TALKING TO THE MICROBES

The microorganisms in the fermentors or bioreactors are 'talking' to us. But most of us cannot appreciate how they are talking to us! By listening carefully to them, they are telling us whether they are dying, being poisoned, suffering from malnutrition or they are sick and need us to help them.

We as the fermentation technologists must try to understand them by understanding how they talk to us or reading their signals on how they are..The knowledge will help us guide the fermentation process to a successful completion


The most important way the microorganisms are communicating with us is by measuring and analyzing their respirometric data. Respirometry is a measure of their 'breathing'.

Aerobic microorganisms use oxygen in the process of breathing and releasing carbon dioxide as their metabolic products. If the microorganisms are active they will show active respiration by high rates of oxygen utilization

If they are 'sick' or old, they will not respire that actively. If the number of microorganisms are too little so will be the rate of respiration. If the microorganisms are exposed to new or difficult substrate the rate of biodegradation will reflected in their respirometric data

The ability to analyze their respiration must be supported by other data or parameters before reaching the right conclusion

Just like a good physician, a simple stethoscope examination will yield a lot of data regarding the state of health of the patient. To a poor physician the stethoscope will not yield much.... Read more!

LEAF WRAPPED TEMPE VERSUS PLASTIC WRAPPED TEMPE

I am not sure if you have noticed that there is a world of difference in quality of tempe packed in paper and banana leaves compared to tempe packed in plastics?

Tempe packed in leaves wrapping are more flavourful, less compact or dense in the tempe matrix and it is drier.

Tempe packed in plastic are dense and the beans look not properly broken down by the fungi. Worst, they dont really taste like tempe but taste like hard dry soya beans

From the above clues we could argue that in plastic wrapped tempe the following are observed:
1 Higher water detected because of condensation produced by the fungi respiration which could not escaped effectively compared to leaf wrapped tempe
2 Higher water and temperature due to higher metabolism and poor heat transfer from the tempe resulted in very rapid growth of the fungal hyphae or mycelia. This will probably resulted in greated compaction of the hyphal between the beans. The tighter wrapping by the plastic also contribute to the compaction Read more!

CHARACTERISTICS OF FERMENTATION ELECTRODES

Most fermentors at least come equipped with the following electrodes or sensors.
1 Ph probe
2 Dissolved oxygen probe
3 Thermo probe
4 Foam probe
5 Level probe

The ph and dissolved oxygen probes are also commonly used in various laboratories or field monitorings and process controls. The other three probes are more based on the principle of conductance and impedence

Despite the variety of probes such as ion specific electrodes and enzyme sensors present on the market, only ph and DO probes are suitable to be used directly in the fermentor assembly. The failure to incorporate the other electrodes directly into the fermentor is because of the inability of the other probes to withstand the harsh conditions of the fermentor.

The requirements of the probes to be incorporated as probes in fermentors include:

1 Able to withstand high temperature especially during the sterilization process
2 Able to withstand high pressure in the course of the fermentation exercise
3 Maintain aseptic integrity of the fermentor in the incorporation of the electrodes

Only ph and DO probes so far can comply with the above factors and are used routine;y as important online monitoring activities,

The DO and ph probes used in the fermentor are in a way similar to the same probes used routinely in the laboratory. However, they are structurally modified to adapt to the harsh fermentation conditions. They are built of more durable bodies and have specific housings which allow them to be inserted safely in large fermentors.

YOU CANNOT USE NORMAL PH AND DO PROBES USED IN THE LABORATORY FOR FERMENTORS!

ELECTRODE HOUSINGS
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Housings are very important components in electrode sensor systems of the fermentor. Housings allow:
1 the electrodes to be inserted at the correct location in the fermentor.
2 It protects the electrodes.
3It provide defense against contamination of the electrodes.
4It maintains the aseptic integrity of the fermentor system once electrodes are inserted.
5It allows built up of pressure to counter the higher in built pressure of the fermentor


The type of housings for the electrodes depend upon process requirements and the type of electrode/sensor used. Conventional electrolyte filled probes on large fermentors are fitted inside pressurized housings to keep a positive pressure over the fermentors to prevent contaminations of the electrolyte and reduces the risk of plug blockage. Sealed gel electrode provide a suitable alternative




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MONITORING THE FERMENTATION PROCESS

The fermentation process is basically a very complex process. The complexity arises from the interactions of the various components in the fermentation process such as:
1 Microbial component
2 Substrate or feed component
3 Product components

All the components above occurring within the fermentation environment of the fermentor.

The main objectives in any industrial fermentation is to produce the microbial fermentation products in the most optimum quantity and quality within the shortest time possible and in the most economical way.

