SOME VIEWS ON TEACHING FERMENTATION TECHNOLOGY

Fermentation technology is an important subject on the university or college curricula that often sits in the curricula of courses such as chemical engineering, biochemical engineering, bioprocess engineering, biotechnology, food technology, pharmaceutical technology and microbiology.

There are a number of key points in teaching fermentation technology as a subject:

1 Fermentation technology is an applied hands on subject. This means that it is a course which rely strongly on the practical side and involving many hours exposed to working with the fermentor and its ancillary activities
2 This means also that any courses offering fermentation technology must be willing to invest heavily on capital equipments such as fermentors, autoclaves and many down stream activities
3 That there must be an ideal ratio between the number of students per fermentor. The ideal number would be around 4 to 6 students per fermentor. Higher number of students would not ensure each student would have sufficient "clinical experience" with the fermentor.

Fermentation technology is not a subject which the students can learn just by memorising drawings or fermentation processes on a white board or using over head projector. We learn fermentation technology by passing through various mistakes and through experience with the fermentor

There is a requirement of manual dexterity and skill to be trained and acquired by doing the practicals

4 The fermentation syllabus is not merely taking chapters of microbiology, biochemistry or biochemical engineering books. If such an option is taken the it will not make a fermentation technologist out of the student. Selected topics must be taken from relevant fields and wholesomely integrated from the point of view of the interest of the subject of fermentation technology. And to see how this relevant chapters are applied in the course of fermentation technology

The stress on the subject of fermentation technology shall be that at the end of the course the students will not only learn how to run and operate a fermentor successfully but would be able to optimize the fermentation process and carry out trouble shootings and remedial processes for the fermentation system

Field trips to various fermentation industries form an essential components in the teaching of fermentation technology. However, the purpose and the objective of such field trips should not be similar to guided tours conducted by the factories for layman visitors. The students should be exposed to the inner workings of the fermentation industries and the problems and solutions faced right from upstream to downstream activities. There should be brainstorming sessions between the students and the technical or production staff of the fermentation factories. Read more!

PURE CULTURE VERSUS MIXED CULTURE FERMENTATIONS

In the fermentation industry, we normally encounter two types of fermentation such as:
1 Mixed culture fermentations
2) Pure culture fermentations


MIXED CULTURE FERMENTATIONS

In mixed culture fermentations, the fermentation process is considered as septic fermentation and involves more than one species of microorganisms. Generally mixed culture fermentation involves many types of microorganisms for the fermentation process is to complete its fermentation.

The most common types of mixed culture fermentations are always associated with food or even beverage fermentation. In these fermentations, the inocula are usually introduced "naturally" and these fermentations usually show the phenomenon of microbial succession in which different types of microorganisms will predominate as the fermentation progresses. Sewage treatment is also an example of mixed culture fermentation.

Complexity of mixed culture fermentations are usually brought about by the complexity of the substrate composition. The breakdown of the complex substrate require various array of microorganisms to act upon it. In the process of breaking down the complex substrate with the chemistry of the substrate changing and the environmental parameters changing as product of microbial metabolism, certain species are suppressed while certain species will exploit the new conditions


PURE CULTURE FERMENTATIONS
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Pure culture fermentations are fermentations being carried out only by one type of microorganisms throughout the fermentation process. Of course in nature pure culture fermentations rarely occurs as there are always the presence of many types of microorganisms in nature and that inter species competition is a very strong force to contend with.

Pure culture fermentations are only carried out by the fermentation industries interested only in obtaining fermentation products of that particular microorganisms and not others.

In fact the presence of other microorganisms in the fermentation is actively prevented and these unwanted microorganisms are called as microbial contaminants which can affect the desired fermentation process negatively.

As we have said earlier here, pure culture fermentations in nature is not normal or usual. In order for the industrial fermentations to carry out pure culture fermentations, they have to carry out certain steps such as:

1) Obtaining pure culture or strains of the desired microorganism
2) Build up sufficient biomass for the fermentation process of the desired microorganism
3) Prepare sterile media that can only be inoculated by the desired microorganism
4) Prevent the unwanted entry of any other undesired microorganisms throughout the fermentation process, from upstream, right down to downstream processing

Aseptic techniques and maintaining stringent aseptic integrity of the fermentor and the fermentation system is essential for the success of the pure culture fermentations Read more!

