MICROBIAL CONTAINMENT

When we are dealing with microbial fermentation, we are really dealing with the growth of large number microorganisms in the fermentor. In such situations we are usually faced with two main problems:

1 Preventing the entry of unwanted microorganisms as microbial contaminants into the fermentor which can disrupt the fermentation process. In this situation we are referring to monoseptic fermentation and cultivation of animal and plant cells
2 Preventing the escape of the microorganisms from the internal environment of the fermentor into the surrounding environment. The escape of the microorganisms may occur through process failures or unintentionally. Although in most cases such situation may not constitute any risk as it does not involve pathogenic microorganisms or genetically engineered microorganisms. However, there is still risk which might arise due to the high concentrations of microorganisms released especially in areas in the vicinity of the fermentor or the plant

In the first situation, the prevention of unwanted microorganisms entering the fermentor is often achieved by the process of sterilization and maintenance of aseptic integrity of the fermentation system throughout the period of fermentation.

In the second situation, it is more the prevention of the escape of microorganisms or its destruction of microorganisms released from the fermentor. The released microorganisms do not affect the fermentation process but constitute a safety and health hazard. In the first situation the invasion of unwanted microorganisms will affect the fermentation process rather than being a hazard

In the analyses of microbial containment we must accept the following facts:

1 There is a very high concentration of microorganisms in the fermentor
2 What ever goes into the fermentor must come out, example air, fermentation medium
3 The fermentor is a high pressure vessel

DANGER OF AEROSOLS
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The highest threat in the microbial containment is the air line. Air that enters the fermentor will first have to pass through the fermentation broth containing the billions and billions of microorganisms before escaping through the head space and through the exhaust port. The volume of air passing through the fermentor depend on the pressure and volume of fermentor. Generally about 0.5 to 2 vvm of air is delivered through the fermentor. This will represent a very high volume of air that enters and leave the fermentor throughout the fermentation run all with the potential of carrying along billions of microbes to be released to the environment if not contained

The most common threat of spread of microorganisms from the fermentor is due to aerosols generated. Accidental release of aerosols could result in the widespread transportation and dispersal of microorganisms to the environment by air. Aerosols are easily generated in fermentors due to the presence of surface active compounds, pressurized air and high turbulence.

The existence of aerosols prolonged the survival and spread of the microorganisms due to the mobility of the aerosols and sustenance of the microbes through nutrients present in the aerosols and lower risks of dessication

DANGER OF SPILLAGE AND SPENT MEDIA
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The substrate for the fermentation and the fermentation broth left in the fermentor after termination of the fermentation contains high concentration of microorganisms and raw nutrients which are still able to support the microorganisms as well as microbial contaminants.
Given time and right temperature these microorganisms could proliferate to become a threat to the environment.

It is important that immediately at the conclusion of the fermentation after the fermentation broth is removed for downstream processing that washing,sterilizations be carried out immediately. This will prevent proliferation of the microbes and secondary problems arising from cross contaminations later on

TYPES OF MICROBIAL CONTAINMENT
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There are generally three types of microbial containment in any fermentation facility

1Primary containment
2Secondary containment
3Tertiary containment

Primary containment are activities carried out in the containment of the microbes at the level of the fermentor or bioreactor
Secondary containment are activities carried out at the level of the operator such as protective clothings
Tertiary containment are activities carried out at the level of the laboratory or plant facilities

The level of containment is the reflection of the status of biohazard of the facilities. Those laboratories dealing with very dangerous microorganisms will need the highest level of containment at primary, secondary and tertiary containment level.

KILLING THE MICROBES
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Air or the exhaust gas coming out of the fermentor is the main point of containment control. There are two main approaches to it:

1 Sterilization by filters
2 Killing by heat incineration or disinfectants

Before opting to which choice you will take, one have first of all to consider the physical, biochemical and microbiological characteristics of the exhaust air. Technical and economical constraints to have to be considered as well as the level of biohazards faced



PROTOCOL OF MAINTENANCE OF CONTAINMENT
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Should cover the following:
1 Environmental monitoring
2 Work practices- process protocol, hygiene requirements and clothing, emergency procedures
3 Medical surveillance
4 Worker education and training
5 Engineering controls- physical containment, exhaust gas control,, ventilation
6 Validation of functionality of containment facilities- complete sterilization.physical containment and fermentation termination