Fermentation Technology

Fermentation Technology

Definition

Fermentation is a metabolic process which normally involve complete living cells (microbe, mammalian or plant), as the biocatalyst, and will aim to bring about specific chemical and/or physical changes in biochemical materials.

The controlled use of microorganisms, cells, or cellcomponents to make a specific product.

Advantages of fermentation technology

1. Complex molecules such as proteins and antibodies cannot be produced by chemical means.
2. Bioconversions give higher yields. complex product mixture requiring separation.
3. Biological systems operate at lower temperatures, near neutral pH, etc.
4. Much greater specificity of catalytic reaction
5. Can achieve exclusive production of an isomeric compound

Disadvantages of fermentation technology

1. Can be easily contaminated with foreign unwanted microorganisms, etc.
2. The desired product will usually be present in a complex product mixture requiring separation.
3. Need to provide, handle and dispose of large volumes of water
4. Bioprocesses are usually extremely slow when compared with conventional chemical process.

Types of fermentation

1. Aerobic

Bacteria break down glucose with the help of oxygen to produce energy. This energy is channeled into multiplication.

Adequate aeration

Bioreactors- adequate supply of sterile air

These fermenters may have a mechanism for stirring and mixing of the medium and cells

Products: Antibiotics, enzymes, vitamins.

1. Anaerobic

When culture reaches sufficient mass, oxygen is removed. Bacteria switch to anaerobic respiration to produce energy for sustaining of life processes. Alcohol is produced as a result.

Products: Lactic acid, ethanol, wine

Figure 1: Fermenter used in industry

Media used for fermentation

On a large scale one must use sources of cheap nutrient to create a medium which will meet as many as possible of the following criteria:

It will produce a maximum yield of product at biomass per gram of substrate used.

It will produce a maximum concentration of product or biomass.

It will permit the maximum rate of product formation.

It will be the minimum yield of undesired product.

It will be cheap and of a consistent quality and is readily available throughout the year.

It will cause minimal problem in other aspects of production and agitation, extraction, purification and waste treatment.

Composition of the media used for fermentation

All micro-organisms require water, sources of energy, carbon, nitrogen, mineral element and vitamin plus oxygen in their growth medium. On a small scale, it is simple to device a medium containing pure compounds, but the resulting medium although satisfy the growth, may be unsuitable for use in a large scale process.

1. Water

Major component of all fermentation media.

Factors need to be considered

pH

Dissolve salt

Effluent contamination

Nowadays, the water may be treated by deionization or other techniques and salts added, or pH adjusted. In large continuous-culture plants it is common practice to recycle the water streams.It may even be possible to reuse all the water in the fermenter fed with appropriate adjustment of nutrient levels.

2. Energy Sources

Energy for growth comes from either the oxidation of medium components or from light.

Most industrial micro-organisms are chemo-organotrophs, therefore the commonest sources of energy will be the carbon source such as carbohydrates, lipids and proteins.

Some micro-organisms can use methane or methanol as carbon and energy sources.

Carbon requirement for the medium is normally provided by:

Nutrient / Raw material
Sucrose / Sugarcane, sugar beet molasses
Glucose / Corn sugar, starch, cellulose
Lactose / Milk whey
Fats / Vegetable oil
Starch / Maize grains, cereals, potatoes and casava
Hydrocarbons / Petroleum fractions

Barley grains

It may be partially germinated and heat treated to give material known as malt, which contains a variety of sugar besides starch. It is the main substrate for brewing in many countries.Malt extract may also be prepared from malted grain.

Sucrose

Obtained from sugar cane and sugar beet.It is commonly used in fermentation media in very impure form as beet or cane molasses.

Lactose and crude lactose(milk whey)

Now is extremely limited in media formulation since the introduction of continuous-feeding process.Whey is used as a substrate for biomass production

Vegetable oil

Example: olive, maize, cotton seed, linseed, soya bean, etc.

Source of carbon: oleic, linoleic and linolenic acid.it can also be used as anti-foam in association with a surface active agent.

3.Vitamins

Biotin is one of the main vitamins used in fermentation media. It is also known as also known as vitamin H or B7.

