effect of temperature on the survival of yeast cells

[smudgy]

In this investigation I will be using baker’s yeast similar to brewer’s yeast. I need to plan an investigation to find the lowest temperature that kills all the yeast cells in a suspension to either dried or fresh baker’s yeast.

My planning must be based on the assumptions that I am provided with the following:

• 10% suspension of yeast
• 10% solutions of sucrose or glucose
• 1.0% methylene blue solution
• School or college laboratory resources.

I need to give full details of my plan which needs to include:

• Apparatus and materials to be used
• Detailed method to include procedures that I would adopt to ensure that the results obtained were as precise and reliable as possible
• A risk assessment and safety precautions.

I need to indicate briefly how I would present and analyse my data to draw conclusions.

[sudad_tariq]

Is that an MSc or PHD project??

[thehundredthone]

@sudad_tariq: Why would you think that?

@smudgy: A simple table with the temperature in one column and whether or not the cells survived in the other should do, right? I would think you would use histograms or other graphical methods to present your data, only if you're going to count cells/size of culture.

How precise do you have to be in your temperature finding? Decimals?

[flyingbarbie]

In this investigation I will be using baker’s yeast similar to brewer’s yeast. I need to plan an investigation to find the lowest temperature that kills all the yeast cells in a suspension to either dried or fresh baker’s yeast.

My planning must be based on the assumptions that I am provided with the following:

• 10% suspension of yeast
• 10% solutions of sucrose or glucose
• 1.0% methylene blue solution
• School or college laboratory resources.

I need to give full details of my plan which needs to include:

• Apparatus and materials to be used
• Detailed method to include procedures that I would adopt to ensure that the results obtained were as precise and reliable as possible
• A risk assessment and safety precautions.

I need to indicate briefly how I would present and analyse my data to draw conclusions.

could you please tell me how u carried out this experiment as i have a similar one to do and don't know where to begin my write up

this would be really helpful

thanks

[mith]

Just do it like a binary search, pick a high temp, then a low temp, then pick a point in between and iterate.

[psycho_scorpyen]

yeah i'm doing the same thing, i figured ten test tubes each in a water bath with 10 degree intervals should give you a rough idea, then once you have the test tube with the highest temperature that's still colourless (the methylene blue indicator) you can heat it up one degree at a time and find the exact temperature that kills the yeast cells.

anyone see any holes in this? i'm stuck too, no idea how to display my results.

[flyingbarbie]

i don't actually have to carry out the experiment but i only have to write the theory behind it...though i did a preliminary experiment which didn't give clear results. the methylene blue was too concentrated at 1%

[Doive]

Yes, I am doing this write-up too.
I guess it's not too complicated really, the yeast will denature at around 40-65 celsius, which means the colour from the indicator won't change. Do preliminary work to work out a rough approximation and take it from there. I'd suggest using a colourimeter if you can, to measure the colour density of the blue colour.
@psycho_scorpyen: I'd say 10 test tubes is too many, try to cut it down to around 6, apart from that your idea sounds good. As for showing the results...

A colourimeter has got to be the best idea, measure the intensity of the light getting through the blue colour. Find the maximum light intensity (it will be when all the yeast is dead) and the temperature at that point is your answer.

Any suggestions to improve this plan will be appreciated

[CoffeaRobusta]

Wouldn't the [b]lowest[b] temperature to kill all yeast be absolute zero? Hahahahaha. Seriously, I would probably plot this as an x-y graph.

[alcyon]

@sudad_tariq: ....I think i did that in yr10...

[Doive]

Wouldn't the [b]lowest[b] temperature to kill all yeast be absolute zero? Hahahahaha. Seriously, I would probably plot this as an x-y graph.

Absolute zero wouldn't kill/denature them, it would just mean they would work incredibly slowly (or not at all). Too high temperatures kill the yeast, not too low

[wassup]

im doing this at the moment too.

for your plan how long did you say you were going to leave the methylene with the yeast?

please help