1000 resultados para Culture evaluativa


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The objective of the present work was to evaluate the capacity of three isolates of Aspergillus flavus to produce aflatoxin under different culture conditions. This experiment was based on a 2³ factorial design, in which the independent variables were temperature (20-40 °C), incubation time (7-21 days), and the pH (2.0-6.0) in two different synthetic media. The optimal conditions were applied to non-aflatoxigenic isolates previously tested in coconut agar. Aflatoxin B1 was extracted directly from the synthetic cultures with chloroform. Thin Layer Chromatography (TLC) and Photographic Photometry were utilized to identify and quantify the compounds. Preliminary results showed that YES agar was an alternative medium for detecting the toxigenic potential of Aspergillus flavus in the following conditions: pH of 5.2, temperature of 25 °C, and incubation time of 11 days producing 206.05 ng.CFU-1 of aflatoxin B1. Of the 30 non-aflatoxigenic isolates, 12 presented a positive result in the optimal media and conditions tested.

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Protease and α-amylase production by a thermophilic Bacillus sp. SMIA-2 cultivated in liquid cultures containing 0.25% (w/v) starch as a carbon source reached a maximum at 18 hours (47 U.mg-1 Protein) and 36 hours (325 U.mg-1 Protein), respectively. Culture medium supplementation with whey protein concentrate (0.1%, w/v) and corn steep liquor (0.3%, w/v) not only improved the production of both enzymes but also enabled them to be produced simultaneously. Under these conditions, α-amylase and protease production reached a maximum in 18 hours with levels of 401 U.mg-1 protein and 78 U.mg-1 protein, respectively. The compatibility of the enzymes produced with commercial laundry detergent was investigated. In the presence of Campeiro® detergent, α-amylase activity increased while protease activity decreased by about 27%. These enzymes improved the cleaning power of Campeiro® detergent since they were able to remove egg yolk and tomato sauce stains when used in this detergent.

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The effect of inulin addition and starters (Kefir grains or commercial starter culture) on the microbial viability, texture, and chemical characteristics of Kefir beverages prepared with whole or skim milk was evaluated during refrigerated storage. The type of starter did not influence microbial viability during the storage of the beverages, but the chemical and textural changes (decreases in pH, lactose concentration, and inulin and increased acidity, firmness, and syneresis) were more pronounced in the formulations fermented with grains than those fermented with the starter culture. The addition of inulin did not influence acidity or viability of lactic acid bacteria, but in general, its effect on the survival of acetic acid bacteria, Lactococcus and yeasts, firmness, and syneresis depended on the type of milk and starter culture used. Generally, the yeast, acetic acid bacteria, and Leuconostoc counts increased or remained unchanged, while the total population of lactic acid bacteria and Lactococcus were either reduced by 1 to 2 logs or remained unchanged during storage.

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In this research, the probiotic Streptococcus thermophilus was inoculated into milk as co-culture to produce probiotic cheese. The effects of using Streptococcus thermophilus with other probiotic bacteria on cheese composition, and microbiological viability during 28 days of storage were investigated. Sensorial properties were determined only at 1st and 28th days of storage. The results showed that the use of Streptococcus thermophilus as co-culture in probiotic cheese production did not affect negatively the cheese components. Fat and dry matter properties of cheese weren't influenced by added probiotic bacteria. However, different level of pH, salt and lactic acid were detected. All probiotic bacteria were present in high levels throughout storage of cheeses, above 7 Log cfu.g- 1, threshold required for probiotic activity. Sensory panel showed that the highest average sensory evaluation points were recorded in cheeses made with Streptococcus thermophilus plus Lactobacillus casei, whereas other probiotic bacteria combinations had been affected less in regard to taste or appearance.