CHARACTERISTICS OF MICROBIAL CELLS AND FERMENTATION

The type of fermentation carried out will also reflect the type of microorganisms or even cells that are used in the fermentation studies. Different microbes and different cells used in the fermentation will affect the choice of the most suitable fermentor for the studies. Thus the physical characteristics of the cells,its physiology will have to be considered in choosing the right fermentation system for the fermentation studies.

The golden rule of fermentation is simple:

MICROORGANISMS WILL AFFECT THE FERMENTATION PROCESS AND FERMENTATION PROCESS OR THE TYPE OF FERMENTORS USED WILL AFFECT THE PHYSIOLOGY OF THE ORGANISMS

As we said earlier the choice of microorganisms is diverse to be used in the fermentation studies. Bacteria, Unicellular fungi, Virus, Algal cells have all been cultivated in fermentors. Now more and more attempts are tried to cultivate single plant and animal cells in fermentors.

It is very important for us to know the physical and physiological characteristics of the type of cells which we use in the fermentation as we will know the limitations and optimum conditions for us to operate the fermentor.

BACTERIA
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These unicellular microorganisms are often used in various fermentation. They are procaryotes and do not show presence of membrane bound organelles. The bacteria are very microscopic particles when compared to protozoa, algal, fungal and plant and animal cells.

One of their most unique physical characteristics is that they have very strong cell wall and very high internal osmotic pressure. These factors make the bacterial cells very strong and thus they can with stand strong shear forces emanating from the shear action of the impellers and intense liquid circulations

Due to their very small size they do not really get "entangled" or spliced by the shearing blades of the impellers and will be carried away by the flow of the broth circulations

FUNGI
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When we talk about fungal fermentation using fermentors, we are specifically referring here to unicellular yeasts or those simple hyphal fungal sich as actinomycetes or streptomycetes.

These unicelluar fungi are eucaryotes and are clearly larger compared to bacterial cells. The yeasts are small and occur unicellularly and they have very strong cell walls which protect them against the shear forces within the fermentor.

In the case of streptomycetes and actinomycetes they occur more as filamentous or hyphal morphology At such under fermentation mixing by the impellers there is great tendency for cell or filamental breakages to occur, as their cell walls are rigid

PROTOZOA
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Protozoa are unicellular animal cells and are eucaryotes. They have larger cells and they really do not have protective cell walls. Strong mixing or shear forces such as by the use of impellers will easily damage the cells

ALGAE
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Algae used in the fermentors are large unicellular plant cells. They have very strong cell wall. However these strong cell walls are rigid and are easily damaged by the impellers and shearing forces generated

VIRUS
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The most microscopic of all cells and are therefore not affected by the shearing forces Read more!

CHOOSING THE RIGHT FERMENTOR FOR YOUR NEEDS!

There are many types of people who are interested in carrying out different fermentation studies, and there are as many types of fermentors available from the market. It has never been a simple and easy choice to choose and buy a fermentor for your needs. Sometimes buying a fermentor is akin to buying your first car...you might in the end concluded you bought the 'wrong' fermentor based on your inexperience and wrong advices given by your so called ' fermentation expert ' colleagues!

There are several factors that influence in the choice of your fermentor;

1 PRICE
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Fermentors are generally very expensive capital equipments. A good simple laboratory fermentor easily costs as much as a small car! So, unless you have a lot of money to spend it's better to buy a fermentor that is within your economic range but still able to fulfil your fermentation needs. Big and sophisticated fermentors or famous branded fermentors are expensive.

So if your money is quite a limiting range it is better to go for a standard fermentor that is equipped with the basic sensors and controllers. Do not go for the advanced andmore sophisticated range. Even though it is more impressive but the additional benefits is not worth the extra costs!

Go for the well known reliable brands that is widely used in various laboratories and do try to get the comments about that brand from other users of the fermentor. Personally, I have always been impressed by the New Brunswick fermentors which in my opinion are good value for money and they are the reliable 'work horses' of fermentation.

Somehow I have always have preferences for the analogue controlled fermentors compared to the digital automatic advance models. I mean things are fine with the advanced fermentor models until breakdown sets in.

SIZE OF FERMENTOR
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The general rule about fermentor is that the bigger the fermentors, the more expensive they are. Of course it is unavoidable to buy large fermentors for pilot scale and production scale fermentation. If however, we are intending to do basic research or for teaching, the fermentors recommended should be small fermentors of 5 litres capacity or less. It is more easy to manipulate and cheaper to operate.

