LAB - industrial application and bacteriophages Flashcards
What are the two techniques of LAB preparation? and what are the disadvantages?
- Practice of starter propagation -> prone to bacteriophage infection and hygiene
- Direct Vat inoculation -> can be expensive as u always need to buy from supplier for each fermentation process.
Why does lactic acid not reduce pH as well as HCl?
Because lactic acid is a weak acid and thus is in balance with its unprotonated form and has a pka of 3.9. Approaching this pH will lead to the pH reduction to slow down.
Why do different lactic acid reduce differently pH?
Because it depends on the soluble matter of the product. Proteins and other substances can act as buffer and thus slow down pH reduction.
What are bacteriophages?
Bacteriophages are bacteria eaters
How is the reproduction of the bacteriophage called and describe the process?
It is called the lytic cycle and involve the following steps
1. Recognition
2. Adsorption
3. DNA Injection
4. DNA replication
5. Synthesis of new phage
6. Many new phages
7. Cell lysis and phage release
Which methods to bacteria employ to defend themselves from bacteriophages?
- Mutate the receptor
- Break down the DNA injected
- CRISPRS-Cas cuts DNA sequence
- Suicidal of infected cell so that phage cannot propagate into other bacteria
however phages have also adapted to counteract this measures so there is no real winner.
How is the first phase of phage growth called? And the second phase?
Latent period- just after infection and until new phages are produced. The phage number is constant.
The second phase is known as burst size.
What are the 3 consequence of bacteriophage attack?
- Slow acidification
- Increase risk of spoilage and growth of pathogen
- Loss of complete batches
Are mixed or single strain more resistant to bacteriophage? Will both be able to grow?
Mixed. Both will die a bit, single strain more, but increase afterwards as even low amount of resistant strain if can survive they can replicate. It will just take longer.
Does pasteurization kill phages?
No, not fully.
What is the other life cycle that bacteriophages can decide when attacking a bacteria?
The lysogenic cycle. It involves the DNA injected by the phage to be incorporated into the DNA of the bacteria. If then the bacteria is damaged, the phage DNA will detach as senses that the environment is not safe any more and enter the lytic cycle. This type of cycle is more dangerous as the bacteria population cannot recover from it. However, if phage sequence get damaged or mutated then when entering the lytic cycle the phages may not be able to carry out their role any more.
What are the positive effect of phages to bacteria?
Bacteria builds superinfection immunity which send signals to other phages communicating that the bacteria is already infected.
What are some strategies to control or reduce contamination of bacteriophage?
- Sanitation and good process design
- Culture rotations to avoid build up resistance from phages
- Understanding which phages are present and selecting appropriate starter cultures.
