10 - Biodeterioration and biodegradation

Microbial biodeterioration

Microbial-related chemical or physical alterations to a material

Environment dictates whether it will occur and which species will be involved

When can methane be oxidised into CO2

When nitrate levels are high

Reasons for succession

Exhaustion of nutrient sources

Metabolic end products act as substrates

Breakdown in residual host defence

What is Eh

Redox potential

Define water activity

Ratio between water vapour and the water in an item

When does water activity increase

Increase in temperature (%)

Microbial antagonism

One microbial community produces a bacterial that out competes another

Synergism

Where microorganisms support the growth of each other

Commensalism

Relationship between species where one benefits and the other is unaffected

Syntropy / cross-feeding

Where one species lives off of the product of another

Competition

Populations of microorganisms inhabiting a common environment compete for nutrients and resources

Succession

Initial microorganisms change the environment so that other microorganisms can thrive

4 types of biodeterioration

Mechanical

Chemical (assimilatory and dissimilatory)

Fouling

Soiling

Fodders

Crops that are grown for animal foods (eg. hay)

Major groups that undergo biodeterioration

Crops

Wood

Animal products

Metals

Stone

Fuels and lubricants

Problems with fodders

Moulding

Solutions to moulding of fodders

Drying - reduce aw before storage

Preservatives

Ventilation

Biodeterioration of wood

Tends to be stable long term due to low moisture and N content

Fungi is the most prevalent

Biodeterioration of animal products + prevention

Controlled by microorganisms that produce lipases and proteases

Curing, salting, drying

Biodeterioration of paints and coatings

Solvent based - usually stable until applied

What bond provides a point of attack for hydrolytic enzymes

Ester bond (C-O)

Fuel / water interface

Blocked pipes

Water / metal interface

Corrosion

Growth penetration on buildings and structures

Fungi send out hyphae - penetrate deep into various structures and weaken them

Expansion of microbial cells

Communities grow and develop together

Growth into cracks can breakdown the material