Factors Affecting Microbal Growth Flashcards
Name 4 factors that affect microbial growth?
-temperature
-pH
-moisture content
-aeration
What are some pH effects on microorganisms?
- extra cellular enzymes
-ph optima
What is the optimum pH for most micro-organisms?
7.0 they are neutrophilic
At what pH is bacterial growth inhibited or low at?
5.0 & below
What pH does bacteria grow best at?
pH3/4
What as a group are more acid tolerant than bacteria?
Fungi
In what conditions do fungi grow in?
Optimally at pH 5.0
Few grow well at pH values as low as 2.0
What are examples of microbial diversity?
• anaerobes
• aerobes
•microaerophiles
Why is carbon dioxide (CO2) an important factor in the atmosphere?
- pH changes
- may be inhibitory at high concentration
What causes the growth rates of micro-organisms to increase?
Increasing water content of substrates
What does water availability depend on in the environment?
•absolute water content of the environment
•salt concentration
What is water availability also expressed as?
Water activity
Define water activity
The relationship between the moisture content of the substrate and the relative humidity of the air surrounding it
What value does water volume have?
1
(Most foods and microbial culture have values less than 1)
Name 4 environmental stress conditions;
1 temperature
2 pH
3 lack of nutrients
4 presence of toxic substances