NARROW BAND OF FERMENTATION OPTIMIZATION RANGE
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This is difficult to achieve or require skill operations. The optimum fermentation conditions that can produce the fermentation products efficiently and economically usually occur within a very narrow band of operating parameters or conditions. If the fermentation conditions deviate slightly then the fermentation conditions will never be considered as optimal. The consequences of this deviations from the optimal operating conditions will often result in:

1 Decline in the volume of fermentation products produced
2 Decline in the quality of the fermentation products

Both these factors will affect not only the productivity of the fermentation process but also in the economics of the fermentation process.

MONITORING OF FERMENTATION
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In order to ensure that the fermentation conditions in the fermentor are always operating under the narrow range of optimal fermentation conditions, the fermentor and the fermentation process must be closely monitored. Monitoring of the fermentation process will include:

1 Visual monitoring
2 Microbiological monitoring
3 Physical monitoring
4 Biochemical monitoring

Of all aspects of the fermentation process especially with regard to substrate input, product monitoring, microbial performance and fermentation operating among others. If deviations from the various parameters occurred, steps must be taken to return it back to the optimum conditions by rectifying the problems. We can therefore say "monitoring" is putting the eyes on the whole fermentation process

TYPE OF SAMPLINGS
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In monitoring the performance of the fermentor and the fermentation process we have to depend on getting information from the fermentation process. These information can be obtained by analyzing or measuring the samples from the fermentation process. The samplings or analysis may be done as:
1 Off line analyses
2 On line analyses
3 In line analyses

These analysis may be carried out by analysing the samples chemically, micro biologically or biochemically. In certain instances the analytical readings may only require simple sensors and electrodes which do not really require removing the samples from the fermentation broth. Modern fermentation industries depends more and more upon electrochemical analyses which not only gives a rapid real time reading but do not intrude or are invasive of the fermentation process. A good example is in the use of off gas analyses using mass spectrophotometers.

Rapid real time analyses are accurate and reflect the real situations in the fermentor at the exact time and place. This will allow immediate remedial actions to be taken compared to previous biochemical analyses in which data may be obtained hours or days after the fermentation process. By then it is already too late to rectify the problems

ADVANTAGES OF MONITORING
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Depending on the speed of the fermentation and frequency of analyses, these measurements can:
1 Improving the process control
2 improving the process yield
3 speeding up fermentation process by controlling rate of nutrients, identifying the important reactions and verifying presence of undesired compounds
4 trouble shooting for the cause of fermentation failures

There are other other parameters which can be monitored to provide clues to the state of fermentation besides the routine parameters commonly used in monitoring fermentation process Read more!

THE HUMAN MOUTH AS A BIOREACTOR

Today we are looking at something close and personal to us; our own mouth or our buccal cavity. But rather than looking at the mouth from the anatomical or physiological approach which interest the dental and the medical profession, we will be looking at the mouth from the point of view as a fermentor or bioreactor.

Many dental researchers in trying to understand the various microbiological and biochemical changes occurring in the mouth have always regarded the mouth as a continuous bioreactor or fermentor. In a way they are right in thinking so as the mouth does show many characteristics of a fermentor with the presence of high concentration of microorganisms and input of nutrients, food and oxygen in the fermentation broth of the saliva. The mouth does its function quite well by providing various micro habitats that support the growth of various types of microorganisms.

However, that is where the similarity ends. In treating the mouth as a bioreactor there is never the real intention in nature to cultivate high concentration of microorganisms as these microorganisms are responsible for various oral pathological problems. Secondly, even though in terms of functions the mouth is a bioreactor, but in its design and structure it differs from the construction of a normal fermentor. It is often the classical mistake of dental researchers in trying to understand the changes in the mouth, they would use normal fermentors to study the happenings of the mouth in vitro rather than in vivo. Although studying in vivo is far more difficult but more meaningful

We cannot say any conclusion based on lab scale fermentors can be really applicable to real understanding of the bioprocesses in the mouth if we cannot come with the accurate bioreactor model of the mouth.It is not good to oversimplify the bioreactor design and try to reach far reaching conclusions

We shall now look at the mouth as a bioreactor from the various points below:

THE VESSEL
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From the point of view of the mouth as a fermentor or bioreactor, it is a vessel or container defined by the lips, cheeks, hard and soft palates, and glottis It is divided into two sections: the vestibule, the area between the cheeks and the teeth, and the oral cavity proper. It is not really well designed in terms of reactor geometry and therefore do not encouraged ideal mixings or circulations of the liquid in the mouth

THE STIRRER
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The stirrer of the mouth bioreactor is the tongue. The efficiency of stirring carried by the tongue is not as efficient as the stirrer in fermentor, as in most times the tongue do not really move actively except when food or drink is introduced into the mouth or perhaps in 'french kissing'

FLUID CIRCULATION
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The endogenous source of fluid in the mouth bioreactor is provided by the salivary glands in the mouth which secretes the saliva periodically by the ducts into the mouth. There is not much saliva produced with the saliva amounting to about 1500 ml daily

The saliva liquid are generally viscous, making the environment rapidly anaerobic unless often oxygenated .

