WHEN SCALE UP IS NOT A SCALE UP….

The common term scale up in fermentation technology has been used frequently without really understanding the true meaning of scaling up. This state of confusion has often resulted in studies which are not really scale up but just ordinary fermentation research.
The objective of scaling up studies is to reproduce the same conditions of fermentation efficiency even though there is a great increase in the volume of the fermentor. Scale up is the well planned exercise passing through various stages of increasing volume so as to achieve the industrial production scale with full confidence.
The scale up exercise strictly speaking does not include the stages at the level of inocula development, Petri dish and shake flasks studies. This stage is still considered the preparation or the basic research studies that will ultimately lead to scale up studies
In scale up studies the increase in the volume of fermentors are increased by magnitudes rather than arithmetical increase. But what I have seen in the scale up laboratories or fermentation plant, the type of fermentors used in scale up generally are not designed for scale up! And yet they are very proud in declaring they have a battery of fermentors that can be used as scale up!
IGNORANCE IS BLISS!


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THE STORY OF FERMENTATION

I know this article should have been introduced in the earlier part of this blog. But by doing so I believe I would have succumbed to the normal approach of introducing the subject of fermentation or fermentation technology. This would have made the standard approach boring and the readers of the blog would have thought that there’s nothing new or exciting to learn about fermentation technology.
Instead I have opted to introduce the history of fermentation technology by letting the readers of the blog discover the spread and depth of this topic and to appreciate the subject of fermentation technology less from the traditional history approach but much more from the critical point of view
It is true that the understanding of fermentation technology have its roots far deep in the past or early beginning of human civilization. It should be noted that from the spread of fermentation activities occurring almost in all countries and civilizations, its discovery must have been independent of specific country. It could be considered as more as parallel evolution in the knowledge of fermentation.
Sad to say that despite these observations, there are still some countries or nations which regarded that the fermentation process is their sole copyright in the evolution of human history. If only they realized that the discovery of alcoholic drinks and even fermented food such as fish undergoes the same process with the same microorganisms. The only significant difference is in their naming of the fermented products in the language of their country. Guess the pride of these people is the reflection of their own ignorance of the developments in fermentation in other countries besides their own. (The black age of ignorance of the past is still thriving in the modern minds of the uneducated today!)
The beginning or the discovery of fermentation or fermentation technology is very closely inter twined with ignorance and even religion. There is a general belief in the past that magical forces act to transform the food materials into fermented products. Despite the proof by Pasteur and the wide scientific studies on fermentation today, things have not changed much from the past. There are many human civilizations still believing the presence of forces or spirits to allow fermentation to occur. Even in this modern age the making of certain fermented foods such as tapai or fermented substrate is restricted by the various taboos. If these taboos are broken the fermented food or beverage would not turn well.
There is no such things as taboos to explain the failures but more the problems of contaminations and lack of understanding of the fermentation technology knowledge.
In the Roman mythology they even have honored the fermentation process especially with regard to wine by having a Roman God of wine named as Bacchus. So it is not strange if our own medicine men took to the wine to dance and get into the trance !!
Nothing have changed much from the earlier days of discovery of fermentation to what fermentation is today. The input of engineering and the inventing of the fermentors only help to improve the efficiency of the fermentation process. Strange it may be as in the case of many fermentation products such as antibiotics the many fold increase in the volume or concentration of fermentation products is attributed not so much by the improvement in the design of the fermentors but by the improvement in the fermentation productivity of the strains
In fact the design of fermentors have not changed much from the days of Fleming. Today they are still arguing on the problems of stirrers and impellers…. and rudimentary novel bioreactors.




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FACTORS TO CONSIDER WHEN SELECTING THE MOST SUITABLE STIRRER FOR YOUR FERMENTOR

Most fermentors on the market are generally provided with the Rushton type impeller irrespective of the type of fermentation process carried out and the nature of the fermentation broth rheology. It must be bear in mind that the Rushton impeller is not the universal or standard impeller available. There are many choices of impellers available and the experienced or educated fermentation technologist should have the confidence to choose the right impeller for the right fermentation process
Choosing the most suitable stirrer and impeller system is not easy and one could not rely entirely on the ‘advice’ given by the salesman. He has the job of selling and pushing his products to you and will promise you everything. After all a lot of business is based on deception or the ‘second hand car dealer’ bag of lies
The basics of using stirrers and impellers in a fermentor are to provide mixing and homogenous conditions that will enhance the various mass transfer processes. There are many factors to be considered when choosing the right impeller and stirrer such as speed, power consumption, volume of fermentation broth to even the shape, size and geometry of the fermentor
The objective of any mixing is not to overmixed or undermixed the fermentation broth. Instead the stirrer and impeller should be able to provide a ‘comfortable range’ of mixing where the objectives are met without extreme damages or negative effects to the fermentation process.
This knowledge can only be achieved through experience and sound advice acquired from other fermentor users. But what ever, totally relying on the universal Rushton impeller for all your fermentation mixings is not the right move.


