1,720,966 research outputs found
DEVELOPMENT OF A LOW COST CULTURE MEDIUM FOR SAKACIN A PRODUCTION BY L. SAKEI
No full textMRS is currently the medium of choice for promoting sakacin A production by L. sakei (180 AU/ml): however, this medium is expensive and not applicable for large scale production. In the present study, an OVAT (One Factor at a Time) approach was used to formulate an alternative culture medium.
The subsequent full factorial design (25) investigated the influence of ingredients on bacteriocin production and interactions among the ingredients. A series of adaptation steps were used to develop an equation model that allowed for estimation of all first order variables and sakacin production. The formula of the alternative culture medium consisted as follows (g/l): bacto peptone (X1) 10, meat peptone (X2) 8, yeast autolysate (X4) 4, glucose 10, CaCO3 30, inoculum 5 % (v/v) and use of deionised water. The cost of the alternative medium was approximately half that of MRS and sakacin A production was increased from 180 to 480 AU/ml
Attività anti-Listeria della sakacina A, batteriocina potenzialmente impiegabile nel settore dell'active packaging
No full textInfluence of substrate on beta-galactosidase production by Kluyveromyces strains
Full text linkThe aim of the present research was to investigate the influence of culture conditions on the levels of β-galactosidase (EC 3.2.1.23) activity produced by Kluyveromyces strains. Interest was focused on evaluating enzyme activity levels when lactose or cheese whey was employed as substrate in culture medium formulation. From an overall look at the obtained results, the tested strains were found to be able to produce β-galactosidase at promising levels. The use of cheese whey, either for strain maintenance and production trials, allowed to obtain a high cell yield associated with β-galactosidase production. The maximum β-galactosidase volumetric activity, EA max 66.5 IU/ml, corresponding to 3184 EAspec IU/g cell dw, was obtained with K. marxianus MIM 782 at 37 °C and 72 h incubation
Influence of temperature and sakacin A concentration on survival of Listeria innocua cultures
No full textThe antimicrobial activity of sakacin A, a bacteriocin produced by L. sakei, was investigated at 30, 10 and 4 °C against L. innocua in stationary and lag phases of growth. When sakacin was added to L. innocua cells in stationary phase, two death kinetics were observed. Populations of L. innocua were reduced up to three log cycles when sakacin A was increased from 0 (control) to 1600 AU ml-1. When sakacin A was added to L. innocua cells in lag phase, lag time, inhibition time and rate were proportionally extended, and maximum population decreased when employing higher bacteriocin levels. Sakacin A was found to influence L. innocua growth, a microorganism able to grow at 4 °C. At refrigerated temperatures, the addition of sakacin A was found to inhibit L. innocua cell growth. Sakacin A may be considered a promising molecule to be used as antimicrobial agent to preserve the shelf life of refrigerated foods
Purified sakacin A shows a dual mechanism of action against Listeria spp: proton motive force dissipation and cell wall breakdown
Full text linkSakacin A was purified to homogeneity through simple chromatographic procedures from cultures of Lactobacillus sakei DSMZ 6333 grown on a low-cost medium. The highly purified protein dissipated both transmembrane potential (ΔΨ) and transmembrane pH gradient (ΔpH) in Listeria cells in a very intense, rapid, and energy-dependent fashion. On a slower timescale, purified sakacin A also showed a lytic activity toward isolated cell walls of Listeria. Mass spectrometry was used to analyze the products of sakacin A action on cell walls, evidencing that sakacin A acts on various types of bonds within peptoglycans
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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