I find that there is no difference in the results of fermentation studies carried by fermentors of 2 litres to 10 litres study. In fact by using larger fermentors we need to use more fermentation media, aeration compared to using smaller fermentors.

It is far more better instead of investing in one large fermentors we opt for a number of smaller identical fermentors. At least we can do variation experiments or replicates within the same time!

TYPE OF FERMENTATION TO BE CARRIED OUT
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Most fermentors offered in the market are basically the "standard" design or called the Continuous Stirred Tank Reactor or CSTR . These CSTRs are usually in the form of cylindrical tank equipped with a stirrer with standard electrodes such as ph, dissolved oxygen and temperature probes. It is usually equipped with air spargers.

These CSTRs are more designed for general aerobic fermentation as indicated by presence of spargers and dissolved oxygen probe. It is also meant for pure culture fermentations reflected by its strong aseptic design.

This model is not specific for anaerobic fermentation or those involving open and septic fermentations.

This is not trying to say that these fermentors are unsuitable for anaerobic or septic fermentations. It merely means that using these fermentors is a waste of extra costs incurred as they are not required. Perhaps it only makes the manufacturers and sales people happy!

FERMENTORS FOR RESEARCH AND TEACHING
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Fermentors used for research and teaching normally consist of small size bench top fermentors with working volume of between 2 to 5 litres.

Teaching fermentors are usually small fermentor with the basic sensors such as ph, temperature and dissolved oxygen probes. Usually these fermentors are sterilized in autoclaves as they are not often equipped with in situ sterilization facilities. They are usually with glass body and maybe with a stainless steel top plate

Research fermentors are about the same as the teaching fermentors but they may be bigger of up to 50 or even 100 litres capacity. Usually research fermentors consist of a range of fermentors of various sizes to accomodate some basic scale up studies.

Research fermentors may be equipped with additional probes and sensors

COMMON MISTAKES IN BUYING A FERMENTOR
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One of the most common mistakes in buying a small fermentor with non ' in situ' sterilization facilities is that no considerations are given for suitable autoclave provisions for the fermentor. Some discovered to late that they have bought fermentors that could not fit the autoclave chamber! Or that the fermentors can only fit the autoclave only by doing physical calistenics for the fermentor in order to fit the autoclave! This is dangerous and might result in poor sterilizations of the fermentor

(MORE WILL BE DISCUSSED IN SECTIONS ON FACILITIES FOR FERMENTATION LABORATORY/PLANT) Read more!

HAZARDS IN A FERMENTATION LABORATORY OR PLANT

Have anyone of you tried visiting a fermentation factory or plant? If you have you will know the experience....

Huge fermentors that stretch from the floor almost to the ceiling
High over head gantries
Humid and warm environment
Noisy with all the steam hissing sounds
Motors everywhere

Sometimes it looks as if these fermentation laboratories or plants are located in workshops, with tools and skids everywhere..

It is a dangerous and hazardous place to be and safety precautions are of the utmost. Accidents do easily happen here if no precautions are taken.

The type of hazards that might occur can be classified into the following areas:

1 Microbiological hazards
2 Physical hazards
3 Chemical hazards
4 Electrical hazards

MICROBIOLOGICAL HAZARDS
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In the fermentation industries or laboratories, we are dealing and always exposed to very high concentrations of microorganisms. If taken care and proper control these high concentration microorganisms are always contained in the bioreactor where they are purpose grown.

Depending on the type of fermentation process, the microorganisms used may or may not be pathogenic. Any danger of release of pathogenic microorganisms would be a real threat to the surroundings

The risk of mirobial hazards can occur at all stages of the fermentation activity right up from upstream, mid stream and down stream. Of course the most crucial stage will be the period the microorganisms are grown in the fermentor. There are billions and billions of microorganisms "swimming" in the fermentation broth!

Microorganisms can only escape due to poor handling procedures that is poor microbiological techniques. They can also be released by accidental discharge or poor containment of the microorganisms in the fermentor

In aerobic fermentors, air or oxygen is actively supplied into the broth of the fermentor for the use of the aerobic microorganisms. Most of the air will be released through the exhaust outlet to the environment. If the exhaust air is not sterilized or filtered, there is the danger that aerosols carrying the microorganisms from the fermentor will be released.

The fermentor is usually operated skightly under high pressure of about two bars. Any sudden release of the pressure through any of the valves risk releasing and spreading the microbes.

