ABSTRACT Blastocystis sp. is a common intestinal microorganism. The α-L-fucosidase (ALFuc) is an enzyme long associated with the colonization of the gut microbiota. However, this enzyme has not been experimentally identified in Blastocystis cultures. The objective of the present study was to identify ALFuc in supernatants of axenic cultures of Blastocystis subtype (ST)1 ATCC-50177 and ATCC-50610 and to compare predicted ALFuc proteins of alfuc genes in sequenced STs1–3 isolates in human Blastocystis carriers. Excretion/secretion (Es/p) and cell lysate proteins were obtained by processing Blastocystis ATCC cultures and submitting them to SDS–PAGE and immunoblotting. In addition, 18 fecal samples from symptomatic Blastocystis human carriers were analyzed by sequencing of amplification products for subtyping. A complete identification of the alfuc gene and phylogenetic analysis were performed. Immunoblotting showed that the amplified band corresponding to ALFuc (~51 kDa) was recognized only in the ES/p. Furthermore, prediction analysis of ALFuc 3D structures revealed that the domain α-L-fucosidase and the GH29 family's catalytic sites were conserved; interestingly, the galactose-binding domain was recognized only in ST1 and ST2. The phylogenetic inferences of ALFuc showed that STs1–3 were clearly identifiable and grouped into specific clusters. Our results show, for the first time through experimental data that ALFuc is a secretion product of Blastocystis sp., which could have a relevant role during intestinal colonization; however, further studies are required to clarify this condition. Furthermore, the alfuc gene is a promising candidate for a phylogenetic marker, as it shows a conserved classification with the SSU-rDNA gene.

Resumen: El presente artículo pretende identificar la influencia del contexto transfronterizo en las aspiraciones educativas de los estudiantes de educación media superior que radican en Tijuana, Baja California. Para este objetivo se estiman modelos de regresión de respuesta cualitativa que consideran variables de índole demográfica y socioeducativa, del ámbito migratorio, y relacionadas con el empeño, la motivación propia y el apoyo familiar. Se utilizan datos recopilados por el Mexican Migration Field Research Program. Se encontró que las expectativas son poco sensibles a las circunstancias migratorias y transfronterizas. En cambio, el nivel educativo de los padres, la dedicación al estudio, tener familiares cercanos estudiando y saber inglés son variables que sí parecen relevantes en la formación de las expectativas. Se concluye que los aspectos demográficos y socioeducativos, así como la dedicación propia y el apoyo familiar, determinan en mayor medida las aspiraciones de los jóvenes.

Abstract: This article aims to shed light on the impact of the cross-border context on educational aspirations of middle and high school students living in Tijuana, Baja California. For this purpose, qualitative response regression models are estimated considering variables of a demographic and socio-educational nature, of the migratory field and related to commitment, self-motivation, and family support. Data was collected by the Mexican Migration Field Research Program is used. We found that expectations are not very sensitive to migratory and cross-border circumstances. On the other hand, the educational level of the parents, dedication to study, have family members at the university and speak English, does seem relevant in the formation of expectations. We concluded that demographic and socio-educational factors, as well as their own effort, and family support determine to a greater extent the aspirations of the youth.

Avaliou-se o crescimento e a produção de enzimas por Aspergillus flavipes FP-500 em pectina, ácido poligalacturônico, ácido galacturônico, arabinose, ramnose, xilose, glicerol e glicose, em diferentes valores de pH inicial. Verificamos que a cepa produziu exopectinases, endopectinases e pectina liases. Exopectinases e pectina liases foram produzidas em níveis basais como enzimas constitutivas e sua produção foi modulada pela fonte de carbono disponível e pelo pH do meio de cultura e estimulada pela presença de indutores no meio de cultura. Endopectinase foi indutível e produzida somente quando pectina foi utilizada como fonte de carbono. Nossos resultados sugerem que as pectinases de A. flavipes FP-500 são produzidas de forma planejada. A primeira enzima a ser produzida foi expopectinase, seguida por pectina liase e endopectinase.

Growth and enzymes production by Aspergillus flavipes FP-500 were evaluated on pectin, polygalacturonic acid, galacturonic acid, arabinose, rhamnose, xylose, glycerol and glucose at different initial pH values. We found that the strain produced exopectinases, endopectinases and pectin lyases. Exopectinases and pectin lyase were found to be produced at basal levels as constitutive enzymes and their production was modulated by the available carbon source and pH of culture medium and stimulated by the presence of inducer in the culture medium. Endo-pectinase was basically inducible and was only produced when pectin was used as carbon source. Our results suggest that pectinases in A. flavipes FP-500 are produced in a concerted way. The first enzyme to be produced was exopectinase followed by Pectin Lyase and Endo-pectinase.

The aim of this work was to describe growth dynamics, substrate depletion and polygalacturonases production by Aspergillus flavipes FP-500 in batch cultures by means of unstructured models. The microorganism was cultivated on several mono- di- and poly- saccharides, and then the culture development modeled with Monod and Leudeking-Piret equations. The kinetic parameters related to the models (µmax, γx/s, α and β) were obtained by minimizing the quadratic residuals function with a simplex algorithm. An accurate description of experimental data was attained with the proposed models. Besides, modeling provided significant kinetic information on microbial degradation of complex substrates, such as the correlation between specific growth rate µmax and production yield α, suggesting that A. flavipes FP-500 polygalacturonases are actually constitutive, but also that there is a certain degree of induciblility in these enzymatic activities.