The method to detect the analyse of viable cells of the production strain must be culture-based. Cultivation-independent methods, such as PCR to detect DNA from the production strain, are not acceptable as they are not sensitive enough.
The procedure should enable the recovery of stressed cells. This can be done by using milder and longer incubation conditions. If the strain is known to produce spores, it is particularly important to verify their absence from the product. To prevent overgrowth of contaminating microbiota, selective medium may have to be used, but this must not interfere with the growth of the production strain. Care must be taken also to confirm that the product does not prevent the growth of the production strain. The production strain serves as the positive control to prove the validity of the assay.
Absence of the production strain should be demonstrated from at least 9 g or 9 mL of product without preservatives, taken from at least 3 independent production batches, a total of 9 samples being the minimum. If colonies are found, they are analysed using production strain–specific PCR. If production strain is found from the product, the production process may need to be adjusted.
Biosafe has optimised the method for several types of feed additives, food enzymes and other fermentation products.
Preliminary testing is always carried out to establish proper conditions to be applied during the main test.
To minimize the time and effort during testing, Biosafe asks you details about the test strain and the sample. All information will be kept strictly confidential. The test strain is destroyed after the project.