The presence of aerosols released from the pressured fermentor will exacerbate the problem of microbial dispersion and transmission. Not only will the aerosols be the " carrier" for the microbes but it will even protect the microbes from premature dessication and even provide nutrients for the microbes

Microbial containment should be of the highest order in managing pathogenic bacterial and viral fermentation

CHEMICAL HAZARDS
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There are a few possible chemical hazards that may arise in operating the fermentor or in the fermentation plant. Chemicals that may be used in the fermentation plant are from a few sources"

1 Calibration gases
2 Gases used in fermentation such as nitrogen, oxygen, hydrogen, carbon dioxide, NH3 gas
3 Solvents such as alcohols
4 Surfactants
5 Chemicals used as substrates
6 Acids and alkalies
7 Disinfectants

Some of these chemicals are toxic, flammable, corrosive and may be dangerous if not used properly

PHYSICAL HAZARDS
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Physical dangers that lurked in the fermentation laboratory or plant may include:
1 Heat
2 Pressure
3 Slips and falls
4 Knocks
5 Fire and burn hazards
6 Cuts and bruises

Dangers from high heat source occur in such activities as sterilizing the fermentors or from the use of autoclaves.
High pressure accidents too can occur by improper use of fermentors and autoclaves

Slippery fermentation plant floors could easily lead to slips and injuries. Cuts and bruises are common during handling of the fermentor

Equipments and tools left haphazardly could lead to unwanted accidents and falls

Improper use of flaming during aseptic procedures could lead to accidental burnings and personal injuries

ELECTRICAL HAZARDS
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Electrical accidents such as electric shocks is common in any fermentation laboratory. Short circuits are common. High voltage and high amps current are often used regularly in the fermentation operation

Fermentation operatives should be trained to identify all the possible danger points and steps taken should accidents happen. This will be discussed in future blogs Read more!

ARE WE "UNDER USING" OUR FERMENTORS?

It seems it is the fashion nowadays that every biotechnology, microbiology, bioprocessing and chemical engineering laboratory would not want to be seen without having fermentors in their laboratories. Fermentors or bioreactors seemed to represent 'memberships' to the exclusive TECHNOLOGY CLUB. You will be highly regarded if you have fermentors in your laboratory! It does not matter if you are not operating it properly or under operating it! Most just regard by having fermentors in one's laboratory will AUTOMATICALLY qualify oneself as a fermentation technologist

Many know only how to start, monitor and terminate the fermentation process. They however do not know how to use the fermentors to fulfill their intended research or how to fine tune the fermentors to bring their fermentation research in the most economical, efficient way as to yield the most meaningful data. As a simple example, many would not know just how much fermentation broth would be needed for a correct fermentation run? There are the greedy researchers who would fill their fermentor to the brim short of over flowing. Then there are those who use very large fermentors just to carry out a small bench type of studies!

In reality most are not trained to run the fermentors properly or be creative in the use of the fermentors for research or solving industrial problems. In most cases these fermentors just become expensive ' white elephants' that adorn their laboratories! Read more!

MATERIALS FOR FERMENTORS

As previously discussed, fermentations can be carried out in any vessel or containers. The only limitation of such vessels is that the fermentation process will not be efficiently carried out as those carried out in specially designed and built bioreactors.

When we build or buy fermentors it is important to know the roles and the choice of materials that go into a fermentor. This is especially so when we carry out fermentation process that are fastidious, require high sanitary requirements and can withstand all the demanding requirements of the intended fermentation process.

A typical fermentor today is made up of various materials which will confer certain advantages or disadvantages to the fermentor and to the fermentation process. The strength and function of a fermentor depends on its weakest link or the weakest material!

GLASS
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Glass to be used in building a fermentor have certain beautiful as well as poor characteristics.

It's positive attributes are that the glass material is inert and do not react with the components of the fermentation broth. Glass make ideal materials for us to observe directly the fermentation process that is occurring in the fermentor.

The bad thing about glass is that glass easily breaks. We cannot build large industrial fermentors using glass alone! Of course there are tempered glass but still they are not suitable to build large fermentors. In most large fermentors, glass are only used as observation windows or ports. Only small fermentors can be build using glass body.Glasses that are used in building fermentors are usually the strong type of glass which are not easily broken. These glasses are called boro-silicate glass

Glass as a material show poor heat conductivity which becomes a problem during mass transfer of heat between the contents of the fermentor and the surrounding environment



STAINLESS STEEL
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Presently stainless steel are very popular materials to build the fermentor. It has a number of positive attributes that is ideal to considered as the main material to build fermentors. The only bad thing about using stainless steel in building fermentors is that its costly!

