Comparative Microbial Viability

The goal was to prepare and compare the effect of storage on the viability of probiotics of two different delivery formats – as a Gelcap capsule or admixed with a food/diet. Frozen food was prepared by mixing AIN-93M Purified Rodent Diet (Dyets Inc.) with freeze dried probiotic bacteria (S. thermophilus 11.6×10^9, L. acidophilus 1×10^9, B. longum 1×10^9 cfu/dose) mixed with 10% sterile honey. Capsules were prepared by mixing same composition of probiotic by manual capsule filler. Frozen food was stored at -20deg while capsule was stored at 4 deg. The selective enumeration of microbe were carried out on ST agar for S. themophilus count, MRS salicin for Lactobacillus acidophilus, and MRS cystein agar for B. longum by standard plate count method.

The survival of samples before storing in freezer or refrigerator was used as the control against 8 weeks of storage. Total numbers of S. thermophilus declined significantly (p<0.0001) after 8 weeks of storage in frozen form compared to the capsule. Similar results were observed in L. acidophilus count where no difference was found in capsule form while a significant decrease (p<0.05) resulted in frozen food form. B. longum count was more difficult to determine due to the MRS plate with cystein was not highly selective and specific. L. acidophilus also grows on this plate. The delivery of probiotic in viable form is very important to perform their beneficial effects. Capsulation of freeze dried cells protects the cells during storage condition. The capsulation of freeze dried bacteria seems to offer a more effective way of delivering large numbers of viable cells to the colon as compared to the frozen food format as a vector.