yeast fermentation - (May/22/2011 )

within how many hours does yeast end its exponential growth and enter the stationary phase ?
after 24 hours, its growth is still increasing, is it possible or not ? if it is , why could it happen? as i know, yeast growth stop withink 24 hours, is it right?
in defined medium added amino acid with sucrose and glucose, its growth rate is better in glucose than in sucrose, but in without amino acid defined medium, sucrose is better and after 24 hours, it already in log phase,but yeast are still growing in glucose defined media without amino acid after 24 hours. i think it is because of its speed of growth and availablity of energy source. how about you ? what would you think on that ?

if you know explaination for any of these questions, please share.

Thank you.

Is this a homework question?

yes.. do you know explaination to this ? because i am confused.

gebirgsziege on Mon May 23 06:43:33 2011 said:

Because we do not answer homework questions here, we look at them and help you to answer them, but do not make your homework.

I suppose you are talking about Saccharomyces cerevisiae when you are talking about yests?

You should try to think about - the structure of sucrose and glucose

for the exponential phase you should think about nutrient availability vs. cell number

I do not really get your point here, maybe you can explain this in more detail?

And: it is not a general truth that yeast growth stops after 24h - the time how long a culture is growing (also exmonentially) depends on various factors (e.g. temperature, pH, O2, nutrients...).

gebirgsziege on Mon May 23 11:56:51 2011 said:

n defined medium added amino acid with sucrose and glucose, its growth rate is better in glucose than in sucrose, but in without amino acid defined medium, sucrose is better and after 24 hours, it already in stationary phase,but yeast are still growing in glucose defined media without amino acid after 24 hours.

yeast growth in defined medium with sucrose were in stationary phase, not LOG .. sorry for confusion. But, yeast in defined medium with glucose are still on exponential stage. that is what I am thinking why the diference in growth phase after 24 hours.

thank you very much for your answers.

best wishes xx