Cloning novel sugar transporters from Scheffersomyces (Pichia) stipitis allowing D-xylose fermentation by recombinant Saccharomyces cerevisiae.

Objectives: Since uptake of xylose limits its fermentation, we aimed to identify novel sugar transporters from Scheffersomyces stipitis that allow xylose uptake and fermentation by engineered Saccharomyces cerevisiae.

Results: An hxt-null S. cerevisiae strain, lacking the major hexose transporters (hxt1Δ-hxt7Δ and gal2Δ) but having high xylose reductase, xylitol dehydrogenase and xylulokinase activities, was transformed with a genomic DNA library from S.

Toward establishing a morphological and ultrastructural characterization of proembryogenic masses and early somatic embryos of Araucaria angustifolia (Bert.) O. Kuntze.

Somatic embryogenesis is a morphogenetic route useful for the study of embryonic development, as well as the large-scale propagation of endangered species, such as the Brazilian pine (Araucaria angustifolia). In the present study, we investigated the morphological and ultrastructural organization of A. angustifolia somatic embryo development by means of optical and electron microscopy.