Washing and cleaning fermentors seems to be the most mundane and least liked job in fermentation industries. Yet, it is one of the most crucial steps in ensuring that the fermentation process in the fermentors will succeed. It will ensure that is little or no chance of microbial contaminations occurring in the subsequent fermentation process. Yet it is strange to admit that despite the great importance of washing and cleaning on the success of any fermentation run, little considerations are given during the design and implementation stage of the fermentor. Wahing and cleaning are more considered as after thought or at the end of the process.
Washing and cleaning not only show its importance in reducing microbial contaminations and increasing the efficiency of sterilizing the actions of the autoclaving process, but a very efficient cleaning process will cut down the turn around time of fermentors. This means that we can use the fermentors back again and start the next fermentation sooner.
Proper washings not only saves time, money but even labour.
It should be stressed at this early point in the discussion of the subject that, washing and cleaning of fermentors are not the kind of jobs equivalent in restaurants or car wash which could just be executed by almost anyone with minimal education and training. Washing and cleaning of fermentors is a very highly skilled job which requires someone very knowledgeable in microbiology or food technology degrees.
The person trusted with washing and cleaning the fermentors must know:
1 The anatomy of the fermentor, opening and putting back the fermentor
2 Know the materials of the the fermentor and possible side reactions occuring during washing, cleaning and sterilization
3 Know the hot spots within the fermentor which are likely to provide safe haven for the microorganisms
4 Know the use of correct surfactants or chemicals that will give efficient cleaning and toxicity hazards
5 Know how to validify that the cleaning has been effectively carried out by using microbiological testings
The main difference between washings and cleanings in restaurants, kitchens or car washes is that in cleaning fermentors it is just not enough seeing the surfaces clean. A clean surface visually does not guarantee there are no microbial contaminants or redidues from previous fermentation runs!
The effect of poor cleaning of fermentors is costly. You will only realized the full disaster after thousands of litres of fermentation broth is wasted or the fermentation products formed are contaminated.
Washing of fermentors are usually carried out at the end of the fermentation run when the fermentation process is terminated and the fermentation broth is poured out of the fermentor. It is the essential step in preparing the fermentor for the next run. Only after satisfactory cleaning is achieved will the fermentor be sterilized and ready for the next fermentation run.
Poor cleaning will result in remnants of microbes and residues of previous to remain in the fermentor. The presence of these residues have important implications to subsequent fermentation:
1 It provide nutrients for the microbes to grow and proliferate before sterilization process.
2The solid residues will act as a shield or barrier that will prevent effective sterilizations and killing of the microorganisms. It is possible that some of the microorganisms will survive the sterilization process and be a serious microbial threat in the following fermentation
3 The residues will also allow other microorganisms to grow on the remnant broth
4 It is possible that the residues will taint the quality of the next fermentation products by setting of unwanted biochemical reactions
5 These residues will react especially with oxidizing biocides thus reducing the efficiency of the chemical disinfectants.
It is advisable that immediately at the termination of the fermentation run, that the fermentors be washed and cleaned immediately and not to be left in such a septic state over prolonged period. If such actions are not done there is high possibility of the fermentation residues becoming a dried up cake. When this happened more time, energy and chemicals will be needed to clean the fermentors
As we have said earlier washing of fermentors is not similar to washings of dishes in restaurants or in a car wash. A fermentor need to be washed and cleaned in a standard operating procedure to ensure that the fermentors have reached a high level of cleanliness.
CIP AND COP CLEANINGS OF FERMENTORS
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In cleaning and washing fermentors we often come across these two terms; CIP and COP. CIP refers to Cleaning In Place and COP refers to Cleaning Out of Place. In CIP, all the essential cleaning of the fermentors are mainly carried out with minimum opening up of the fermentor. The fermentor is still intact and remaining in place. This type of cleanings are usually carried out for large fermentors such as industrial scale fermentors where it is almost next to impossible to dismantle and rebuild back the fermentor.
In COP, it is usually carried out with small scale laboratory fermentors. Main components of the fermentors are dismantled and cleaned thoroughly. This kind of cleaning is of course more thorough and effective.
In large fermentors CIP is usually carried out by using by powerful steam pressure balls which will give efficient cleaning. This is carried out as part of the cleaning SOP.
Effective washings involve the interactions of the four following parameters
Temperature
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Temperature is critical in increasing the chemical activity of the chemicals used in cleaning and increasing the solubility of solids
Chemical Concentration
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The more concentrated the chemical used for washing the more effective is the reactions
Fluid Motion/Agitation
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Fluid motion and agitation represents the physical and mechanical force that help remove the solids from surfaces
Time
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Time is the essence that allows the contact time to occur between the washing chemicals and cause more effective reactions for better cleaning
SOP FOR CLEANING AND WASHING FERMENTORS
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The effective cleaning and washing usually involve the following steps:
1. Rinsing
2. Chemical Solution
3. Rinsing
4. Chemical solution
5. Rinsing
Routine SOP for washing and cleaning fermentors would probably be carried out in the following steps:
1 End of fermentation, broth poured out fermentor
2 Removal of sensors and electrodes
3 Flushing with water under pressure to remove solids and residues
4 Wash with surfactants thoroughly
5 Wash with water again
6 Rinse with clean water
7 Allow to stand dry before sterilization steps
STERILIZATION AS PRE CLEANING STEP
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It is recommended that sterilization of the vessel with just water inside the fermenter be carried out. This will help in softening or removing hard organic solids at the same time killing the microorganisms still existing in the fermentor
During washings and cleanings it is important that procedures be followed such as:
1 Washing from top to bottom of fermentor
2 Use proper pressure incleaning the fermentors
3 Use the right ph and temperature for washing with surfactants
PHYSICAL CLEANINGS
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It is important during cleaning of the internal surfaces of the fermentor not to scratch the surfaces as it will lead to niches which the microbes will exploit. Do not use hard brushes
USE OF LOW OR HIGH FOAM SURFACTANTS
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There are a wide choice of surfactants and cleaners for cleaning fermentors. Ensure the proper chemicals are used. The use of surfactants are often associated with foams. High concentration of surfactants will result in high foaming which may require efforts and time in removing the surfactants
ENSURE CROSS CONTAMINATIONS DO NOT OCCUR DURING WASHINGS AND CLEANINGS
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Using excessive pressure may generate aerosols and dispersion of microorganisms which might affect subsequent fermentation process
USE VERY CLEAN WATER FOR FINAL RINSINGS
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Two deleterious effects can result from poor quality water. The first is that the chemical cleaning solution may be impacted by the chemicals/ components present in the source water.
The second is that the effectiveness of the rinsing steps may be compromised by contaminants present in the water.
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