Effect of residual moisture content on the survival of freeze-dried bacteria during storage under various conditions

Real time stability and viability prediction of the anticancer BCG after lyophilization

To test if trehalose could be a better cryoprotectant for BCG than the usually used lactose and predict viability of BCG during shelf-life, BCG was suspended into three stabilizer systems containing 15% w/v trehalose, trehalose-gelatin mixture (in ratio, 30:1 w/w) or lactose. Each formula was lyophilized and several quality parameters were tested before and after lyophilization including sterility, safety, viability, morphology and moisture content. Samples of lyophilized formulae were tested for their reconstitution time and others were charged to stability chambers at 5°C for the performance of real time study. Shelf-life of each formula was estimated and correlation between moisture content and loss in viability was established at each time interval of the real time stability study. Sterility, safety and morphology were retained after lyophilization. Just after lyophilization, minute diminish in viability was observed in the presence of each stabilizer (0.02-0.05%). There was no significant difference in reconstitution time of the three lyophilized formulae. Lactose BCG had the highest shelf-life among the used cryoprotectants during the real time stability studies. Also, moisture content was highly correlated to viability with correlation coefficient ranged between 0.97 and 0.99 and so, the former could be used for prediction of viability throughout the vaccine shelf-life.

Effect of Drying Medium on Residual Moisture Content and Viability of Freeze-Dried Lactic Acid Bacteria

The effect of various substances on the relationship between residual moisture content and the viability of freeze-dried lactic acid bacteria has been studied. Compounds such as polymers, which display considerable ability in displacing water, showed no protective action during freeze-drying. Adonitol, on the other hand, produced the smallest change in water content at various times during drying and allowed the highest rate of survival.