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yeast
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Apart from temperature, what other factor could cause yeast cells to denature (be killed)?
Is pH a factor?
Thanks in advance x
Is pH a factor?
Thanks in advance x
Answers
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pH is certainly a factor in Saccharomyces species.
Saccharomyces are acidophilic organisms and the optimum pH for growth lies in the range of between about 4.0 and 5.5. Budding will cease around 2.5. However, it's as well to remember that many factors influence the precise pH for optimum growth including the concentration of oxygen, the precise strain of yeast being studied and the temperature. Yeast enzymes are very intolerant of changes in their environment.
As far as denaturing is concerned, there are a huge number of methods of denaturing yeast cells. In the food industry for example, exposure to pulsed electric fields are very effective. In foodstuffs, substances such as propionic acid and the propionate salts are extremely effective along with Benzoic acid and similar chemicals.
Much work is being done currently on denaturing yeasts using hydrostatic pressure. The problem with this method at the present time is that the equipment needed to perform the task on an industrial scale is very costly.
Much laboratory research centres nowadays on fairly recently discovered complex enzymes that are superb at denaturing many types of yeast cells. Again, adapting in vitro research to an industrial environment is something that needs working on.
There are also drugs such as fluconazole, which show marked activity against the majority of Saccharomyces. The older anti-fungals tend to be tolerated.
UV light can denature yeasts and they are also susceptible to x-rays
Incidentally, I'm curious about they way you've worded the first sentence. If you've quoted it verbatim from somewhere, it's very poorly worded. After all, you could answer that chucking a spoonful of oleum on top of a colony would do the job!
Saccharomyces are acidophilic organisms and the optimum pH for growth lies in the range of between about 4.0 and 5.5. Budding will cease around 2.5. However, it's as well to remember that many factors influence the precise pH for optimum growth including the concentration of oxygen, the precise strain of yeast being studied and the temperature. Yeast enzymes are very intolerant of changes in their environment.
As far as denaturing is concerned, there are a huge number of methods of denaturing yeast cells. In the food industry for example, exposure to pulsed electric fields are very effective. In foodstuffs, substances such as propionic acid and the propionate salts are extremely effective along with Benzoic acid and similar chemicals.
Much work is being done currently on denaturing yeasts using hydrostatic pressure. The problem with this method at the present time is that the equipment needed to perform the task on an industrial scale is very costly.
Much laboratory research centres nowadays on fairly recently discovered complex enzymes that are superb at denaturing many types of yeast cells. Again, adapting in vitro research to an industrial environment is something that needs working on.
There are also drugs such as fluconazole, which show marked activity against the majority of Saccharomyces. The older anti-fungals tend to be tolerated.
UV light can denature yeasts and they are also susceptible to x-rays
Incidentally, I'm curious about they way you've worded the first sentence. If you've quoted it verbatim from somewhere, it's very poorly worded. After all, you could answer that chucking a spoonful of oleum on top of a colony would do the job!
Tut, tut Gef, lighten up.
The laconic sentences strike again, Right, let's see now.
Summersoon asked how yeast cells could be denatured, or put another way (by the questioner, not me), how they could be killed. Regardless of whether we're talking of the physical destruction of the cell by chemical means or otherwise or denaturing the enzymes in the cell, the yeast wiil die. Yes? Isn't that what the questioner asked?
Not much information in "Alcohol does not destroy enzymes but poisons the yeast." is there? Ah, but I forgot you were a chemist and not a biochemist. My mistake.
When I posted my comments I was in a pretty good mood and I thought a lighthearted comment wouldn't be out of place given the rather vague way the question was worded. You've made them yourself on occasions.
Pray, tell us all why you think that yeast would survive immersion in oleum, if that is what you are trying to imply. I think it would be best to explain for those unfamiliar with the term, oleum is more commonly known as fuming sulphuric acid and is extremely corrosive to most substances including living tissue and yeast.
I suppose you are right in one respect though Gef: I'm not currently employed as a chemist. The last time I looked, I was a university biochemistry professor in a Russell Group university with degrees in chemistry, biology and guess what, biochemistry.
(continued)
The laconic sentences strike again, Right, let's see now.
Summersoon asked how yeast cells could be denatured, or put another way (by the questioner, not me), how they could be killed. Regardless of whether we're talking of the physical destruction of the cell by chemical means or otherwise or denaturing the enzymes in the cell, the yeast wiil die. Yes? Isn't that what the questioner asked?
Not much information in "Alcohol does not destroy enzymes but poisons the yeast." is there? Ah, but I forgot you were a chemist and not a biochemist. My mistake.
When I posted my comments I was in a pretty good mood and I thought a lighthearted comment wouldn't be out of place given the rather vague way the question was worded. You've made them yourself on occasions.
Pray, tell us all why you think that yeast would survive immersion in oleum, if that is what you are trying to imply. I think it would be best to explain for those unfamiliar with the term, oleum is more commonly known as fuming sulphuric acid and is extremely corrosive to most substances including living tissue and yeast.
