6.2.1 - (f-g) Flashcards
What are the advantages of using microorganisms to make food for human consumption?
- Microorganisms reproduce fast so food production can be increased to match demand
- Microorganisms have high protein content and little fat content
- No animals are used so it is vegetarian
- No welfare issues
- Microorganisms can be genetically modified to produce required proteins
What are the disadvantages of using microorganisms to make food for human consumption?
- Some microorganisms produce toxins in the wrong conditions
- The microorganisms must be separated from the nutrients and must be processed to make food
- Need sterile conditions increasing cost
- People dislike the though of eating food grown by fungi (single cell), as it is seen as unclean
- Needs flavour as it has little additives
- Protein produced by fungi won’t taste the same as actual meats
What are aspetic techniques and why are they important when culturing microorganisms?
- In a lab, microorganisms are cultured in either a liquid broth or an agar plate
- Nutrients are added to each medium to produce better microbial growth
To culture microorganisms, aseptic techniques are important
Aseptic techniques: Techniques used to culture microorganisms in sterile conditions so they are not contaminated with unwanted microorganisms
What are general aseptic techniques?
- In general, hands should be thoroughly washed
- Working area should be disinfected with a disinfectant or alcohol
- Sterilisation – ensure all equipment is sterile and free from contamination by using an autoclave. Heats water under pressure to 120oC
- Inoculation - introducing microorganisms to mediums where they can grow
Describe the process of innoculating broth
- Make a suspension of the bacteria to be grown
- Mix a known volume with the sterile nutrient broth in the flask
- Stopper the flask with cotton wool to prevent air contamination
- Incubate at a suitable temperature
Describe the process of innoculating agar
- Light a Bunsen burner, this sterilises implements but heats the air so airborne microorganisms do not settle
- Inoculate the wire loop by heating in the Bunsen flame until glow red
- Whilst it cools, it cannot touch any surfaces to avoid contamination
- As the bacterial culture bottle neck is opened, pass through the flame to prevent bacteria contaminating, dip the loop in
- Lift the Petri dish and draw a zigzag with the wire loop
- Replace the lid but do not fully seal, to allow oxygen in
- Incubate at a suitable temperature
What are primary and secondary metabolites?
Primary metabolites: They are produced during the normal metabolism of a microorganism
Secondary metabolites: Produced after the main population growth has occurred. They are not essential substances, but are still used
An example of a secondary metabolite is the antibiotic Penicillin
What are the two main ways of industrially growing microorganisms?
The two main ways of industrially growing microorganisms are batch fermentation** and **continuous fermentation in a fermenter
Fermenter: A large vessel with the correct conditions for microorganism growth
What are the characteristics of batch fermentation?
- Microorganisms are inoculated at into a fixed volume of medium
- The nutrients are added at the start only
- As growth continues, nutrients are used up and new products are created
- Once the culture reaches a stationary phase, the growth ceases but secondary metabolites begin to form
- The process is stopped before the death phase and products collected
The growth rate is slow as nutrients are added at the start only and in the event of contamination only one batch is lost
What are the characteristics of continuous fermentation?
- Microorganisms are inoculated into a sterile medium and grow
- Nutrients are continually added in the exponential phase and the products (culture broth) is continually collected to keep the culture volume in the bioreactor consistent
There is a fast growth rate due to continual nutrient addition. It is useful for producing primary metabolites
Why is it important to manipulate growing conditions and what should be monitored in a fermenter?
A fermenter can be used to optimise growing conditions to maximise yield
- Temperature - Must be warm enough to ensure a high enough metabolic yield but not too high that the microbials denature
- Nutrients - Oxygen and nutrient mediums are added in controlled amounts when probes indicate the nutrient levels are dropping
- pH – must be maintained to ensure enzyme action continues
- Mixing – bioreactors must keep the substances mixing as simple diffusion is not enough to supply all microorganisms with nutrients
- Asepsis – if a bioprocess is contaminated, the yield is affected
