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7 páginas The aim of this study was to develop a culture medium based on whey for the improvement of the probiotic characteristics of Lactobacillus fermentum K73 in submerged culture. Response surface methodology was used to determine the effects of culture conditions (whey and yeast extract concentration, pH, and agitation) on growth and probiotic characteristics of the lactic acid bacterium. Results showed that whey and yeast extract concentrations were the most influential variables in the responses. The conditions for maximal final cell count (10.783 log (CFU/ml)), minimal lag phase duration (1.022 h), minimal decrease under acid stress conditions (0.097 log (CFU/ml)) and a decrease in biomass in the presence of 0.3% bile salts of 2.58 log (CFU/ml) were: 44.6 g/L of whey, 25 g/L of yeast extract, pH 5.5 and an agitation rate of 100 rpm. These results are the first to indicate that the optimization of the expression of probiotic characteristics of microorganisms is feasible. El objetivo de este estudio fue el desarrollo de un medio de cultivo basado en suero para mejorar las características probióticas de Lactobacillus fermentum K73 en cultivo sumergido. Se usó la metodología de superficie de respuesta (RSM) para determinar los efectos de las condiciones de cultivo (concentración de suero y extracto de levadura, pH y agitación) sobre el crecimiento y características probióticas de la bacteria láctica. Los resultados mostraron que las concentraciones de suero y extracto de levadura fueron las variables de mayor importancia. Las condiciones para una máxima cuenta celular final (10.783 log (UFC/ml)), una mínima duración de la fase lag (1.022 h), una mínima disminución en concentración bajo condiciones de estrés ácido (0.097 log (UFC/ml)) and en presencia de 0.3% de sales biliares (2.58 log (UFC/ml)) fueron: 44.6 g/L de suero, 25 g/L de extracto de levadura, pH 5.5 and y una velocidad de agitación de 100 rpm. Estos resultados son los primeros en indicar que es posible optimizar la expresión de características probióticas de microorganismos.

18 páginas The aim was to study the effect of sublimation temperature (from –20 C to –10 C) and sublimation time (from 18 to 40 h) on the viability of Lactobacillus fermentum K73, the moisture content and the texture features by response surface methodology. The stability of the freeze-dried powders was studied; these powders were stored at 4 C, 25 C, and 37 C for 36 days. Four different matrices were used: culture medium (8% total solids), the mixture of this solution with maltodextrin: whey (0.6: 0.4), with maltodextrin or whey (40% total solids). Results showed that the sublimation conditions to increase cell viability (>8.755 log CFU/g) and to decrease moisture content (

Gelling agents are components to solidify media cultures facilitating the isolation of microorganisms in pure cultures. Agar is the most used gelling agent in microbiological field because of properties like gelling temperature and a desirable texture (high firmness and low adhesiveness). A current problem with agar manufacture is that overexploitation of the algae Gelidium spp is affecting the species conservation and has increased agar’s market price by up to 300%. The aim of this research was to propose substitutes of bacteriological agar in terms of texture by using some reported gelling agents used by food and agroindustry. To determine the effects of the components on texture, were proposed a mixture-design screening to establish an optimal mixture that replace agar. The optimal result, according to the desirability function, were composed of arabic gum (2%), gelan gum (0.5%) and carrageenan (0.5%). This mixture exceeds the firmness of the reference matrix (agar at 2%) by 15% and is potentially 25% more cheaper and without significative statistical difference in growth CFU when compared to agar based media. Resumen Los agentes gelificantes son componentes que solidifican medios de cultivo para facilitar el aislamiento de microorganismos en cultivos puros. El agar es el agente gelificante más utilizado en el campo microbiológico debido a propiedades como su temperatura de gelificación y una textura deseable (alta firmeza y baja adhesividad). El problema actual de la producción de agar es que la sobreexplotación de las algas Gelidium spp está afectando la conservación de la especie y ha aumentado su precio de mercado hasta en un 300%. El objetivo de esta investigación fue proponer sustitutos del agar bacteriológico en términos de textura mediante el uso de algunos agentes gelificantes utilizados por la industria de alimentos y la agroindustria. Para determinar los efectos de los componentes en la textura, se propuso un diseño de mezcla tipo screening para establecer una mezcla óptima que reemplace el agar. El resultado óptimo, según la función de deseabilidad, se compone de goma arábiga (2%), goma gelan (0,5%) y carragenina (0,5%). Esta mezcla superó la firmeza de la matriz de referencia (agar al 2%) 15% y es potencialmente un 25% más económica. Además, no presentó una diferencia estadísticamente significativa en el conteo de UFC en comparación con los medios basados en agar.

Probiotic products are viewed as an alternative to the use of antibiotics in freshwater fishes farming. Probiotic organisms include bacteria, yeast, and filamentous fungi offering different benefits to fish including growth promotion, inhibition of pathogen colonisation, and improvement of nutrient digestion, water quality, and stress tolerance, as well as enhancement of reproduction. For these reasons, this review aims to identify the main trends in probiotic amendment in freshwater fishes. Strategies to incorporate the probiotic strains in the fish feed or pellets to allow optimal viability of the strains as they reach the fish gastrointestinal tract (GIT) are crucial in probiotic research and commercial applications for freshwater fish.