F.biotech L1&2 Flashcards
Fungal biotech includes the use of?
Yeast, filamentous fungi in applied bioscience and technology
What year was the role of yeast in brewing discovered?
1863
Use of fungal enzymes in the food industry:
Sweets, juices, cheeses are processed using fungal enzymes
Fermentation can be used to produce:
-Primary metabolites eg acetic acid
- secondary metabolites eg antibiotics
- enzymes, lipases
Fungi is used in fermentation because?
They are easy to manipulate and grow relatively quickly. They are cheap and most aren’t pathogenic
Choice of fermentation system depends on?
Cell type eg the mean generation time (mgt) for bacteria is 0.25- 1hr
Mgt for yeast is 1.15-2hrs
Types of fermentation systems used by fungi
-Solid fermentation
-Film fermentation
-Batch fermentation
-Fed batch fermentation
-Cell recycle batch fermentation
- Continous fermentation
Solid fermentation
This is the oldest system. Fungus grows on solid substrate to produce biomass or to secrete material onto the substrate eg sot sauce. Some water is required.
Example of solid fermentation
Mushroom production(Agaricus bisporus). Inoculate compost wuth mushroom spores, they can then germinate and grow. The compost can then be converted into biomass. There is no free water present hence fungus must be able to tolerate dry environment
Symba process
Use of fungal species or a mixture of species to concert waste eg straw to fungal biomass.
Example of fungal
Species that work in the symba process
- Candida lipolytica
- Chaetomium cellulolyticum
They breakdown straw to make biomass that can be fed to animals
Biomass
Animal feed
Examples of solid substrate fermentations
- Production of mushrooms, from breakdown of straw/manure using a.bisporus
- Production of soy sauce from breakdown of soy beans using aspergillus oryzae
- Production of cheese from breakdown of milk curd using penicillum Sp.
Film fermentation
Fermentation occurs in layer/ film to produce antibiotics. As the fungus grows, it secretes antibiotics to the medium below it.
Film fermentation
Fermentation occurs in layer/ film to produce antibiotics. As fungus grows, it secretes antibiotics to the medium below it.
Batch fermentation
Growing cells in a medium, giving them optimum conditions and harvesting the product when they are finished growing
What happens in the lag phase of the growth curve?
Cells are adapting to the environment including nutrients, ph and temperature.
There is intense biochemical activity and synthesis of enzymes
What happens in the acceleration phase of the growth curve
Growth is transient
What happens in the exponential phase?
There is unlimited growth
No inhibitors
High nutrients
Initially low cell number
What happens in the deceleration phase
Growth slows down
Nutrient levels drop
Increased levels of inhibitors
Alterations in ph
Toxin levels grow
What happens in the stationary phase
No overall increase in numbers
Nutrient depletion
High level of inhibitors
Rate of growth= rate of death of cells
What happens in the death phase
Cell lysis
Spore formation
Viable but non culturable (VBNC) state
Nutrient levels in stationary phase
Nutrients are consumed
There is low rate of depletion
Logarithmic depletion
Rate of use slows
Disadvantage of batch fermentation
Biphasic growth: end product may be metabolized in absence of other nutrients ie as the product is being produced, they can begin to consume it eg yeast produces ethanol but can also consume it
Fed batch fermentation
This is the most used type. Nutrients are added on a continual basis to the fermentation. Medium/ substrate is also added while nutrients are added to produce biomass eg production of bakers yeast
Advantage of fed batch fermentation
Good for growing biomass as they have lots of nutrients, oxygen
Disadvantage of fed batch fermentation
It doesn’t favor fermentation, not good for producing ethanol. As the system has as much nutrients as possible ie a large amount of oxygen, aerobic growth is favored than anaerobic growth. Lack of oxygen causes cells to ferment.
Cell recycle batch fermentation (Melle- boinot process)
Cells at the end of one batch are reused as starter for fresh fermentation.
How does reusing cells affect energy of fermentation
It reduces the amount of energy needed as cells have nutrients already and are ready to ferment. Cells then have more energy to make more end products.
Advantage of cell recycle batch fermentation
Good for growing ethanol. Production of wines, beer
Disadvantage of cell recycle batch fermentation
It may be strain/ species/ substrate specific ie it doesn’t work for all cells
Continuous fermentation
Cells grown under steady state conditions (SCP). Variables are in a constant environment. It goes on for long periods of time
What phase of the cell cycle is continuous fermentation held?
The stationary phase. It holds cells here for long periods of time by taking medium in and out at a constant rate.
Advantage of continuous fermentation
Good for growing antibiotics
Disadvantage of continuous fermentation
It is expensive to set up and difficult to stop it from getting contaminated
Factors affecting fermentation productivity
- Type of fermentation system
- Nature of fungus
- Medium
- Temperature
- PH
- Aeration
- Agitation
- Moisture content
Nature of fungus: cell form
Some fungi are:
-single cell eg yeast (s. Cervicea). They are easy to grow, demanding environment
- mycelia’s form eg penicillum. They are delicate, have hyphae/ filaments that can break, cells die
Nature of fungus (oxygen)
Some fungi are:
- Aerobic: good for growing biomass
- Semi-aerobic: good for growing ethanol
- Anaerobic: good for growing antibiotics
Nature of fungus (requirements)
Some fungi have special requirements:
Inoculum. Some have quorom sending; low density of cells may affect fungal growth
Nature of fungus
Some fungi have END PRODUCT TOLERANCE
End product tolerance
The ability to produce ethanol is limited by the sensitivity of ethanol. We want to vary sensitivity of cells and increase their tolerance by membrane loading. For example, adding ergosterol into growth medium, fungi metabolizes it making the cell wall more rigid, reducing the chance of ethanol destroying the cell membrane. Like this, ethanol does not have the same damaging impact and cells can tolerate higher levels of ethanol. Same can be said for antibiotics.
Medium
Optimizing the medium by increasing carbon & nitrogen in metabolizable form will maximize yield
Temperature regulation
Optimum temperature is good for optimum activity of enzymes
What is the temperature range for fungal fermentation?
20-37 degrees
Beer: 20 degrees
Antibiotics: 30 degrees
How does aeration influence productivity of a fermentation
For biomass: lots of oxygen needed
For ethanol production: no oxygen required
How does agitation influence productivity of a fermentation?
It can be damaging as it can break mycelial forms of fungi
What are the two most used fermentation systems?
Batch and fed-batch systems
What is batch fermentation mainly used for?
Alcoholic products
What is fed-batch fermentation mainly used for
Bread production
Advantages of batch and fed-batch systems
- product often stored in stationary phase
- easy to set up; not as difficult as continuous
- batch size variable
- prevents loss of strain specific characteristics eg aroma, cells
- most fermentations were historically batch
