From WikiEducator
Jump to: navigation, search

This is based on New Zealand Qualification Authority Unit 8027 [1] entitled "Discuss microbial biodeterioration and biodegradation."

1.1 and 1.2

Biofilms are the communities of micro organisms and have a self developed polymeric matrix and adherent to an inert or living surface. They can also form on interfaces, i.e in oil and water or air and water. It is usually formed with the attachment of the free floating microorganisms to a surface. Pseudomonas aeruginosa produces exopolysaccharide which makes it slimy. When bacteria join a biofilm, they often express genes that have been previously repressed. Therefore, they often look different to the free living versions of themselves. [2]

Microbes usually prefer living in the biofilms because the microbes uses the metabolic by-products or wastes produced by the slime layer of biofilm as their food. Microbes are even able to last long within a low-nutritive environment of a biofilm. Protein/enzyme combined with polysaccharide complexes help with the organisation and cooperation to occur within the biofilm. Within the structure of the biofilm, the microbes can achieve a basic homostasis by the circulation of fluids, exchanging metabolites and maintaining levels of pH, oxygen and carbon dioxide.[3]

Biofilms are a population of bacteria, algae, yeast or fungi that grow attached to a substance, it can be living or non living. Living things found in teeth, gums, cells of intestinal or vaginal tract, and non living things found in medical devices such catheters. Microbial mats can be considered as complex biofilms. [4]

This website outlines why biofilms occur and why microorganisms live in them Biofilms

Advantages of Biofilms:[5]

Bacteria when organised in biofilms can produce effective substances which cannot be produced by an individual bacteria.

1. Avalibilty of nutrients for growth 2. Increasing the binding of water molecule 3. Protection from uv radiation 4. Produce consoritia which allows the recycling of substance 5. Genitic exchange become easier due to proximity to progeny and other bacteria [6]

Bacteria (Acetobacter xylinum) present on the surface of fruit and flowers play an important role in commercial production of wines and other fermented substances .Biofilms found on the solid supports in sewage-treatment plants play major in processing of sewage water before it is discharged into rivers.[7]


Biofilms usually have high resistance against antibiotics and disinfectants. Thus it is little difficult to completely control them.

There are many reasons for microorganism having biofilms some of the advantages and disadvantages are outlined at "Bakers' yeast Blooms into Biofilms

This review provides a basic understanding of what biofilms are, the problems they can cause, and what might be done to deal with them.


Biofilms produce clinical symptom like prosthetic hip joint,it contribute the pathogenesis of keratitis because of its rapid production in contact lens,organisms within a biofilm are difficult to destroy by common antimicrobial therapy. [10]

[Power Point presentation - Describe Biofilms][11]

2.1 and 2.2

Biodegradation is the process that occurs when organic materials are broken down by enzymes that are produced by microorganisms.[12]

These websites give more examples of biodegradation of natural materials:
Biodegradation of Natural Oils in Seawater
Biodegradation of Natural Rubber and Related Compounds

This piece of research studies how fungi affect leaf decomposition:

Biodegradation is the process of breaking down an organic substance by enzymes produced by living organisms. A banana can take 2-10 days, orange peels take one month, paper take 2-5 months, sugar cane pulp products 1-2 months.[13]

This is some current research into useful biodegradation on contaminated water:

Xenobiotics are synthetic organic compounds and they generally have chemical properties that cannot be broken down by microbial degradative enzymes. This is because the xenobiotics have been developed recently, from a geological viewpoint, and the existing microorganisms haven't encountered them and therefore are not prepared to biodegrade them.[14]

Ex) Plastics have high chemical resistances due to their excessive molecular size for biodegradation. Pyrolysis enables plastics to be degraded through reducing their molecular size to short biodegradable fragments.[15]

Lignin is the material found in woody plants and it makes 20-30% of wood. It is found in the cell wall and appears as a complex with cellulose and hemicellulose polysaccharides. White rot fungi has a heterogeneous collection of basidiomycetes which completely mineralize both lignin and carbohydrate compound of wood by an oxidative cleavage of the propanoid side chain and also by demethylation and oxidation cleavage of aromatic rings.[16]

Websites with more examples of biodegradation of xenobiotics:
Biodegradation of xenobiotic compounds
Biological Degradation of 2,4,6-Trinitrotoluene

[Power Point presentation - Describe Biodegradation][17]

3.1 and 3.2

Biodeterioration is an undesirable change in the properties of materials caused by vital activities of organisms.[18]

Biodeterioration is the process that produces undesirable change in the properties of materials by the activity of organisms. It is classified into two categories. In assimilatory biodeterioration, the organism uses material as a food or energy source. In dissimilarity biodeterioration, change occurs in materials due to the excretion of waste products, such as pigmented or acidic compounds produced by the microorganisms.[]

