MCB 412 / 501 BIODETERIORATION / BIODEGRADATION
LECTURE NOTE
Major Microbial Groups Involved in Deterioration/Degradation
Definition
Biodeterioration refers to the undesirable change in properties of materials caused by the
metabolic activity of microorganisms. It includes physical, chemical, and mechanical damage to
natural and synthetic materials. Whereas, Biodegradation is the natural process by which
organic substances are broken down into simpler compounds by the enzymatic activity of living
organisms, primarily microorganisms such as bacteria, fungi, and actinomycetes.
Important Microbial Groups Involved in Biodeterioration and Their Roles
A. Bacteria
General Characteristics:
They are ubiquitous in nature
They demonstrate rapid growth
Possess metabolic diversity
They have the ability to colonize various environments
Roles in Deterioration:
Corrosion: Desulfovibrio (sulfate-reducing bacteria) contributes to metal corrosion by
producing H₂S.
Food spoilage: Pseudomonas spp. degrades proteins and lipids in meat and dairy.
Acid production: Acetobacter produces acetic acid, leading to spoilage of wine and fruit
juices.
Examples:
Pseudomonas fluorescens – causes spoilage of milk and meat.
Bacillus subtilis – causes spoilage of canned foods due to heat-resistant spores.
Clostridium spp. – causes anaerobic degradation in low-oxygen environments, such as
canned foods.
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B. Fungi (Molds and Filamentous Fungi)
General Characteristics:
They are aerobic in nature
Thet thrive in low moisture conditions
They produce spores that are easily dispersed
They can produce mycotoxins (toxic secondary metabolites) that are harmful to health
Roles in Deterioration:
Paper, textiles, and leather: fungi like Aspergillus and Penicillium secrete enzymes that
degrade cellulose and proteins.
Food spoilage: growth of molds on bread, fruits, cheese etc, causes spoilage in foods.
Wood degradation: Fusarium and Trametes produce ligninases and cellulases which
help to degrade woods.
Examples:
Aspergillus niger – causes the degradation of stored grains and textiles.
Penicillium chrysogenum – causes the spoilage of citrus fruits.
Fusarium spp. – causes decay of wood and grains, toxin production.
C. Yeasts
General Characteristics:
They are unicellular fungi that are dimorphic in nature
They are also facultative anaerobes
They are commonly found in sugar-rich environments
Roles in Deterioration:
They play a role in fermentation and spoilage of fruit juices, alcoholic beverages
They are vital in CO₂ and ethanol production leading to off-flavors, bulging of sealed
containers
Examples:
Zygosaccharomyces bailii – This yeast spoils acidic foods (sauces, salad dressings).
Saccharomyces cerevisiae – causes over-fermentation and clouding in beverages.
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Candida spp. – causes spoilage of dairy and meat.
D. Actinomycetes
General Characteristics:
These bacteria are filamentous, Gram-positive in nature
They are found in soil and decaying organic matter
They are slow-growing but produce strong extracellular enzymes
Roles in Deterioration:
Odor production: they produce earthy/musty smell in stored items (e.g., books, wood).
Degradation: they cause the degradation of cellulose in paper, textiles.
Example:
Streptomyces spp. – are able to degrade cellulose, cause discoloration of paper.
E. Algae and Cyanobacteria
General Characteristics:
They are photosynthetic in nature
They thrive in moist, illuminated environments
Roles in Deterioration:
Biofouling: formation of slimy layers on submerged surfaces, pipes, monuments.
Discoloration of building surfaces and stone monuments.
Examples:
Oscillatoria and Chlorella – are common in biofilms that form on damp walls and
fountains.
2. Impacts of Processing and New Technologies on Biodeterioration
A. Traditional Processing Techniques
1. Heat Processing
Effect: The effect of heat processing is that, it destroys vegetative cells; but may not kill
spores.
Examples: Pasteurization of milk (kills Listeria, Salmonella).
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Limitations: Some thermophilic bacteria (e.g., Bacillus stearothermophilus) can survive
this condition.