TYPES OF FERMENTATION

1. Batch type fermentation
2. Fed batch fermentation
3. Continuous fermentation
4. Solid state fermentation

1.Batch type fermentation

Batch size fermentation is discontinuous process and the fermentor has has to be cleaned after each process and fresh batch started.

It include 5 steps

Fermentor sterilized

Medium added

Innoculum added

Fermentation followed to complete

Culture harvested

Characteristics of a batch fermentation system

•Simplest fermentor operation

•Sterilisation can be performed in the reactor

•All nutrients are added before inoculation

•Maximum levels of C and N are limited by inhibition of cell growth

•Biomass production limited by C/N load and production of toxic waste products

Advantages of batch type fermentation

•Used where end product required in more quantities at a given period of time.

•Useful where the shelf life of the end product is short.

2. Continuous Fermentation

It is a continuous process where the nutrient is continuously added to the fermented at a fixed rate. The organisms are continuously maintained at logarithmic stage. The products are recovered continuously. The fermenters in this type are called “flow through’’ fermentation.

Disadvantages of continuous fermentation

•Complete sterilization is difficult

•More prone to contamination

3. Fedbatch Fermentation:

This fermentation is intermediate of both batch and continuous fermentation. Sterile nutrients are added in increments.

Characters of fed batch fermentation

•Initial medium concentration is relatively low.

•Medium constituents are added continuously or in increments.

•Controlled feed results in higher biomass and product yields.

•Fermentation is still limited by accumulation of toxic end products.

•Finally the products are harvested in one stroke.

4. Solid State Fermentation:

The growth of microorganisms on moist solid substrate particles in the absence or mere absence of visible liquid water between the particles. The moisture content of solid substrate ranges between 12-60%. SSF’s are usually used for the fermentation of agricultural products or foods, such as rice, wheat, barley, corn and soybeans.

Some food fermentations involving SSF:

Wheat by Aspergillus

Soybean by Rhizopus

Soybean by Aspergillus

Characteristics of solid state fermentation:

•The substrate may require preparation or pretreatment like, Chopping or grinding reduce particle size Cooking or chemical hydrolysis Pasteurization or sterilization-reduce contaminants

•Microorganism is usually a filamentous fungus requiring aerobic condition.

•The Inoculum is mixed into substrate to fermentation.

Advantage of SSF:

•A lower chance of contamination due to low moisture levels

•Ease of product separation

•Energy efficiency

Disadvantage of SSF:

•Heterogeneous nature of the media due to poor mixing characteristics.

•At high agitation speeds,mycelial cells may be damage.

•Rotary-tray or rotating-drum fermenters are often used.

Applications of fermentation technology

Antibiotics

Of all the microbial products manufactured commercially, antibiotics are the most important.Antibiotics are chemical substances produced by microorganisms to kill other microorganisms.They are used in the treatment of infectious diseases.

Antibiotics produced by Microorganisms

Antibiotics / Micro-organism
Cephalosporin / Cephalosporium acrimonium
Chloramphenicol / Streptomyces venezuelae
Erythromycin / Streptomyces erythreus
Griseofulvin / Penicillium griseofulvin
Penicillin / Penicillium chrysogenum
Streptomycin / Streptomyces griseus
Tetracycline / Streptomyces aureofaciens
Gentamicin / Micromonospora purpurea

Food products

Milk: yogurt, cheese

Fruits: wine, viniger

Vegertable: pickle, soy sauce

Meat: fermented sausage

Industrial chemicals:

Acetone, Butanol, Ethanol, Enzymes, Aminoacids

Product / Organism / Use
Ethanol / Saccharomyces cerevisiae / Industrial solvents, beverages
Glycerol / Saccharomyces cerevisiae / Production of explosives
Lactic acid / Lactobacillus bulgaricus / Food and pharmaceutical
Acetone and butanol / Clostridium acetobutylicum / Solvents
-amylase / Bacillus subtilis / Starch hydrolysis

Another application of the fermentation process is in the treatment of waste water. In the activated sludge process,aerobicbacteria are used to ferment organic material in wastewater. Solid wastes are converted to carbon dioxide,water, and mineral salt.

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