Export, purification, and activities of affinity tagged Lactobacillus reuteri levansucrase produced by Bacillus megaterium

Fructosyltransferases, like the Lactobacillus reteri levansucrase, are important for the production of new fructosyloligosaccharides. Various His6- and Strep-tagged variants of this enzyme were recombinantly produced and exported into the growth medium using the Gram-positive bacterium Bacillus megaterium. Nutrient-rich growth medium significantly enhanced levansucrase production and export. The B. megaterium signal peptide of the extracellular esterase LipA mediated better levansucrase export compared to the one of the penicillin amidase Pac. The combination of protein export via the LipA signal peptide with the coexpression of the signal peptidase gene sipM further increased the levansucrase secretion. Fused affinity tags allowed the efficient one-step purification of the recombinant proteins from the growth medium. However, fused peptide tags led to slightly decreased secretion of tested fusion proteins. After upscaling 2 to 3 mg affinity tagged levansucrase per liter culture medium was produced and exported. Up to 1 mg of His6-tagged and 0.7 mg of Strep-tagged levansucrase per liter were recovered by affinity chromatography. Finally, the purified levansucrase was shown to synthesize new fructosyloligosaccharides from the novel donor substrates D-Gal-Fru, D-Xyl-Fru, D-Man-Fru, and D-Fuc-Fru.

Skills, Exports, and the Wages of Seven Million Latin American Workers

Los retornos a la educación y el skill premium son parámetros fundamentales en diversos campos y en debates políticos, incluyendo la literatura sobre la globalización y la desigualdad, la migración internacional y el cambio tecnológico. Este artículo explora el skill premium y su correlación con las exportaciones en América Latina, vinculando así el rendimiento de la educación a la literatura emergente sobre la estructura del comercio y el desarrollo. Utilizando los datos sobre empleo y salarios poara más de siete millones de trabajadores de dieciséis economías de América Latina, los autores estiman el rendimiento educativo nacional y el específico de cada industria y el skill premium, y estudian algunos de sus factores determinantes. La evidencia sugiere que tanto los países como las características de las industrias son importantes para explicar los retornos educativos y el skill premium. La evidencia también sugiere que la incidencia de las exportaciones dentro de las industrias, el ingreso promedio per cápita en los países y la abundancia relativa de trabajadores calificados están relacionados con las características subyacentes de las industrias y el país, que explican estos parámetros. En particular, las exportaciones sectoriales se correlacionan positivamente con el rendimiento de la educación a nivel de la industria, un resultado compatible con los últimos modelos comerciales que unían las exportaciones con los salarios y la demanda de trabajo calificado.Centro de Estudios Distributivos, Laborales y Sociales (CEDLAS

Reactive nitrogen and sulphate wet deposition at Zeppelin Station, Ny-Ålesund, Svalbard

As a potent fertilizer, reactive nitrogen plays an important role in Arctic ecosystems. Since the Arctic is a nutrient-limited environment, changes in nitrogen deposition can have severe impacts on local ecosystems. To quantify the amount of nitrogen deposited through snow and rain events, precipitation sampling was performed at Zeppelin Station, Svalbard, from November 2009 until May 2011. The samples were analysed for , nss- and concentrations, and the deposition of single precipitation events was calculated using precipitation measurements taken at nearby Ny-Ålesund. The majority of observed events showed concentrations ranging from 0.01 to 0.1 mg L−1 N for and and from 0.02 to 0.3 mg L−1 S for nss-. The majority of calculated depositions ranged from 0.01 to 0.1 mg m−2 N for and and from 0.02 to 0.3 mg m−2 S for nss-. The budget was controlled by strong deposition events, caused by long-lasting precipitation episodes that lasted for several days and which had raised concentrations of nitrogen and sulphur. Three future scenarios of increasing precipitation in the Arctic were considered. The results showed that deposition is mainly controlled by the amount of precipitation, which leads to the conclusion that increased precipitation might cause increases in deposition of the same magnitude