Assessment of Different Lactic Acid Bacteria Isolated from Agro-Industrial Residues: First Report of the Potential Role of Weissella soli for Lactic Acid Production from Milk Whey

Abstract: The production of lactic acid (LA) through the microbial conversion of agro-industrial residuals is an important process in the biotechnology industry. The growth kinetics of 30 strains of lactic acid bacteria (LAB) isolated from agro-industrial residues were determined and nine strains were selected for microbioreactor fermentation. Lactiplantibacillus pentosus_70-1 (1.662) and L. pentosus_ 19-2 (1.563) showed the highest OD600 values, whereas the highest growth rates were observed for L. pentosus_19-2 (0.267 h−1) and Weissella soli_31 (0.256 h−1). The production of LA and acetic acid (AA), glucose consumption, and metabolic profiles were determined, without finding significant differences in the production of LA; however, W. soli_29 produced the highest amount of LA (20.833 gL−1) and was able to metabolize most of the studied carbohydrates. Based on these results, W. soli_29 was chosen for a 20 h fermentation in a 7 L bioreactor using both standard medium and milk whey supplemented medium. W. soli_29 produced 16.27 gL−1 and 7.21 gL−1 of LA in each of these mediums, respectively. These results show the underlying potential of Weissella strains for biotechnological applications. Additional analysis which should contemplate different agro-industrial residues and other conditions in bioreactors must be carried out.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Centro de Investigación en Enfermedades Tropicales (CIET)UCR::Vicerrectoría de Docencia::Salud::Facultad de MicrobiologíaUCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería de BiosistemasUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro Nacional de Ciencia y Tecnología de Alimentos (CITA

Determinación de humedad en la pulpa de café

Texto sin OCREl propósito de este trabajo fue adaptar el método del honor de convención forzada para la determinación del contenido de humendad de la pulpa de café. Se realizó una prueba preliminar para establecer el tiempo necesario para estabilizar el peso de una muestra de alta humedad, utilizando una temperatura de 103°C y muestras de 5,00 g; el tiempo establecido fue de 2 h. Se estudiaron 3 lotes de pulpa de café cada uno con un contenido de humedad diferente (bajo, intermedio y alto). De cada lote se pesaron 36 muestras de 5,00 g, se colocaron en el horno a 103°C y cada 10 min por 2 h se sacaron 3 muestras al azar para determinar el porcentaje de humedad. Las muestras se analizaron por duplicado en diferentes ocasiones, y simultáneamente por le método de Bidwell-Sterling (destilación con tolueno) utilizado como método de referencia. Se desarrollaron curvas del % de humedad con los resultados obtenidos utilizando el método del horno. y además se estableció la correlación entre los resultados de ambos métodos. Las humedades en base húmeda (bh) de los 3 lotes se establecieron en 17,6%, 33,6% y 64,6% respectivamente por el método del horno, y en 17,5%, 34,2% y 64,5% por el método de Bidwell-Sterling. Ambos resultados se correlacionaron y mostraron una correspondencia lineal que se ajustó con un coeficiente de determinación alto (R2=0,9991). Las curvas % de humedad mostraron que la broza de humedad baja se estabiliza en menos tiempo pero en todos los casos el tiempo mínimo fue de 1,5 h. Un análisis de los datos demostró que utilizar 3 repeticiones por muestra garantiza una desviación estándar <0,5% entre ellos. Se concluye que los porcentajes de humedad de pulpa de café obtenidos con la adaptación propuesta tienen una alta correlación con los obtenidos por el método Bidwell-Sterling y presenta ventajas, respecto a este, en cuanto a la cantidad de repeticiones y la simultaneidad del análisis, además de ser menos laborioso, no requerir personal especializado, ser más barato y representar menor contaminación ambiental.The aim of this study was to adapt the forced convection oven method to determine % humidity of coffe pulp. A preliminary study was done to establish time necessary to stabilize the weight of 5,00g samples of a high humidity coffee pulp using 103°C in the oven. Time was established in 2 h. Three coffee pulp lots with different humidites (low, intermediate, high) were studied. From each lot 36 5,00g samples were introduced in a pre-heated oven at 103°C, and every 10 min up to 2 h 3 samples were taken at random to determine humidity percent. Samples were analysed in duplicate, and simultaneously by the Bidwell-Sterling method used as reference. With data obtained humidity % curves were plotted, and correlation between results by both methods was studied. Humidity %, on wet basis, for the 3 coffee pulp lots were 17,6%, 33,6%, 64,6% for the oven method, and 17,5%, 34,2%, 64,55% for the Bidwell-Sterling method. Results correlated and showed a linear correpondence which adjusted to a high determination coefficient (R2=0,9991). Humidity percent curves shiwed that low humidity coffee pulp stabilizes in less time, but in all three cases minimum time was 1,5 h. When % standard deviation of data obtained at each 10 min interval was studied, it was found that using 3 repetions per sample guarantees <0,05% standard deviation between the 3 samples after 1 h. The method proposed has a strong correlation to the Bidwell-Sterling method and presents advantages to it in the amount of repetitions that can be done simultaneously, it is less laborious, it doesn´t require specialized personnel, it is cheaper, and represents less environmental contamination.UCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería de BiosistemasUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Modelling the Effect of Salt Concentration on the Fate of <i>Listeria monocytogenes</i> Isolated from Costa Rican Fresh Cheeses

“Turrialba cheese” is a Costa Rican fresh cheese highly appreciated due to its sensory characteristics and artisanal production. As a ready-to-eat dairy product, its formulation could support Listeria monocytogenes growth. L. monocytogenes was isolated from 14.06% of the samples and the pathogen was able to grow under all tested conditions. Due to the increasing demand for low-salt products, the objective of this study was to determine the effect of salt concentration on the growth of pathogen isolates obtained from local cheese. Products from retail outlets in Costa Rica were analyzed for L. monocytogenes. These isolates were used to determine growth at 4 °C for different salt concentration (0.5–5.2%). Kinetic curves were built and primary and secondary models developed. Finally, a validation study was performed using literature data. The R2 and Standard Error of fit of primary models were ranked from 0.964–0.993, and 0.197–0.443, respectively. An inverse relationship was observed between growth rate and salt concentration. A secondary model was obtained, with R2 = 0.962. The model was validated, and all values were Bf > 1, thus providing fail-safe estimations. These data were added to the free and easy-to-use predictive microbiology software “microHibro” which is used by food producers and regulators to assist in decision-making