I suppose you are right in one respect though Gef: I'm not currently employed as a chemist. The last time I looked, I was a university biochemistry professor in a Russell Group university with degrees in chemistry, biology and guess what, biochemistry.
(continued)
Regarding the chemistry part, well let's see, I've got a BSc, an MSc, a D.Phil and a DSc in chemistry. Oops, I've just been reminded about my FRSC as well. Perhaps some of these qualifications are the reason why I've been a lecturer and reader in chemistry in my time before I moved into biochemistry.
So go on Gef, tell us all why my lighthearted comment shows that I'm not a chemist. I think I'm not the only one that can't wait.
summersoon, I wasn't having a go at you, honest. The point I was trying to make was that if you had typed the question exactly as it had been written in a question paper, book or notes, the person that had set the question was not being very clear about the sort of answer they were looking for. There are simply too many possible answers - you'll note that my colleague Gef avoided commenting on the ones I gave.
Now that you've explained you worded it yourself, it's pefectly understandable. I was sixteen once myself and I wouldn't have done any better. I'm sure Gef would say the same.
So go on Gef, tell us all why my lighthearted comment shows that I'm not a chemist. I think I'm not the only one that can't wait.
summersoon, I wasn't having a go at you, honest. The point I was trying to make was that if you had typed the question exactly as it had been written in a question paper, book or notes, the person that had set the question was not being very clear about the sort of answer they were looking for. There are simply too many possible answers - you'll note that my colleague Gef avoided commenting on the ones I gave.
Now that you've explained you worded it yourself, it's pefectly understandable. I was sixteen once myself and I wouldn't have done any better. I'm sure Gef would say the same.
prof, I was trying to point out a few facts in as simple a way as possible in order to answer the question.
Your comment about oleum just clouded the issue as the yeast would certainly die but you did not make it clear why.
I presume the last time you looked at your job/qualifications was the last time you stopped looking at the sunshine coming out of your @rse.
I'm afraid I've only got two degrees but at least I know how to explain things to schoolchildren.
Your comment about oleum just clouded the issue as the yeast would certainly die but you did not make it clear why.
I presume the last time you looked at your job/qualifications was the last time you stopped looking at the sunshine coming out of your @rse.
I'm afraid I've only got two degrees but at least I know how to explain things to schoolchildren.
Gef, you've explained your intention in answering the question the way that you did. That's great. However, I'd ask you to consider for a moment if that was the best way. As I said, you were laconic and did not put the answers into context. Don't you think that that would invite a whole host of follow on questions in a classroom environment?
It's many years, since I did my PGCE Gef but one thing I do recall: the need for clarity. Times have changed but perhaps nowadays, teachers give these half-hearted and ambiguous answers in order to keep the lesson going until the bell. It's little wonder we see freshers who seem to have been educated by rote. Right now, it looks like the teachers have adopted the language and format of the multiple-choice paper.
So I clouded the issue by discussing the addition of oleum to yeast, did I? As I told summersoon in the penultimate paragraph of my last post, I did so in order to show that the question worded as it was, was so ambiguous that there were thousands of possible answers. What amazes me is that you, a 1975 graduate, did not appreciate this point. Tell me, how would you have responded if the question were written verbatim in a GCSE chemistry paper? Would you have supported your students and complained to the examination board? Make your mind up which side of the fence you're standing on.
On the same topic, I cannot see why my suggestion of oleum to yeast makes me "not a chemist". Where's the logic Gef? You've chosen not to explain that in your last post but evading explanations does your credibility no good at all. Come on, admit that your accusation was unfair and without foundation in the context of the question.
(continued)
It's many years, since I did my PGCE Gef but one thing I do recall: the need for clarity. Times have changed but perhaps nowadays, teachers give these half-hearted and ambiguous answers in order to keep the lesson going until the bell. It's little wonder we see freshers who seem to have been educated by rote. Right now, it looks like the teachers have adopted the language and format of the multiple-choice paper.
So I clouded the issue by discussing the addition of oleum to yeast, did I? As I told summersoon in the penultimate paragraph of my last post, I did so in order to show that the question worded as it was, was so ambiguous that there were thousands of possible answers. What amazes me is that you, a 1975 graduate, did not appreciate this point. Tell me, how would you have responded if the question were written verbatim in a GCSE chemistry paper? Would you have supported your students and complained to the examination board? Make your mind up which side of the fence you're standing on.
On the same topic, I cannot see why my suggestion of oleum to yeast makes me "not a chemist". Where's the logic Gef? You've chosen not to explain that in your last post but evading explanations does your credibility no good at all. Come on, admit that your accusation was unfair and without foundation in the context of the question.
(continued)
Most of my qualifications were attained through years of hard work Gef. I say most because some of the higher doctorates seem to have jumped on my shoulders while I was asleep. All the same you've spent long enough at uni to know the protocol; it's not the professors' that look at the sun shining out of their @rses so much as the those in academia, politics and publishing who tell them that the sun shines from there. I attended a state secondary modern school and a grammar school (remember them?) and when the need arises believe me, I call a spade a spade.