There are two main types of saliva circulation in the mouth:
1 General mixing circulation most times
2 Plug flow circulation periodically especially when swallowing saliva or food bolus


FEED
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The fermentor feed basically consist of food and drinks which we take in through the mouth regularly at intervals. Thus the mouth bioreactor is more a fed batch reactor. However when we are sleeping, there is no input of new feed until breakfast and the mouth will be in the batch mode when we are sleeping

AIR
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Air is taken into the mouth during food and drink intake activities


SOURCE OF MICROORGANISMS
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The mouth as a bioreactor can be considered as a mixed culture septic bioreactor. The source of microorganisms could be introduced naturally and/or formed as natural oral flora of the human body. Sad to say, the mouth is a very dirty and disgusting place where all kinds of decompositions take place

ENVIRONMENTAL AND NUTRITIONAL PARAMETERS
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The mouth is an ideal environment which can support high concentration of microorganisms because it provide:
1 Water
2 Good temperature
3 Food or nutrients
4 Nice ph between 6.5 to 7.5
6 Lots of surfaces for microorganisms to hide and attach such as the surfaces of tongu and teeth
7 mixing for good mass transfer








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ABOUT THESE SO CALLED "HANDS-ON" FERMENTATION COURSES

Recently, I came to chance upon a brochure in the internet about one particular university which will be conducting a 3 day course "hands on" course in fermentation technology entitled "BIOREACTOR OPERATION,MAINTENANCE and TROUBLE SHOOTING"

It is a bit upsetting to me to know that it is quite impossible for the course which is hands on to be given over three days and covering a large number of topics. To make things worst this course is supposed to be "suitable" for engineers and scientists from universities, industries and bioprocessing plants. Throughout my experience for over thirty years in the practical and applied field of fermentation technolgy its impossible to carry out all those studies within such a short time. Unless of course, the course is TOO BASIC OR SIMPLE. If it is be so, then it is no point calling scientists and engineers from universities, research centre and bioprocessing industries. I got a feeling they will know more than the course facilitators knowledge

Fermentation technology is an applied course and you learn it by doing practicals and gaining the experience over long years working with the fermentor. You learn the course by approaching it from apprenticeship more than anything else

I guess, may be the participants are going for the course more a "PAID HOLIDAYS"???? and not to really learn something

Would it not better if the organisers conduct a more narrow and specific course over three days such as "CLEAMING FERMENTORS?" and not to be too ambitious. Read more!

HOW MUCH WORKING VOLUME DO YOU NEED FOR YOUR FERMENTATION RUN?

(PICTURE TAKEN FROM http://www.geocities.com/lesjudith/AlcoholChart/fermenter.gif

In any industrial fermentation, the broth represents the substate that is going to be transformed into the fermentation products. A simple formula is that, more fermentation broth means more fermentation products.

However, in reality the picture is far from the simple truth. Even though most of the fermentation broth will be converted to form the fermentation products, a percentage of the broth or carbon will be converted to form biomass or new microbial cells. As fermentation progresses, you will see the concentration of the substrate will decrease followed with increasing amount of biomass.

In laboratory research using small volume fermentors this rule does not apply directly. The objective of fermentation research differ from production fermentors. Production scale fermentors are large and can take high volume of fermentation broth. There is very minimum impact of withdrawing sample broth from the industrial fermentors for monitoring.

In the case of research or laboratory fermentors, the fermentor capacity is very small sometimes in the range of one litre or a bit more.

In planning how much volume of fermentation broth should be needed to be used by the research fermentor depends on many factors

The total amount of fermentation broth should:

1 At least give a head space volume of 20% of fermentor volume ( not working volume)
2 It should be enough to cover for all sampling requirements needed for analyses throughout the completed fermentation run
3 The minimal volume remaining in the fermentor should at least cover the impeller section for mixing. We cannot have a volume that is less than the height of the impeller
4 After removal of samples for analyses there still should be a residual volume about 40 to 50% volume to ensure the fermentation process is not affected Read more!