The purpose of this work was to model the survival of the microorganism and the kinetics of drying during the encapsulation of Lactobacillus fermentum K73 by Refractance Window drying. A whey culture medium with and without addition of maltodextrin were used as encapsulation matrices. The microorganism with the encapsulation matrices was dried at three water temperatures (333, 343 and 353 K) until reaching balanced moisture. Microorganism survival and thin layer drying kinetics were studied by using mathematical models. Results showed that modified Gompertz model and Midilli model described the survival of the microorganism and the drying kinetics, respectively. The most favorable process conditions found with the mathematical modelling were a drying time of 2460 s, at a temperature of 353 K. At these conditions, a product with 9.1 Log CFU/g and a final humidity of 10% [wet basis] using the culture medium as encapsulation matrix was obtained. The result shows that Refractance Window can be applied to encapsulate the microorganism probiotic with a proper survival of the microorganism.

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SUMMARYThis study aims to evaluate the multifunctional role of whey culture medium during the spray drying microencapsulation of Lactobacillus fermentum K73. Whey culture medium containing growing microorganisms served to hydrate different mixtures (gum arabic, maltodextrin and whey). We evaluated the use of these mixtures as carbon sources and their protective effects on simulated gastrointestinal conditions. The optimal mixture was spray-dried while varying the outlet temperature and atomizing pressure using a response surface design. These conditions served to evaluate microorganism survival, tolerance to gastrointestinal conditions in vitro, physicochemical properties, morphometric features and stability at 4, 25 and 37 °C. Lactobacillus fermentum K73 replicated in the carrier material. Bacterial change cycles were (–1.97±0.16) log CFU/g after the drying process and 
(–0.61±0.08) and (–0.23±0.00) log CFU/g after exposure of the capsules to simulated gastric pH and bile salt content, respectively. The physicochemical properties and morphometric features were within the normal ranges for a powder product. The powder was stable at a storage temperature of 4 °C. The spray drying of the whey culture medium with growing microorganisms using the optimized drying conditions was successful. This study demonstrates the use of whey culture medium as a component of carrier material or as the carrier material itself, as well as its protective effects during drying, under simulated gastrointestinal conditions, and at varied storage temperatures.

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. Optimización de la producción y resistencia al estrés del probiótico Lactobacillus fermentum K73 en un reactor sumergido usando un medio de cultivo a base de suero lácteo RESUMEN 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.

The goal of this study was to determine the effect of the carrier material, drying technology and dissolution media during the passage of L. fermentum K73 through a dynamic in vitro digestion system (IViDiS).