The purpose of sterility testing
(1) Monitor whether the culture medium, fermentation tanks and ancillary equipment are completely sterilized.
(2) Monitor whether there are any bacteria invading from the outside during the fermentation process.
(3) Understand whether there are hidden dangers and dead ends of bacterial contamination in the entire production process.
Comparison of various inspection methods
Each of the three methods has its own advantages and disadvantages. The microscopy method is simple and fast, and can detect miscellaneous bacteria in time. However, due to the small number of samples taken for microscopy and the small observation surface of the field of view, it is difficult to detect early miscellaneous bacteria.
The disadvantage of the plate streaking method is that it requires a long time of culture (usually overnight) to determine the result, and the operation is more cumbersome, but it can detect fewer bacteria than a microscope.
Problems in bacterial inspection
The inspection results should be mainly based on plate marking and broth culture results.
Three parallel samples should be done for plate streaking and broth culture.
Three parallel samples should be done for plate streaking and broth culture.
Phenol red broth and plate streak culture samples should be stored until 12 hours after being placed in the fermentation tank, and can only be discarded when determined to be sterile.
Inspection process and time
The selection of production process and time for sample inspection are also very important issues. Scientific and reasonable selection of inspection procedures and times has direct guiding significance for removing materials that have been contaminated by bacteria in fermentation tanks and avoiding further contamination of bacteria in the next process. Sometimes even if the inspection time is long and production cannot be carried out in time, it is indispensable to find out the links that caused the bacteria contamination accident, analyze the reasons for the bacteria contamination, and eliminate the bacteria contamination loopholes in the fermentation tank.
Due to the different strains of products produced, the time to check the fermentation tanks for bacterial contamination is not exactly the same: but the general principle is the same, that is, sampling and inspection should be carried out in each process or after a certain period of time.
In addition to the above methods, in actual production, the presence of bacteria can also be judged based on abnormal changes in parameters such as pH value, exhaust gas, and dissolved oxygen.