1,720,962 research outputs found
Expression of Bacillus sp. BP-7 xylanase in Saccharomyces cerevisiae as a fusion with cell wall protein Pir 4
No full textImmobilisation and ethanol stress induce the same molecular response at the level of cell wall in growing yeast
No full textThe effect of immobilization on the cell wall of Saccharomyces cerevisiae cells was investigated in comparison with freely suspended batch grown cells. The pattern of mannoproteins released from the cell wall after Zymolyase digestion showed the presence of new mannoprotein species when cell growth takes place in a state of immobilization. The same result was obtained by exposure of freely suspended cells to a stressful concentration of ethanol, showing that two different adverse culture conditions induce a similar molecular response at the cell wall level
Production in fed-batch Reactor of Bacillus subtilis Lipase A immobilized on its own producer Saccharomyces cerevisiae cells
Full text linkLipases (EC 3.1.1.3, triacylglycerol hydrolases), a subclass of the esterases (EC 3.1.1.1, carboxyl ester hydrolases) are one of the most important groups of biocatalysts for biotechnological uses such as synthesis of biopolymers and biodiesel, production of enantiopure pharmaceuticals, detergent formulation or the production of flavour compounds. Lipases can be commercialized as free or immobilized form.
Nowadays it is of great interest to obtain immobilized enzymes especially for industrial applications since immobilization confers stability giving the possibility to recover the biocatalyst after its use, simplifying downstream processing. In the present work, Lipase A from Bacillus subtilis has been expressed in different strains of the yeast S. cerevisiae as a fusion protein with the yeast cell-wall mannoprotein Pir4.
The corresponding gene fusion was created by inserting all the coding sequence of the lipase A gene in the BglII restriction site of PIR4 gene, leading to the expression of a fusion protein still containing the four cysteine residues responsible for the anchorage of Pir4 to the yeast cell wall.
Production of lipase as a naturally immobilized biocatalyst was carried out allowing yeast cells to proliferate in a fed-batch reactor under glucose limitation to promote a fully respiratory metabolism and consequently high biomass yield. The performance of the producer strains was evaluated in terms of cell density and enzyme productivity. A preliminary study of economic feasibility of a single fermentation run has been performed based on the experimental results obtained
Gelatin immobilized growing yeast cells: changes in the glycosylation level of external invertase and cell wall composition
Full text linkFree and gelatin immobilized yeast cells from two different strains were analyzed by means of SDS-PAGE as regards: i) the glycosylation levels of external invertase before and after treatment with endo-beta-N-acetylglycosaminidase (Endo H), ii) the pattern of mannoproteins released from the cell wall after extraction with SDS, beta-mercaptoethanol and Zymoliase digestion. The results obtain suggest that the composition and structure of the cell wall is modified when cell growth takes place in the state of immobilization
Electrophoretic mobility of external invertase from free and gel-immobilized yeast cells
No full textElectrophoretic mobility of secreted invertase (E.C.3.2.1.26) from gelatin immobilized yeast cells was analyzed and prepared with that of secreted invertase from freely suspended batch grown cells. Invertase from immobilized cells showed a lower mobility after 24 h opf incubation, in medium containing either glucose or raffinose as carbon source. Changes in invertase mobility were also followed in a time course both for immobilized and for freely suspended batch grown cells. Mobility of invertase from free cells increased an approximately 15 h of incubation, independently of the carbon source, whilst that of invertase from immobilized cells remained constant. The differences observed were attributed to a different level of glycosylation of the protein moiety in free and immobilized cells. The amount of mannnoproteins in the cell walls of immobilized cells was also investigated by ConA ferritin labelling and quantification of ferritin particle density in ultrathin sections; the results of this experiments showed a higher content of mannoproteins in the walls of immobilized cells when compared with free cells. As a whole, these results are indicative of physiological changes can be ascribed to the peculiar microenvironment of gel-immobilized cell
Expression of human interleukin-1β in Saccharomyces cerevisiae using PIR4 as fusion partner and production in aerated fed-batch reactor.
Full text linkTo circumvent cell wall retention commonly associated to Saccharomyces cerevisiae when used as a host for heterologous protein production, we have created a translational fusion of human interleukin-1β (IL-1β) to the
Pir4 cell wall protein, so as to drive the secretion of the recombinant product to the growth medium. The auxotrophic S. cerevisiae BY4741 was used as host to express the Pir4-IL1β fusion protein. Once it was ascertained that the fusion protein was secreted to the culture medium andbehaved as a growth-linked product, S. cerevisiae BY4741 [PIR4-IL1β] was cultured in an aerated fed-batch reactor to achieve high cell density and, consequently, high product concentration in the medium. Two cultivation media were employed, a rich complex and a defined mineral medium, the latter suitably supplemented with bacto-casamino acids as ACA (auxotrophy-complementing amino acid) source. The rich complex medium allowed a good performance of the producer strain only during batch growth, but was revealed to be inadequate for long-term fed-batch operations. The defined mineral medium ensured a better performance, even though not yet satisfactory in spite of a proper ACA supplementation. The behaviour of BY4741 was attributed to an intrinsic sensitivity of the producerstrain to long-term aerated fed-batch operations
Use of the cell wall protein Pir4 as a fusion partner for the expression of heterologous proteins in Saccharomyces cerevisiae
No full textABSTRACT and POSTER.
IX FISV Annual Congress.
RIVA DEL GARDA (TN), September 26-29 200
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
- …
