CERELA   05438
CENTRO DE REFERENCIA PARA LACTOBACILOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The effect of ph and growth phase on the heat tolerance of the inmunobiotic Lactobacillus rhamnosus CRL 1505.
Autor/es:
S. SALVA; G. FONT ; G.I. MARTOS; M.A. CORREA DEZA; C.L. GEREZ
Lugar:
San Miguel deTucumán
Reunión:
Congreso; V Simposio Internacional de Bacterias Lácticas.; 2016
Institución organizadora:
CERELA
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 fermenteddairy products; it is also produced as dehydrated powder (spray dried)for subsequent addition into different raw matter to improve transportation and storage. Spray drying is used because ofits 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 culture pH and the physiological age of L. rhamnosusCRL 1505 on the cell heat toleranceto improve the survivalrate to the process. Fermentations were performed at 37°C in MCM 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 citometry using the BD? Cell Viability Kit to provide insights into the 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. rhamnosuswas significantly different under controlled pHconditions.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, adecrease in live cells together with an increase in injured and dead cells was observed at the stationary phase infree and in pH 6.0-controlledcultures.Particularly, the percentage of live cells did not decreaseat stationary phaseunderpH 5.5. Results of both flowcytometry and plate count showed that the exponential phase cells were more(2.7-9 times) heat tolerant than stationary phase cellsunder controlled pH conditions. Best results (100% survival post-heat shock) were obtained for exponential phase cells of free-pH cultures. The amount of injured cells post heat shock, however, was > 30 %which were partially recovered in agarized medium.This study evinces that controlled pH conditionsfor growingL. rhamnosusCRL 1505 resulted in less tolerance to heat stress, condition which is frequently used for starter culture manufacture. Further studies are necessary to optimize the bioprocess from the basis of these observations.