Biodeterioration of meterials

1. paper: Paper pulp can be produced chemically or mechanically. Chemical paper pulp produces less nutrients for microorganisms than the mechanical one. Bacteria and fungus cause deterioration in paper resulting in poor quality of sheets.
2. wood: Wood decay is mainly caused by fungus. Suitable environmental conditions like temperature, moisture and oxygen are necessary for wood decay.
3. textiles: When fiber is continuously exposed to temperature and moisture it changes. Certain organisms produce pigment or growth of cellular fibers. This causes colour and weakness in the fiber and subsequently poor quality of materials result.
4. paint and painted surface: Both micro and macro organisms attack painted surfaces. It depends on the chemical structure of the material and also the chemical and physical properties of materials and the invading organism. [19][20][21]

5.Rubber: The deterioration of rubber by various fungi and actinomycetes might cause serious electrical problems to buried cables. Biodegradation of rubber is a slow process, bacteria utilizing rubber as a sole carbon source is also slow. Incubation periods can take weeks or months for obtaining degradation products for further analysis[22]

6.Metal: The corrosion of metal pipes due to some bacteria triggers serious problems, particularly in oil and gas delivery systems. Metals used in marine environments or the walls of the fuel tanks of jet aircraft are susceptible to microbial corrosion. Pitting and scaling of the metal occurs beneath heavy, slimy growths of hydrocarbon utilizing bacteria such as species of Pseudomonas and Desulfovibrio.[23]

Examples of bioterioration: [24]

Biodeterioration [25] also has a impact on a wide range of materials including Stone and Woodevaluation of biodeterioration is very important especially in situations such as construction.

Preventive methods: Physical methods like drying(freeze drying) or cooling and chemical methods such as adding biocide or preservative are effective methods used to prevent biodeterioration. Use of low cost materials is the another preventive method. Gamma irradiation is a good preventive method for wood decay. []

These websites out line the prevention methods[26] used for Stone and Wood

This website is a study conducted from samples of the Milan Cathedral. This historic site has suffered corrosion, despite treatment with synthetic polymers.

[Power Point presentation - Describe Biodeterioration][27]


Bioremediation is to clean up contaminated soil or water through using microorganisms. For example, the oil industry uses bacteria to clean up pollution created by spills and underground leaks and to clean up waste products from oil production.[28]

This website describes what bioremediation(James J. Valdes, 2000) is and the different types of Bioremediation[29].
Bioremediation of chlorinated solvent contaminated groundwater.

James J. Valdes. 2000. Bioremediation. Springer.

Bioremediation refers to any process that use microorganisms, green plants or their enzymes do to return the natural environment, which was changed by contaminants, back to its original state. It is used against specific contaminants. Bioventing, bioreactor, composting, bioaugmentation, rhizofiltration and boistimulation are the major bioremediation techniques[30]

Bioremediation example:

Bioventing is a process which provides oxygen by stimulating naturally occurring soil microorganisms to degrade components in soil. It is useful in remediation of the soil contaminated with non chlorinated solvents, some pesticides, wood preservatives and organic chemicals. [31]

Composting involves breaking down of organic materials by a large number of bacteria and fungi. These require oxygen and moisture to break down organic material[32]

Bioaugmentation is addition of a group of natural microbial strains or a genetically engineered variant to treat contaminated soil or water.[33]

Anaerobic Digesters: These are huge tanks which sludge is pumped into from the settling tanks. Here volatile material is reduced and the colloidal water-binding structure is destroyed. Within these tanks, anaerobic bacteria are metabolising the sludge and helping to break it down into alcohols, acids and gases. Because a lot of gas is produced, the tanks have floating lids on top so that the volume can fluctuate without letting air in. A mixture of air and gas could cause an explosion and oxygen is poisonous to the bacteria.
The objectives of anaerobic digestion are
1. Decompose the sludge organics
2. Produce useful by-products
3. Reduce the mass and volume of sludge and
4. Destroy or control pathogens.
The sludge acts as a carbon source to the bacteria. The bacteria are facultative anaerobic acid producers. They use the carbohydrates, proteins and fats which they convert to organics and alcohols (mostly acetic and propionic acids). Then the anaerobic methane fermentors convert the acids and alcohols to methane and carbon dioxide. The methane produced can be used as fuel and is extracted from the top of the tank. The Palmerston North City Council Sewage Treatment Plant uses their methane to operate the central heating system and for maintaining the temperature in the digesters. They are now also selling the methane to the nearby businesses. Another product that can be made is from the digested solids. It is full of nutrients and can be made into a supplement for livestock.
The tanks operate at 35-60°C and hold the sludge for 15-25 days. The Palmerston North City Council (New Zealand) Sewage Treatment Plant holds their sludge for about 20 days at 35°C.
Inside the tank, mixing is constantly moving the sludge around. This improves the anaerobic process in five ways.
1. It distributes the incoming sludge and keeps the organisms active by keeping a continuous supply available to them.
2. Distribute the alkalinity buffer throughout the tank and helps keep the pH under control.
3. It maintains the same temperature throughout the tank.
4. Minimises the concentration of growth inhibitory materials.
5. Minimises and prevents scum build up.

[Power Point presentation - Describe Bioremediation][34]