Fermentation
The controlled action of selected microorganismsFor:–
– Treat waste
– Production of new products
– Helps preserve foods
– Alter texture of foods
Main advantages
• Generally simple technology
• High efficiency
• Environmental friendly
Microorganisms used in fermentation
•Bacteria•Molds
•Yeasts
Bacteria
•Acetobacter•Pediococcus
•Lactobacillus
•Leuconostoc
•Streptococcus
Molds
•Aspergillus•Mucor
•Penicillium
Yeasts
•Saccharomyces•Kluyveromyces
Factors that control the growth of MO in food fermentation
Intrinsic factors
•Parameters that are an inherent part of the medium and can alter MO growthExtrinsic factors
•Properties of the storage environment that affect the growth of MOIntrinsic factors
•Nutrient content•Substrate pH
•Antimicrobials
•Redox Potential
•Water activity
Extrinsic factors
•RH of environment
•Atmosphere
•Presence of other MO
Bioreactors
• A bioreactor is a reactor system used for the culture of microorganisms.•They vary in size and complexity from a 10 ml volume in a test tube to computer controlled fermenters with liquid volumes greater than 100 m3.
Types of Bioreactors
Some examples for bioreactors
•Standing cultures
•Shake flasks
•Stirred tank reactors
•Bubble column and airlift reactors
•Fluidized bed reactors
•Standing cultures
•Large Pyrex flasks are used for the small scale production of fermented products.•Standing cultures - Surface cultures
•The Aspergillus niger mycelia are grown on the surface of liquid media in large shallow trays.•The solids may be continuously or periodically turned over to improve aeration and to regulate the culture temperature. One example of a commercial scale, solid substrate fermentation is the production of koji by Aspergillus oryzae on soya beans which is part of the soya sauce process.
Shake flasks
•Shake flasks are commonly used for small scale cell cultivation. Through continuous shaking of the culture fluid, higher oxygen transfer rates can be achieved as compared to standing cultures. Shaking continually breaks the liquid surface and thus provides a greater surface area for oxygen transfer. Increased rates of oxygen transfer are also achieved by entrainment of oxygen bubbles at the surface of the liquid.