Stainless steel are strong, robust and durable. It is inert and do not react with chemicals or contents of the fermentors. It does not rust and lasts a lifetime. It shows good heat conductivity which is ideal in fermentation operation

Stainless steel can be easily can easily be produced in sheets to build very large fermentors by welding the various plates

RUBBER and PLASTICS
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Rubber and plastics are polymers which show characteristics like compressibility, deformation and inert properties. They make good seals between two pressed surfaces to ensure tight fit and maintain the integrity aseptic conditions and prevent leakage.

Rubber and plastics such as tygon tubings are excellent for for various supplies of air and chemicals to the fermentors.

All these rubber and plastic stoppers can withstand continuous and frequent sterilizations

They are also good insulators for various electrodes and sensors

GREASE and LUBRICANTS
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Special kind of grease or lubricant are often used as part of the fermentor operation. Grease are used not only to seal tight the flanges but also as part of the mechanical seal encompassing the stirrer shaft. The grease are usually viscous and can withstand vacuum pressure


COMPOSITE FERMENTORS
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Most fermentors are made up of using various materials as stated above. All these different materials show different physical and chemical properties such as exhibiting different coefficient of expansions under different temperature during heating and cooling of the fermentors. Considerations must be taken in adjusting the requirements to ensure that the fermentor will function properly

Care must be taken to see the ' expected lifetime' of each component material especially those components made of rubber and plastics. They need to be examined periodically for wear outs and defect and replaced to ensure that the fermentation will be successful


ARE WE OVER DESIGNING OUR FERMENTORS?
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Specialized factory built fermentors are expensive and represent a huge capital investment! Can we still have fermentors that are cheaper using cheaper materials? There is no law saying that we cannot have cheaper fermentors

It all depends on the type of fermentation process we are trying to run and the lifetime expected of the fermentors.

Although the use of stainless steel is popular but at the same time it is very expensive. We use stainless steel as fermentor components more from the point of sanitary requirements especially if we are fermenting pharmaceuticals or food. If we are fermenting other non sanitary demanding fermentors then we can go for other materials options

The good thing about stainless steel fermentors is that we can always adapt the fermentors for other types of fermentations should we decide to change.

It is sad most imagine only the continuous stirred tank reactor as THE FERMENTOR. Many fermentations can be runned using other variations of fermentor such as fibre glass and high density plastics.( Here, you need the prior advice of a fermentation consultant first!) Read more!

DESIGN OF BIOREACTOR

(PICTURE TAKEN FROM WWW>BIOREACTORDESIGN.ORG) AND WWW.CEBTECHSERVICES.COM)


In the first place there is no "hard and fast rule" that fermentation could not be carried out in any vessel or container. You can carry out just about any fermentation process in any vessel from bottles, plastic buoys, tin cans and even test tubes! What fermentation process occurring in the test tube will still occur in the bioreactors!The only problem in using these various types of vessels to carry out the fermentation process, the fermentation process might not be efficiently carried out and might be prone to contaminations and other safety hazards.

In the initial stages of design and construction of a fermentor we have to ask ourselves:
1) How to optimize the conditions that will allow the bioreactor to support high concentration of microorganisms?
2) What sort of fermentation is our fermentor operating for?

A good bioreactor that is designed to support the growth of high concentration of microorganisms must be able to:

1) Provide a good mixing system to ensure that physical, chemical and microbiological conditions are homogenous inside the fermentor. We must ensure that every microorganism in the fermentor will be exposed to a good supply of nutrients and oxygen( for aerobic microorganisms only) and other physical chemical parameters. A good mass transfer is the main requirements in the design of fermentor

2) The geometry design of the fermentor should be a tall cylinder which not only encourages good mixing and transfer of oxygen but good circulation of the fermentation broth. One of the main parameters that influence the efficiency of mass transfer of oxygen is the path of theoxygen and time in contact with the broth.

The type of fermentation to be carried out will significantly affect the type and design of the bioreactor.

Aerobic fermentations differ in their requirements from anaerobic fermentation.
Solid substrate fermentation differs in requirement from liquid substrate fermentation.
Mixed culture fermentations differ from pure cultures fermentation. In pure culture fermentations, there is a stringent demand for aseptic conditions compared to septic fermentations. Read more!