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INTRICACIES OF SCALING UP EXERCISES- THE NAKED TRUTH

As important it is to do scale up exercises in fermentation technology especially for new studies involving new fermentation process or modification of existing fermentation process, the exercise itself is not simple and cannot be executed in one or two simple steps involving one or two parameter studies.
Most fermentation technologists in their first exposure of the scale up exercise would just think just having a few fermentors of different sizes or just monitoring some basic ‘rules of the thumb’ such as tip speed studies they will be able to complete the studies to reach the necessary confidence.
It is far from that, as we know it ourselves that the fermentation process is a very complex process involving various phases that affect the behavior of the microorganisms. IT IS NOT JUST A SIMPLE MATHEMATICS OR ENGINEERING CALCULATION OR EXTRAPOLATION!. It is not easy to achieve the ideal state of trying to reproduce the efficiency of the fermentation process obtainable on small scale studies to at those at larger scale involving several magnitudes in the increment of volume
If we look at the various components in the fermentation process in the scaleup the behavior of the various parameters show different results or behavior. In such a way even before scale up studies are done, detailed studies and understanding of the process of the fermentation must be deeply understood.
The trouble is that most textbooks on fermentation technology seem to present the model of scaling up as being to easy and discussing the topics in such a brief account with a sprinkle of a few formulae
Scaling up understanding are often acquired through real experience and through trial and errors. There is no ‘short cut’ about it. You need to adjust as you go on and to have inputs not only from books but research papers in the journals!
WHO EVER SAYS ITS EASY THEN????


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FERMENTATION SUBSTRATES- THE PRELIMINARY CONSIDERATIONS

The raw materials used in fermentation constitute the substrates for the fermentation process. The substrates could be seen as either the raw materials that will be ultimately transformed into the desired fermentation products or they could be regarded as the source of nutrients for the fermentation microorganisms.
The substrates form the bulk of the fermentation broth and often considered as one of the most important component in the cost of the fermentation products. Thus in order to lower the costs of production the search for the most cheapest and economical source of fermentation substrate will be the top most agenda in any proposed fermentation industry.
The search for the most suitable substrate is not only dictated by costs and availability of the substrate but by other factors such as complexity of unwanted reactions that affect not only upstream, midstream but downstream activities. This would also mean the problem of treating its effluent from polluting the environment
THE RIGHT NUTRIENT COMPOSITION
In most cases the search for the right fermentation substrate or its admixture composition started with the detailed nutrient elemental analyses. Generally a single source of substrate do not have the sufficient composition to fulfill all the requirements as the fermentation substrate and a concocted admixture is often created to make it ‘wholesome’ or complete as the ideal substrate
Some of the recipes of the fermentation substrate is determined or created in the laboratory where the necessary type and concentration of media is determined as if it is a recipe. Experiments and complex chemical and elemental analyses would be carried out by using various analytical methods and its suitability by carrying out nutritional and physiological studies involving petri dish to even small fermentors
After all just having a fermentation media complete with all its composition does not always guaranteed the suitability or success for the fermentation
THE RIGHT SOURCE
The source of the fermentation substrate should be cheap economical and easily available. This is a problem usually involving high volume low cost fermentation process. Pure chemicals though idealistic would send the fermentation costs shooting to the sky! And would not be economically viable unless the fermentation product is high cost and low volume
Such source of cheap fermentation substrate for high volume low cost fermentation has only one possible source that is the unwanted cheap agricultural or industrial waste products. After all to the microbes they don’t see it as dining at expensive restaurant; a food or nutrient is just a source of nutrients or elements
It is of utmost importance that the source of waste products for fermentation is not only cheap but continually available in stable supply. Several alternative sources for contingencies must always be taken care of as good logistics procedure


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CUSTOMISED FERMENTORS?

In the previous blog, I have discussed the design of the fermentor and the concept that there is no such thing as a ‘standard fermentor’ although the various fermentors used almost similar system requirements.
When we say that we are ‘customising’ a particular fermentor it means that the fermentor is designed and built for a specific fermentation process. It is not designed for the use of other fermentation process.
The concept of a standard fermentor means that it is a general fermentor that can be used or modified for various types of fermentation process. The concept of the ‘ standard fermentor’ is to simplify it so that it is easily understood for those who are in their beginning to learn fermentation or to use fermentor in their novice stage.
But as you advanced in your research and understanding of the limitations and capabilities of fermentors you tend to prefer to ‘ customise’ your fermentor so as to provide specific solutions to your problems.
In certain cases of customizing such as in the use of novel bioreactors, the fermentors do not at all looked like the standard fermentor. The use of standard design fermentors would not be able to provide the answers to your problems.
In certain cases, extreme modifications are made in customizing the fermentor.
This is one of the example where issues arise during scaling up or scaling down studies. The exercise is looked as a simple exercise where the use of similar geometry seems to be the easiest way to find the answers. No wonder such studies do not really help or give the accurate answers…….



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AIR IN AUTOCLAVING

The presence of air or gases could be a complicating factor during autoclaving process. The volume that makes up the internal environment of the autoclave is filled with air. Air itself is a bad conductor of heat. So the presence of air in the autoclaving could affect the efficiency of the autoclaving process, unless these air are removed before the start of the autoclaving process.
The removal of air from within the autoclave could be carried out by heating the autoclave until active steaming is carried out. Once this is achieved the valve could be closed and the autoclaving process is started.
What is not often appreciated is that air is not only present in the autoclave but are also present in the spaces of the bottles, test tubes, fermentors and containers to be autoclaved. It is important therefore that this consideration be taken into account.
Sufficient time and heating must be given to drive these air out too or else the parameters for the sterilization cycle be modified if needed.


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