How Parents Perceive the Potential Risk of a Child-Dog Interaction.

Dog attacks on children are a widespread problem, which can occur when parents fail to realise a potentially dangerous interaction between a dog and a child. The aim of the study was to evaluate the ability of parents to identify dangerous situations from several everyday child-dog interactions and to determine whether the participants connected these situations to a particular breed of dog. Five sets of photographs depicting potentially dangerous interactions from everyday situations between children and three dogs (one of each breed) were presented via an online survey to parents of children no more than 6 years old. Data from 207 respondents were analysed using proc GLIMMIX in SAS program, version 9.3. The probability of risk assessment varied according to dog breed (p < 0.001) as well as to the depicted situation (p < 0.001). Results indicated that Labrador Retriever was considered the least likely of the three dogs to be involved in a dangerous dog-child interaction (with 49% predicting a dangerous interaction), followed by Parson Russell Terrier (63.2%) and American Pit Bull Terrier (65%). Participants considered one particular dog-child interaction named 'touching a bowl' a dangerous interaction at a high rate (77.9%) when compared with the other presented situations, which were assessed as dangerous at rates of 48.4% to 56.5%. The breed of dog seems to be an influential factor when assessing a potentially dangerous outcome from a dog-child interaction. Contrary to our hypothesis, interactions involving the small dog (Russell Terrier) were rated more critically, similarly to those of the Pit Bull Terrier. These results suggest that even popular family dog breeds, such as Labrador Retrievers, should be treated with more caution.

Towards the design of an optimal strategy for the production of ergosterol from Saccharomyces cerevisiae yeasts.

The total yield of ergosterol produced by the fermentation of the yeast Saccharomyces cerevisiae depends on the final amount of yeast biomass and the ergosterol content in the cells. At the same time ergosterol purity-defined as percentage of ergosterol in the total sterols in the yeast-is equally important for efficient downstream processing. This study investigated the development of both the ergosterol content and ergosterol purity in different physiological (metabolic) states of the microorganism S. cerevisiae with the aim of reaching maximal ergosterol productivity. To expose the yeast culture to different physiological states during fermentation an on-line inference of the current physiological state of the culture was used. The results achieved made it possible to design a new production strategy, which consists of two preferable metabolic states, oxidative-fermentative growth on glucose followed by oxidative growth on glucose and ethanol simultaneously. Experimental application of this strategy achieved a value of the total efficiency of ergosterol production (defined as product of ergosterol yield coefficient and volumetric productivity), 103.84 × 10-6 g L-1 h-1 , more than three times higher than with standard baker's yeast fed-batch cultivations, which attained in average 32.14 × 10-6 g L-1 h-1 . At the same time the final content of ergosterol in dry biomass was 2.43%, with a purity 86%. These results make the product obtained by the proposed control strategy suitable for effective down-stream processing. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:838-848, 2017.

Optimization of feeding strategy for the ergosterol production by yeasts saccharomyces cerevisiae / Optimización de la estrategia de alimentación para la producción de ergosterol por levaduras saccharomyces cerevisiae

Objective of this study was to optimize ergosterol production by yeast strain Saccharomyces cerevisiae with the use of computer controlled feeding of cultivation medium. Baker´s yeasts strain of Saccharomyces cerevisiae originally modified and selected as mutant D7 was further applied in an industrial scale and also in this investigation. Composition of cultivation medium was optimized with the use of a modified Rosenbrock´s method with regard to following components: glucose, yeast extract, ammonium sulphate, potassium dihydrogen phosphate, magnesium sulphate and calcium chloride. Cultivation of yeast culture was performed in 7 L laboratory bioreactor with a working volume of 5 L equipped with a control unit and linked to a computer, with dissolved oxygen tension measurement, oxygen and carbon dioxide analyzers. BIOGENES prototype software was created from the commercial control system Genesis for Windows 3.0 (GFW), from Iconics and CLIPS 6.04 for the PC-Windows platform. From various factors affecting sterol biosynthesis a specific growth rate was chosen. Feed rate was controlled according to mathematical model. In this case it dealt with a design of optimal profile of specific growth rate with consequent calculation of carbon dioxide profile. Sterol concentration in the dry biomass increased from 1.0 % up to 3 %.

El objetivo de este estudio fue optimizar la producción de ergosterol por una cepa de levadura Saccharomyces cerevisiae, controlando la alimentación de medio de cultivo por computadora. La cepa de levadura panadera Saccharomyces cerevisiae originalmente modificada y seleccionada como mutante D7 fue posteriormente utilizada a escala industrial y también para esta investigación. La composición del medio de cultivo fue optimizada usando el método modificado de Rosenbrock respecto a los siguientes componentes: glucosa, extracto de levadura, sulfato de amonio, fosfato dihidrógeno de potasio, sulfato de magnesio y cloruro de calcio. El cultivo de las células de levadura se llevó a cabo en un biorreactor de laboratorio de 7L con un volumen de trabajo de 5L, equipado con una unidad de control conectada a una computadora, con medición de la tensión de oxígeno disuelto y analizadores de oxígeno y dióxido de carbono. Un software prototipo BIOGENES fue creado a partir del sistema de control comercial Genesis para Windows 3.0 (GFW), de Iconics y CLIPS 6.04 para la plataforma de PC-Windows. A partir de varios factores que afectan la biosíntesis de esterol se escogió una tasa específica de crecimiento. La tasa de alimentación se controló mediante un modelo matemático. En este caso, se trató con un diseño de perfil óptimo de tasa de crecimiento específico con un consecuente cálculo del perfil de dióxido de carbono. La concentración de esterol en la biomasa seca se incrementó desde 1,0% hasta 3%.