CONCEPTS OF A BIOREACTOR

(PICTURE TAKEN FROM WWW.NIROINC.COM)

For this blog, we will discuss in a preliminary way on what really is a bioreactor or a fermentor. In industrial fermentation technology, our goal is to produce high volume of fermentation products which will be industrially or economically viable. This means that we have to produce sufficienr fermentation products such as metabolites, enzymes, pharmaceuticals or biomass that is economically viable. In any industry, there is an economy of scale, so that production is technically and economically viable for the market.

As we have previously discussed, one or just a few microbial cells would not be able to produce significant amount of products. To be industrially viable we must produced tons or even thousands of litres of the fermentation products! In order to do this we have to grow or cultivate high amount of microorganisms... billions and billions of microorganisms to effect the production of enough fermentation products for the market.

It is not easy to produce billions and billions of microorganisms and thousands of litres of fermentation products. Under laboratory conditions or at the level of the hobbyists which deals with just a few litres of fermentation broth, things are simpler and easier to facilitate. At the level of industries we need bigger facilities which can produce the fermentation products.

To achieve this objective, fermentation industries need the use of fermentors or bioreactors that can support the growth of very high concentration of microorganisms. A bioreactor or a fermentor is not just any simple vessel that can hold large volumes of fermentation broth. It is more than that!.

A bioreactor is a specially designed vessel which is built to support the growth of high concentration of microorganisms. It must be so designed that it is able to provide the optimum environments or conditions that will allow to support the growth of the microorganisms.

Before designing the vessel, the fermentation vessel must fulfill certain requirements that is needed that will ensure the fermentation process will occur efficiently

1 The vessel should be robust and strong enough to withstand the various treatments required such as exposure to high heat, pressure and strong chemicals and washings and cleanings
2 The vessel should be able to be sterilized and to maintain stringent aseptic conditions over long periods of the actual fermentation process
3 The vessel should be equipped with stirrers or mixers to ensure mass transfer processes occur efficiently
4 It should have sensors to monitor and control the fermentation process Read more!

FERMENTATION PRODUCTS

(PICTURE TAKEN FROM WWW.BIOS.NIU.EDU)

The diversity of fermentation products produced by the microorganisms is a reflection of the metabolic diversity of the microorganisms used in the fermentation process. Many fermentation books classify the fermentation products into four basic groups:
1 Primary metabolites
2 Secondary metabolites
3 Biomass ( or production of microbial cells)
4 Bioconversions , which in fact is not a product but a microbial transformation activity

PHYSICAL LOCATION OF FERMENTATION PRODUCTS
We can locate these fermentation products physiologically or physically with respect to the microbial cell. Physical location indicates the exact location where the products are formed or accumulated. Such products may be intracellular or extracellular or it maybe excreted into the fermentation broth.
1 Intracellular products may be in the cytoplasm or in the organelles.
2 Extracellular location may occur as deposition outside the cells of the products secreted. Exopolysaccharide and extracellular enzymes are fermentation products located out side the cell.
3 Secreted fermentation products are released by the cell into the broth after they are formed. Most of these secreted products are soluble metabolic waste products such as alcohol.

The physical location of the fermentation products us important in determining the ease or difficulty of extracting and concentrating the products during downstream activities

PHYSIOLOGICAL LOCATION OF FERMENTATION PRODUCTS

There is another way of looking at the fermentation products, that is by the physiological location of the fermentation products. In physiological location of fermentation products we look at the formation of the products as function of the microbial growth curve. Certain fermentation products are formed throughout the growth of the microorganisms while there are other fermentation products formed only at the onset or during the stationary phase.

Primary metabolites and biomass are maximally produced at the log phase of the growth curve. Antibiotics and secondary metabolites are only produced at the onset of the stationary phase Read more!

ROLE OF MICROORGANISMS IN THE FERMENTATION PROCESS

Initially, it might be hard to imagine how microorganisms contribute to the fermentation process. How can such small and microscopic cells unseen to the naked eyes produce such high volumes of products? How can such microorganisms produced such a rich diversity of fermentation products which are useful to human beings?

The answer to the first question is simple enough. One tiny microscopic microbial cell will not produce industrially significant volume of fermentation products. However, when we talk about billions and billions of microbial cells in the fermentation vat, the volume and concentration of fermentation products is industrially and economically significant!

The diversity of fermentation products produced by the microorganisms is attributed to the rich diversity of microorganisms which have a diverse metabolisms that can yield various types of fermentation products

WHY MICROORGANISMS ARE THE BEST CHOICE FOR FERMENTATION?

