CERELA   05438
CENTRO DE REFERENCIA PARA LACTOBACILOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
THE EFFECT OF GROWTH PH AND GROWTH PHASE ON HEAT TOLERANCE OF IMMUNOBIOTIC LACTOBACILLUS RHAMNOSUS CRL 1505
Autor/es:
CORREA DEZA, MA; GEREZ, CL; MARTOS, GI; SALVA, SUSANA; FONT, G
Lugar:
San Miguel de Tucumán
Reunión:
Simposio; V Simposio Internacional de Bacterias Lácticas (SIBAL); 2016
Institución organizadora:
Centro de Referencia para Lactobacilos (CERELA-CONICET)
Resumen:
Oral administration of the immunobiotic Lactobacillus (L.) rhamnosus CRL 1505 stimulates the immune response in gut and respiratory mucosal. Currently, concentrated culture is used for fermented dairy products; it is also produced dehydrated powder (spray drying) for subsequent addition into different raw matter to improve transportation and storage. Spray drying is used because of its lower cost compared to freeze-drying. The success of cell survival depends on the strain since this technique involves heat stress that causes loss of cell viability. The aim of this work was to evaluate the effect of growth pH and the physiological age of L. rhamnosus CRL 1505 on the cell heat tolerance. Fermentations were performed at 37°C in CERELA medium under free and controlled pH (5.5 and 6.0). Cells in mid-exponential phase and stationary phase of growth were harvested and subjected to heat shock (60°C, 5 min). The viability before and after heat shock was evaluated by plate count and flow cytometry using the BD? Cell Viability Kit to provide insights into probiotic survival based on the integrity of the cell membrane by differentiating three kind of populations: live, dead and injured cells. The growth of L. rhamnosus was significantly different under controlled pH conditions. The lag phase was 4 h at free pH and 8 h under controlled pH without differences in specific growth rates (0.31-0.36 h-1). During growth, a decrease in live cells together with an increase in injured and dead cell was observed at the stationary phase in free and in pH 6.0-controlled cultures. Particularly, the percentage of live cells did not decrease at stationary phase under pH 5.5. After heat shock, the cells in exponential phase were more (2.7-9 times heat tolerance than the microorganism growing in stationary phase under controlled pH conditions. Best results (100% survival post-heat shock) were obtained for expotencial phase cells of free-pH cultures. However, flow cytometry results showed > 30% post heat shock injured cells, which were partially recovered in agarized medium. This study evidences that controlled pH conditions for growing L. rhamnosus CRL1505 resulted in less tolerance to heat stress, condition which is frequently used for starter culture manufacture. Further studies are necessary to optimize the spray drying bioprocess from the basis of these observations.