RESUMEN
The present investigation represents the effect of freeze drying on some properties as acid and bile tolerance of Streptococcus thermophilus MTCC 1938 culture isolated from dairy products. The cell paste obtained from milk based medium was freeze dried with a pressure of 50-100 mtorr for 24h at -40ºC. Acid and bile tolerance test exhibited 3.8-4.9 and 3.2-3.8 log counts reduction after freeze drying respectively.
Asunto(s)
Ácido Láctico/análisis , Crioprotectores/análisis , Levadura Seca/análisis , Productos Lácteos/análisis , Leche , Streptococcus thermophilus/aislamiento & purificación , Microbiología de Alimentos , Muestras de Alimentos , Liofilización , Métodos , MétodosRESUMEN
The main factors which affect the cryopreservation of munne splenic lymphocytes were studied. The results showed that DMSO had some toxic effects on lymphocytes when their concentration was more than 10%. However, when their concentration was 10%, they could effectively protect the cells from freezing injuries and had not significant toxicity. The cooling rate giving optimal survival was 1℃/min. Compared with the lymphocytes sealed in HF bags, the functional recovery of fast frozen (6℃/min)lymphocytes sealed in plastic tubes decreased more severely. Diluting the thawed lymphocytes slowly or at 25-30℃gave more greatly improved recovery than rapidly or at ice bath. Lysing RBC by Tris-NH4C1 might increase the susceptibility of splenic lymphocytes from some strain mice to cryoinjuries. Using selected optimal conditions, the viability tested by Trypan Blue Dye Exclusion and the functions measured by [3H] -TdR incorporation of splenic lymphocytes in response to Con A, LPS and MLR in vitro or the ability to initiate GVHD in vivo were well cryopreserved. The time of storage at-196℃ did not affect the function of lymphocytes in this report.