The success of using microorganisms for fermentation lies in their very microscopic and metabolic characteristics. It is good being small!

1 High surface area to volume ratio

Microorganisms are very very tiny creatures. Taking an example of a rod bacterium (imagine a brick!), we can see that it has six free surfaces that surrounds the bacterium. These six free surfaces interfaced with the surrounding environment from where they obtained their nutrients or to where they throw away their metabolic waste products.

With such a high number of free surface areas in a tiny volume of cell, it confers upon the bacterial cell a very high surface area to volume ratio. This very high surface area to volume ratio allows maximum or optimum surfaces for diffusions or molecular exchanges to occur between the microbial cell and the environment. No matter where the molecules are, they are easily accessible for diffusion into the microbial cell.

Compare this with the elephant which is such a huge animal. which has a very low ratio of surface area to volume ratio! If nutrients are to diffuse through the surface area of the elephant it would not be enough to supply every cell of the elephant!

Once the nutrient molecules diffuse through the cell wall and membrane, it can be easily transported to where its needed in the cell. The size of the cell is so microscopic that distance covered in the transportation of the molecules in the cell is a convenience!

With such an ease of diffusion of nutrient molecules from the environment into the cell, and the diffusion of waste products from within the cell outwards to the surrounding environment we can see that metabolism will be at optimum state.

The efficient nutrient uptake coupled with the small size of the cell will allow for rapid synthesis and reproduction of new cells. Microorganisms under ideal state will double up within hours. Animals like elephants and human may take months to reproduce themselves.

2 Mode of nutrients transportation

The nutrients which diffuse into the microbial can either use simple diffusion process which is powered by the differences in the concentration gradients between the environment and within the cell. For very small nutrient molecules, most would diffuse by the mechanism of passive diffusion. Larger and complex molecules use active or group transport which requires expansion or utilization of energy

Microbes easily reproduce asexually! There is no real need to have a opposite partner cells, get married and reproduce. They will just as easily split their cells into two daughter cells which will later grow into larger cells and repeat the cycle...



3 Genetic adaptability

Microorganisms generally show the ability to adapt to new environment. They can get easily adapted to living under different environmental conditions and also adapting to new sources of carbon or substrate. This ability is the result of various genetic adaptation which selects "successful" strains through mutation and genetic recombination. Some of the bacteria are even equipped with plasmids which can synthesize new enzymes that help the microorganisms exploit the new environment. The very short generation times and the high population generation will aid the selection and recombination process.

4 Metabolic diversity

The unique thing about microbes are their metabolic diversity shown by various members of the microorganisms. They have the ability to use different energy sources and to use different types terminal electron acceptors

Their ability to use different substrates is also correlated with the microbes ability to produce a diversity of fermentation products Read more!

THE STUDY OF FERMENTATION TECHNOLOGY

Fermentation Technology could be defined simply as the study of the fermentation process, techniques and its application. Fermentation should not be seen merely as a process that is entirely focussed on the happenings occurring in the fermentor alone! There are many activities that occur upstream leading to the reactions that occur within the bioreactor or fermentor, despite the fermentor is regarded as the heart of the fermentation process.

Upstream activities cover such activities such as:
1 Isolation and screening of microorganisms
2 Physiological studies on the microorganisms for optimize groth and maximum products formation
3 Nutritional and media studies
4 Amplification of cultures
5 Scaling up studies

Mid stream activities cover the control and optimimization of activities that occur within the central fermentor itself
1 Monitoring the various physical and biochemical parameters for optimum fermentation

Downstream activities cover activities immediately after the fermentation process in the fermentor is completed and starts with the broth withdrawal and the extraction, purification and concentration of the products.
During downstream activities it involves more bioprocessing and chemical engineering unit processes.


Fermentation technology is the whole field of study which involves studying, controlling and optimization of the fermentation process right up from upstream activities, mid stream and downstream or post fermentation activities.

The study of fermentation technology requires essential inputs from various disciplines such as biochemistry, microbiology,genetics, chemical and bioprocess engineering and even a scatter of mathematics and physics! Read more!

WELCOME! YE FERMENTATION LOVERS

This blog is created for those people out there who are interested in the field of fermentation. This blog is open to both novices and specialists in both applied or non applied fields of fermentation. To many, the term fermentation is synonymous with the production of fermented beverages and food. In reality the field of fermentation covers diverse activities that affect our lives in many ways.