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In biotechnological processes, the culture media components are responsible for high costs and exert a strong influence on the cyanobacteria behavior. The objective of this study was to evaluate the Arthrospira platensis growth potential for biomass production under different cultivation conditions using an experimental design. Three factors that are important for cyanobacteria growth were evaluated: sodium bicarbonate (9 to 18 g/l), sodium nitrate (1.25 to 2.5 g/l), and irradiance (20 to 120 µmol photons/m2.s–1). The results showed that the concentration of NaNO3 in the A. platensis medium can be reduced, resulting in increased concentrations of biomass produced. There was a higher biomass production due to the increase in the concentration of NaHCO3 and irradiance, mainly when these two factors varied tending towards the highest values studied. The results demonstrate the potential to produce Arthrospira platensis with lower costs and effluent generation without affecting cultivation performance.

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Kirjallisuusarvostelu

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In Practices of Inclusion and Exclusion in Premodern Culture a group of Finnish cultural historians discuss the meanings of cultural belonging, experiences and practices of construing boundaries between cultures and their others. What were the motives behind these constructions of differences in Premodern cultures? Why and through what kind of practices were differences created in specific cultural contexts? This book deals with Premodern people having multiple ways of construing their relationship to others, simultaneously being active agents in their own lives. Practices of Inclusion and Exclusion in Premodern Culture is suitable for course book for Master's Degree studies of history.

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Over the years, cross-border mergers and acquisitions have become a popular strategic option for variety of firms. Companies often seek rapid growth through acquiring potentially valuable enterprises or attempting to enhance their organization’s profitability by merging with other firms. However, managing the change of organizational culture is a major managerial challenge as companies often confront difficulties when merging two previously autonomous organizational cultures into one, joint organizational culture. Therefore, the purpose of this study is to increase understanding related to the challenges and possibilities concerning the management of organizational culture change in cross-border mergers and acquisitions. The research question “How to manage the change of organizational culture in cross-border mergers and acquisitions?” is analysed in relation to the theories presented in this thesis regarding organizational culture, organizational change and acculturation as well as in relation with the collected empirical data. The research question is divided into three sub-questions according to the following: (1) “What is the role of organizational culture in organizations?”, (2) “How to manage organizational change in mergers and acquisitions?” and (3) “How to manage organizational culture change through acculturation?”. The thesis is conducted as a qualitative case study research including three personal interviews and one group interview. The interviews were conducted as a combination of semi-structured and unstructured interviews. Theories related to organizational culture, the management of change as well as acculturation are studied and further analysed in relation to empirical material collected by the researcher. Research findings indicate that that several factors can influence the success of managing the organizational culture change in cross-border mergers and acquisitions. Factors such as defining the preferred acculturation model prior the merger; managing the resistance of change; open communication; acknowledgement of local culture and cultural differences; involvement of personnel in change processes; as well as the formulation and implementation of comprehensive change plans proved to be important factors with relation to successful management of organizational culture change

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The purpose of this thesis is to explore Finnish maritime personnel’s conceptions of safety management and its relationship with the concept of safety culture. In addition, the aim is to evaluate the impact of the ISM Code on the prevailing safety culture in the Finnish shipping business. A total of 94 interviewees and seven Finnish shipping companies were involved in this study. Thematic interviews were applied as the main research method for the study. The results were analysed qualitatively. The results indicate that maritime safety culture can simultaneously demonstrate features of integration, differentiation and ambiguity. Basically, maritime personnel have a positive attitude towards safety management systems since they consider safety management beneficial and essential in general. However, the study also found considerable criticism among the interviewees. The interviewed maritime personnel did not criticise the ISM Code as such, yet they criticised the way the ISM Code has been applied in practise. In order to understand the multiple perspectives of safety culture more comprehensively, multiple theoretical perspectives and methodological approaches are needed. This study indicates that safety culture and the impacts of the ISM Code should not be unambiguously studied solely quantitative methods or qualitative methods. By examining safety culture from several methodological and theoretical perspectives, one may gain a more versatile and holistic overview of safety culture.

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Mécénat texte imprimé : Cet ouvrage a été numérisé grâce à Pascale Ladet à l'occasion de l'anniversaire de son Guillaume

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Référence bibliographique : Rol, 58532