1,720,966 research outputs found
Factors affecting glycerol production by a bioconversion process with a triose phosphate isomerase deficient mutant of Saccharomyces cerevisiae
No full textThe economics of bioglycerol production depend on several factors such as selection of suitable microorganism, exploitation of inexpensive raw materials and optimization of the process. In this work we studied the influence of some parameters on the bioconversion process for the production of glycerol from glucose using a S. cerevisiae strain lacking triose phosphate isomerase activity. The results indicate that the mode of addition of carbon source affects glycerol yield. The bioconversion process can be carried out in a medium containing only glucose and phosphate; a glucose concentration over 20 g/L must be maintained in order to obtain high yield and productivity. The best growth condition to obtain efficient biomass for the bioconversion process is on rich media containing 1.5% ethanol and 0.1% glucose. It is important to collect the biomass at the end of the exponential phase of growth and after an induction in the presence of 0.1% glucose
Glycerol production in a triose phosphate isomerase deficient mutant of Saccharomyces cerevisiae
No full textInteresting challenges from metabolically engineered Saccharomyces cerevisiae cells arise from the opportunity to obtain yeast strains useful for the production of chemicals. In this paper, we show that engineered yeast cells deficient in the triose phosphate isomerase activity are able to produce glycerol without the use of steering agents. High yields of conversion of glucose into glycerol (80-90% of the theoretical yield) and productivity (1.5 g L(-1) h(-1)) have been obtained by a bioconversion process carried out in a poor and clean medium. We obtained indications that the growth phase at which the biomass was collected affect the process. The best results were obtained using cells collected at the end of exponential phase of growth. In perspective, the strategies and the information about the physiology of the cells described here could be useful for the developing of new biotechnological processes for glycerol production, outflanking the problems related to the use of high level of steering agents
Selection of yeast cells with a higher plasmid copy number in a Saccharomyces cerevisiae autoselection system
No full textAutoselection systems allow the selection of a genetically engineered population independently of the growth medium composition. The structure of a Saccharomyces cerevisiae population transformed with an autoselection plasmid, in which a carbon-source-dependent modulation of the plasmid copy number occurs, was analysed. By means of flow cytometric procedures we tested the cell viability, dynamics of growth and heterologous protein production at single cell level. Such analyses allow the identification and the tracking of a specific cellular sub-population with a higher plasmid copy number which arises after the carbon source shift. The effects of the cellular plasmid distribution on the dynamics of growth are also discussed
FERMENTATION OF WHEY AND STARCH BY TRANSFORMED SACCHAROMYCES-CEREVISIAE CELLS
No full textAmong the main agro-industrial wastes, whey and starch are of prime importance. In previous work we showed that strains of Saccharomyces cerevisiae transformed with the episomal plasmid pM1 allow production of yeast biomass and ethanol from whey/lactose. Ethanol production from whey and derivatives has been improved in computer-controlled bioreactors, while fermentation studies showed that the composition of the medium greatly modulates the productivity (g ethanol produced/l in 1 h of fermentation). A yeast strain for the simultaneous utilization of lactose and starch has also been developed. Biotechnological perspectives are discussed
PRODUCTION OF FRUCTOSE DIPHOSPHATE BY BIOCONVERSION OF MOLASSES WITH SACCHAROMYCES-CEREVISIAE CELLS
No full textSugar beet molasses was used as carbon source for Saccharomyces cerevisiae growth and as substrate for bioconversion to fructose diphosphate. The highest level of fructose diphosphate (26.6 g/L) was reached after 10 h incubation of permeabilized cells under appropiate molasses and phosphate to cell ratio and represented a 64% yield of bioconversion
Isolation, nucleotide sequence, and physiological relevance of the gene encoding triose phosphate isomerase from Kluyveromyces lactis
No full textLack of triose phosphate isomerase activity (TIM) is of special interest because this enzyme works at an important branch point of glycolytic flux. In this paper, we report the cloning and sequencing of the Kluyveromyces lactis gene encoding TIM. Unlike Saccharomyces cerevisiae Delta TPI1 mutants, the K. lactis mutant strain was found to be able to grow on glucose. Preliminary bioconversion experiments indicated that, like the S. cerevisiae TIM-deficient strain, the K. lactis TIM-deficient strain is able to produce glycerol with high yield
COPY NUMBER MODULATION IN AN AUTOSELECTION SYSTEM FOR STABLE PLASMID MAINTENANCE IN SACCHAROMYCES-CEREVISIAE
No full textEfficient expression of a foreign gene requires a stable vector present at a high number of copies per cell. We have constructed an autoselection system for the stable maintenance of expression vector in the yeast Saccharomyces cerevisiae that uses the fructose 1,6-bisphosphate aldolase gene (FBA1) to stabilize plasmids in cells bearing a disruption of the chromosomal FBA1 gene. This system allowed us to obtain stable production of a reporter heterologous enzyme (Escherichia coli beta-galactosidase) in rich media. By using an inducible promoter to regulate the expression of FBA1 gene, we have also obtained the modulation of plasmid copy number by carbon source
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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