This blog will hopefully bring together all the various parties interested in understanding fermentation and will be the forum among all fermentation lovers.

EARLY UNDERSTANDING OF FERMENTATION

Historically the subject of fermentation is interesting and the understanding and definitions of the fermentation process changes with time.

In the beginning fermentation is discovered accidentally by our ancestors when they discovered that food left accidentally in vessels showed no signs of deterioration and instead the food is preserved. They also found out that these preserved foods have undergone physical and biochemical changes that are somehow very pleasing to them.

Of course during those ancient times when knowledge about the science and the roles of microorganisms were unknown. Our ancestors then attribute the changes occurring during the fermentation to the work of spirits, magic and others. This was the period where "ignorance" ruled the day and the theory of spontaneous generation was the popular theory to explain the changes that occurred during the fermentation process

What is interesting during that early period of fermentation discovery, our ancestors observed that the process of fermentation is always associated with the generation of gas bubbles in the fermentation liquid. The observation mimics the boiling of water and thus the first definition of fermentation is associated with term "fervere" which is Latin meaning "boiling"

Fermentation then was an art and not a science! Good fermentation skills were developed as an art and handed down from one generation to the next. Even till today the archaic traditional food and beverage fermentations are still carried out in homes and cottage industries. Wines and fermented foods are good examples!

FERMENTATION PROCESS AS A SCIENCE

The next important step in the understanding of the fermentation process occurred many years later when Pasteur did several experiments and concluded that the fermentation processes are mediated by the activity of microorganisms such as yeasts. Pasteur helped in " demystifying" the process of fermentation from the status of witch crafts and placed it in the realms of science. The microorganisms which carried out the fermentation processes are anaerobic microorganisms which can live in the absence of oxygen. These anaerobic microorganisms obtained its energy by breaking down the sugars to form alcohol

FERMENTATION IN TERMS OF BIOCHEMISTRY AND PHYSIOLOGY

The next step in understanding the fermentation process occurred quite recently when scientists get together and characterized the fermentation process. Fermentation is now defined as a process of energy generation by various organisms especially microorganisms. The fermentation process showed unique characteristics by which it generate energy in the absence of oxygen. The process of energy generation utilizes the use of substrate level phosphorylation (SLP) which do not involved the use of electron transport chain and free oxygen as the terminal electron acceptor.

SLP is a unique mechanism shown by certain anaerobic microorganisms which allow these microorganisms to occupy niches which were once thought not possible to support life.

The drawback in this energy generation system is that very little amount of energy can be produced compared by using aerobic respiration involving oxygen as the terminal electron acceptors.

In SLP both the electron donors and acceptors are all organic intermediates!

ENGINEERS DEFINITION OF FERMENTATION

It is only up to recently with the rise of industrial microbiology and biotechnology that the definition of fermentation took a more less specific meaning. Fermentation is defined more from the point of view of engineers. They see fermentation as the cultivation of high amount of microorganisms and biotransformations being carried out in special vessels called fermentors or bioreactors.

Their definitions make no attempt to differentiate whether the process is aerobic or anaerobic. Neither are they bothered whether it involves microorganisms or single animal or plant cells cells.

They view bioreactors as a vessel which is designed and built to support high concentration of cells.

IS IT FERMENTERS OR FERMENTORS?

These two terms "fermenters" and "fermentors" are often used freely in most fermentation literature. Strictly speaking it is not the difference of English or American glossary! Fermenters refer to the microorganisms that carry out the fermentation process and fermentors refer to the vessels or bioreactors in which support the growth of the microorganisms.

UNIVERSALITY OF FERMENTATION

It is quite surprising that traditional fermentation activities such as the fermentation of food and beverages start early in the cultural history of mankind. Many countries have sort of independently discovered the fermentation process and have produced their own type of fermented food and beverages. The method used in the fermentation is similar or identical. It is only the diversity of substrates used for the fermentation differ to produce the different types of fermented foods and drinks. Each country or civilization will use the substrates indigenous to their own country. Read more!

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A Malaysian nationality with over 30 years experience in teaching, research and industrial consultancies related to the field of Industrial Microbiology and Fermentation Technology

Currently a consultant specializing in Trouble shooting, Diagnostics and Optimization of various fermentation processes in various industries. Available as expert witness in wastewater environmental litigation and industrial microbiology

Email: boulevardgumbo (at) gmail (dot) com
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