Nitrogen source and pH interact and modulate lipase secretion in a non-clinical strain of Candida parapsilosis

Lipases (E.C. 3.1.1.3) are serine-hydrolases, and act on long chain fatty acid ester bonds. They exhibit specific and enantioselective activities, which are desirable for many industrial applications. This study aimed at screening and optimizing the production of lipases by wild yeast strains from a variety of substrates, as well as characterizing the enzyme. An initial selection was made in oxygenated oil-supplemented minimum medium, and the enzymatic activity of the supernatant was tested over p-nitrophenyl palmitate. One-hundred and twenty-four yeast strains from different substrates were tested, and twenty-three showed significantly higher lipolytic activity (p<0.01). One yeast in particular, QU110, showed best lipase production and therefore was selected for the optimization and characterization processes. This yeast exhibits enzyme secretion in initial pH 6.0, with olive oil and tryptone as carbon and nitrogen sources, respectively. There was a strong interaction between nitrogen source and initial pH, and pH 9.0seems to inhibit enzyme secretion. The crude enzyme (cell-free supernatant) shows stability in surfactants and n-hexane, but not in ethanol or methanol. A Response Surface Model was created and optimal enzyme activity conditions were observed at 36°C and pH 8.0. The lipase is appropriate for transesterification reactions, as the enzyme is more stable in strong apolar solvents than moderately apolar ones. Also, secretion by pH was not reported elsewhere, which should be further investigated and contribute for other yeast bioprocesses as well.

Funcionamento Diferencial de Itens (DIF) e experiência de afeto: questões de gênero / Differential Item Functioning and affect: gender issues

O presente estudo teve por objetivo contemplar o critério de justiça dos itens da Escala de Afeto Positivo e Afeto Negativo (PANAS), considerando contribuições das últimas décadas sobre a evidência de diferenças de gênero na manifestação dos traços em questão. Com esse objetivo, a PANAS foi aplicada em 354 participantes, de ambos os sexos. Os dados foram avaliados sob o paradigma da TRI, segundo o modelo para itens politômicos sugerido por Andrich (1988), e o critério de justiça de acordo com o Funcionamento Diferencial de Itens, conforme os parâmetros sugeridos por Linacre (2011), comparando amostras com sujeitos do sexo feminino e masculino. As evidências do presente estudo apontam para itens que favorecem determinadas características dos grupos em questão.

This article is an investigation into the justice criterion for the items of the Positive Affect and Negative Affect Schedule (PANAS) considering contributions from the last decades on gender differences as to emotion and affect experience. For this purpose, the PANAS was administered to 354 participants of both genders. Data was evaluated under the paradigm of IRT, according to the model of polytomous responses suggested by Andrich (1988), and the criterion of justice in accordance with the Differential Item Functioning on the parameters suggested by Linacre (2011) comparing male and female samples. Evidence indicates differential item functioning for specific items, favoring groups according to their characteristics.

Decomposição, liberação e volatilização de nitrogênio em resíduos culturais de mucuna-cinza (Mucuna cinerea) / Decomposition, release and volatilization of nitrogen from velvet bean (Mucuna cinerea) residues

As leguminosas possibilitam a incorporação biológica de nitrogênio aos sistemas de produção. Contudo, existe pouco conhecimento sobre a decomposição, liberação e volatilização de nitrogênioassociados à diferentes doses de seus resíduos. Objetivouse, neste trabalho avaliar a decomposição, a liberação e a volatilização de nitrogênio de diferentes doses de mucuna-cinza (Mucuna cinerea Piper & Tracy). O experimento constou de tratamentos com 12 (C12) ou 25 (C25) Mg ha-1 de composto orgânico: C12AV0 (sem leguminosa); C12AV4 (4 Mg ha-1 de resíduo); C12AV8 (8 Mg ha-1); C12AV12 (12 Mg ha-1); C25; AV12 (12 Mg ha-1) e testemunha absoluta. Adotou-se o delineamento de blocos casualizados e cinco repetições. Foram determinadas as taxas de decomposição do adubo verde e liberação de N, o teor de N-mineral no solo e a volatilização de N-NH3. A liberação de N (t½=28 dias) foi mais rápida que a decomposição do resíduo (t½=38 dias). Essa liberação de N eleva rapidamente os teores de N-mineral do solo e resulta também em maior elevação da volatilização de N-NH3. O incremento das doses de 8 para 12 Mg ha-1 de mucuna resultou em aumento mais que proporcional da volatilização acumulada de N-NH3, atingindo 30 kg ha-1 após 30 dias.

The use of leguminous species allows the biological incorporation of nitrogen into cropping systems. Nevertheless, there is little knowledge about the decomposition, release and volatilization of nitrogen associated with the decomposition of different quantities of residues. The objective of this study was to evaluate the decomposition of the biomass, the release and volatilization of nitrogen from different doses of velvet bean (Mucuna cinerea Piper & Tracy) residues. The treatments were established either with 12 (C12) or 25 (C25) Mg ha-1 of organic compost: C12AV0 (without residue); C12AV4 (4 Mg ha-1 of residue); C12AV8 (8 Mg ha-1); C12AV12 (12 Mg ha-1); C25; AV12 (12 Mg ha-1) and a control. The randomized block design was adopted with five repetitions. Mass dry matter decomposition and N release rate, the soil N-mineral content and N-NH3 volatilization were determined. N mineralization (t ½= 28 days) was faster than the decomposition of dry matter (t ½=38 days). This mineralization rapidly increased the soil mineral-N content and resulted in higher N-NH3 volatilization. However, the increase from 8 to 12 Mg ha-1 of velvet bean mass resulted in an overproportional increase of N-NH3 volatilization, which reached 30 kg ha-1 after 30 days.