A Novel Method for Determination of Sterility of Microcapsules and Measurement of Viability of Encapsulated Organisms

A method of determining the viability of microencapsulated microorganisms (Bacillus Calmette Guerin) is reported. This method was also used to measure the effectiveness of aseptic production of mi-crocapsules in maintaining the interior of the microcapsules free from contamination by microorganisms. This method is advantageous over conventional plating methodology, as plating can only determine external contamination of microcapsules and similar devices. It involves the detection of ¹⁴CO₂, which is generated by the metabolism of ¹⁴C-labeled fatty acid in the growth medium by encapsulated microorganisms. The method depends on the semiper-meable nature of the microcapsule walls, which allows passage of ¹⁴C-palmitic acid and ¹⁴CO₂. BCG organisms encapsulated within an alginate-polylysine-alginate microcapsule (5–15 µm) (1) were shown to be viable, and no contaminating organism(s) was present. Methods suitable for the aseptic production and freeze drying of alginate–polylysine–alginate BCG microcapsules, which retain the viability of the organisms, are reported.