2. Drying/Dehydration
Effect: Drying/dehydration reduces water activity (Aw), thereby inhibiting microbial
growth.
Impact: It slows down deterioration but xerophilic fungi (Aspergillus, Penicillium) can
still grow.
3. Refrigeration and Freezing
Effect: Refrigeration and Freezing slows down microbial metabolism.
Impact: Psychrotrophs (e.g., Listeria monocytogenes) can still grow at low temps.
B. New Technologies and Their Influence
1. High Pressure Processing (HPP)
This technology uses pressures of 100–600 MPa to kill microbes.
Retains taste, texture, and nutrients.
Inactivates pathogens without heat.
2. Modified Atmosphere Packaging (MAP)
The technology causes alteration of gas composition (e.g., low O₂, high CO₂) inside
packaging materials to prevent microbial growth.
Inhibits aerobic bacteria and molds.
Examples: fresh meats, vegetables.
3. Biopreservation
This involves the use of natural antimicrobials (e.g., nisin, lactic acid) to control spoilage
organisms.
It can help reduce the use of chemical preservatives.
4. Irradiation
This technology destroys DNA of microbes using gamma rays or electron beams, making
them dysfunctional.
It is mostly used for spices, dried fruits and meats.
It is effective against insects, bacteria, and parasites.
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5. Nanotechnology
This involves the incorporation of nanoparticles (e.g., silver, ZnO) into packaging or
surfaces.
The technology act by disrupting microbial membranes, and reduction of biofilm
formation.
It possesses long-acting antimicrobial effect.
6. Smart Packaging
This incorporates sensors that detect spoilage (e.g., pH, gas levels).
It usually may change color to indicate microbial growth.
It helps to improve early detection and food safety.
3. Control of Biodeterioration
A. Physical Control Methods
1. Temperature Control
Cold storage slows down microbial growth.
Freezing inhibits microbial metabolism.
Heat treatment destroys microbes (sterilization, pasteurization).
2. Dehydration
Lowering water activity (Aw) prevents microbial activity.
3. UV and Gamma Radiation
Destroys DNA and inhibits microbial reproduction.
4. Filtration
Physical removal of microbes from liquids (e.g., beverages, pharmaceuticals).
B. Chemical Control Methods
1. Preservatives
Organic acids (e.g., sorbic, benzoic, propionic acids) inhibit fungal and bacterial growth.
Nitrites/nitrates – are used in cured meats to inhibit bacteria such as Clostridium spp.
Sulfur dioxide – is used in wines and dried fruits for preservation.
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2. Disinfectants and Surface Cleaners
Chlorine-based, hydrogen peroxide, quaternary ammonium compounds are used as
disinfectants for achieving asepsis.
They are used in equipment sanitation and water treatment.
C. Biological Control Methods
1. Use of Antagonistic Microorganisms
Lactic acid bacteria produce acids and bacteriocins that inhibit spoilage organisms.
2. Use of Enzymes
These enzymes are able to target specific spoilage organisms or biofilms (e.g., lysozyme,
proteases) for eradication.
3. Phage Therapy
This involves the use of bacteriophages to target and kill specific bacterial contaminants
in products.
D. Preventive Measures
1. Good Manufacturing Practices (GMP)
Ensures clean and hygienic environment to prevent against contamination of poducts
Regular equipment maintenance
2. Packaging Innovations
Vacuum sealing
MAP and smart packaging
3. Material Design
Use of corrosion-resistant or antifungal materials
Proper ventilation and storage conditions
E. Regulatory and Monitoring Measures
Implementation of HACCP (Hazard Analysis and Critical Control Points)
ISO standards, FDA guidelines, and other regulatory frameworks
Microbial load monitoring and quality assurance testing
Conclusion
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Biodeterioration is a multifaceted challenge involving numerous microbial groups.
Advances in processing and preservative technologies have greatly reduced microbial
spoilage.
An integrated approach involving physical, chemical, and biological control methods is
essential to manage biodeterioration effectively in food, pharmaceuticals, textiles, and
industrial materials
