1. The influence of bacteria in different production stages on fermentation
1. Contaminated bacteria during seed cultivation: it is extremely harmful to the entire fermentation process;
2. Contaminated bacteria in the early stage of fermentation: seriously interfere with the growth and reproduction of production bacteria;
3. Contaminated bacteria in the middle of fermentation: interfere with the metabolism of the producing bacteria and affect the production of products;
4. Contaminated bacteria in the late fermentation period: the impact is relatively small.
2. What are the possible ways to cause bacteria in the fermentation tank?
Improper operation of the bacterial culture process; incomplete sterilization of the culture medium; improper sealing of fermentation equipment (such as fermentation tanks, pipes); and unclean air sterilization.
3. What are the types of bacteria that are relatively harmful in different fermentation processes?
1. Fermentation of citric acid, Penicillium;
2. Fermentation of glutamic acid, phage;
3. Fermentation of penicillin, Aerogenes brevis;
4. Fermentation of streptomycin, Brevibacterium gracilis, Pseudomonas;
5. Fermentation of tetracycline, diplococcus, bacillus, and capsular bacillus.
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Fourth, fermentation abnormal phenomenon and analysis of the cause of infection
The abnormal fermentation phenomenon has the following three points:
(1) Abnormal changes in dissolved oxygen: When the bacteria are aerobic microorganisms, the changes in dissolved oxygen decrease in a relatively short period of time until they are close to zero, and cannot rise again for a long time; when the bacteria are non-aerobic microorganisms , And the growth of production bacteria is inhibited due to pollution, which reduces oxygen consumption and increases dissolved oxygen.
(2) Abnormal changes in exhaust CO2: For example, when bacteria are polluted, sugar consumption will increase and CO2 content will increase. After phage pollution, sugar consumption will slow down and CO2 content will decrease. Therefore, the infection can be judged based on the abnormal change of CO2 content.
(3) Other abnormal phenomena: such as poor bacterial growth, abnormal changes in pH, abnormal increase in foam during fermentation, abnormal changes in the color of fermentation broth, abnormal decline in metabolite content, abnormal prolongation of fermentation cycle, fermentation broth Abnormal increase in viscosity, etc. to determine contamination.
Fermentation tank contamination reason analysis:
(1) Analyze the cause of infection from the scale of infection
A large number of bacteria in the fermentation tank: air system. Some fermentation tanks (or tank groups) are infected with bacteria: the seeds may carry germs or incomplete sterilization in the early stage, and may be caused by problems in the intermediate feeding system or the oil pipeline system in the middle and late stages. Continuous contamination of individual fermentation tanks: equipment problems (such as valve leakage or corrosion and wear of the tank body), contamination caused by corrosion and wear of the equipment will cause the contamination time of each batch of fermentation to move forward. Accidental infection of individual fermentation tanks: The reason is more complicated, because various infection methods may cause it.
(2) Analyze from the type of infection
Thermostable Bacillus: Dead corner or incomplete sterilization. Cocci, yeast: may be brought from steam condensate or air. Light green colony (Gram-negative bacilli): The cooling pipe or jacket of the fermenter leaks. Mold: Incomplete sterilization or aseptic operation is not strict.
(3) Analyze from the time of infection
In the early stage of fermentation, the bacteria are infected, the seeds are carried, the culture medium and equipment are not completely sterilized, the equipment or pipelines have dead ends, the middle and late stages of the fermentation, the intermediate feeding, the leakage of equipment, the operation is unreasonable
(4) Reasons for air filtration system
Cause analysis: air inlet, production environment, air filter
Bacteria characteristics: the air filter system will cause the fermentation tank batch to be contaminated with bacteria, and the tank will be contaminated with bacteria. At this time, the air filter system must be tested for aseptic samples
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VI. Inspection and judgment of bacteria in fermentation tank
Sterility test method, microscopic examination method (microscopic examination method), broth culture method, plate streaking culture or inclined surface culture inspection method
Seven. Rescue and treatment of bacteria contamination
(1) Contaminated bacteria during seed culture: Dispose of after sterilization, and carefully inspect and thoroughly sterilize seed tanks and pipes.
(2) Contaminated bacteria in the early stage of fermentation: the nutrient components are not consumed and should be re-sterilized quickly; elsewhere, the necessary nutrients should be supplemented and re-inoculated for fermentation.
(3) Contaminated bacteria in the middle and late stages of fermentation: Appropriate fungicides or antibiotics and normal fermentation broth can be added to inhibit the growth of miscellaneous bacteria; if the content of the product reaches a certain value, it can be placed in the tank as long as it is clearly contaminated .
(4) Treatment of the equipment after fermentation: the empty tank can be heated and sterilized to a temperature above 120°C for 30 minutes before it can be used. It can also be treated with formaldehyde fumigation or soaking in formaldehyde solution for more than 12 hours.
To sum up, since the phenomenon of fermentation tank contamination cannot be avoided, we should improve the level of production technology, strengthen the management of the production process, grasp each link that is susceptible to bacteria, and prevent fermentation contamination as much as possible.