I'll let you into a secret. I've grown to detest requests to appear on TV over the last few years to explain a scientific matter to the general public. It's time consuming and impinges upon my freedom to walk the streets unnoticed. But once again you see Gef, it's those TV producers that flatter me and stick me on that pedestal not me.
If your 19.29 post on 16/05/07 is typical of your methods of explaining things to children, God help us all. I�ve moved around the country a few times since our first child was born, but all the children have been educated in state schools. The chemistry teachers at these schools have shown an unwarranted eagerness to meet me when they�ve found out who daddy is and I�ve been dragged off to more than my fair share of parents' evenings and soirees � oops, there we go again, another group that holds me in high esteem. However, I�ll tell you for nothing that I�ve never met a chemistry or biology teacher who would contemplate answering a question in the way that you did.
I've been connected with the Royal Institution Christmas Lectures for many years Gef. You'll excuse me if I don't put your name forward as a possible lecturer.
I'll let you into a secret. I've grown to detest requests to appear on TV over the last few years to explain a scientific matter to the general public. It's time consuming and impinges upon my freedom to walk the streets unnoticed. But once again you see Gef, it's those TV producers that flatter me and stick me on that pedestal not me.
If your 19.29 post on 16/05/07 is typical of your methods of explaining things to children, God help us all. I�ve moved around the country a few times since our first child was born, but all the children have been educated in state schools. The chemistry teachers at these schools have shown an unwarranted eagerness to meet me when they�ve found out who daddy is and I�ve been dragged off to more than my fair share of parents' evenings and soirees � oops, there we go again, another group that holds me in high esteem. However, I�ll tell you for nothing that I�ve never met a chemistry or biology teacher who would contemplate answering a question in the way that you did.
I've been connected with the Royal Institution Christmas Lectures for many years Gef. You'll excuse me if I don't put your name forward as a possible lecturer.
Summersoon, thanks for that.
I can't reveal too much here but I can say I've "taught" at quite a few in the UK including two Up North, Cambridge, Oxford and two in central England, not necessarily in that order. Did I mention my current uni? Anyhow, that's most of them in the UK.
I've been a professor and/or visiting professor in Harvard, Stanford, Brown, Cornell and my favourite, the University of Hawaii at Manoa in the USA (the only place I've had a lab set up outdoors in glorious sunshine). I was seconded to certain others over the pond earlier in my career too.
There's also a couple of European universities where I've been asked to do the odd lecture or two.
I can't reveal too much here but I can say I've "taught" at quite a few in the UK including two Up North, Cambridge, Oxford and two in central England, not necessarily in that order. Did I mention my current uni? Anyhow, that's most of them in the UK.
I've been a professor and/or visiting professor in Harvard, Stanford, Brown, Cornell and my favourite, the University of Hawaii at Manoa in the USA (the only place I've had a lab set up outdoors in glorious sunshine). I was seconded to certain others over the pond earlier in my career too.
There's also a couple of European universities where I've been asked to do the odd lecture or two.
prof, I stated some facts and gave a simple answer (not an explanation) to the original question.
Your assumptions about how I (and others) teach are totally unfounded and even you should realise that GCSE questions are more highly structured than that.
summersoon asked an innocent question about yeast not about your life history.
Anyway, I await the next chapter about your qualifications with as much enthusiasm as for a visit to the dentist.
Your assumptions about how I (and others) teach are totally unfounded and even you should realise that GCSE questions are more highly structured than that.
summersoon asked an innocent question about yeast not about your life history.
Anyway, I await the next chapter about your qualifications with as much enthusiasm as for a visit to the dentist.
Gef, I'm curious. Here's a one definition of "answer" from Chambers 21st Century Dictionary:
"to put up a defence to or offer an explanation for something"
I can imagine the scenario. Johnny the teenager asks his chemistry teacher if the alkali metals become gradually more reactive from Lithium to Francium. Teacher says "yes". That's an answer. Teacher chooses not to tell Johnny that this occurs because the atomic radius of each successive element becomes larger causing the sole outer electron of each element to be further and further away from the more distant nucleus. In turn, this means that the outer electron becomes progressively less strongly held by the positive nucleus and is readily lost. That�s a typical explanation.
So it seems that nowadays, you think nothing of giving an answer without an explanation. At least, you admit to having done so with summersoons question. Marvellous, I'm sure your pupils find such methods very enlightening.
But wait, there's more. You say that GCSE are more "highly structured" than I indicated. Now "structured" generally means having a definite predetermined pattern. Ah, now I see it, how stupid of me. It's obvious now. A definite predetermined pattern confines your teaching within boundaries. Therefore, you are unable to expand upon the syllabus and the pupil remains ignorant of the explanation for an answer. Quite fascinating.
(continued)
"to put up a defence to or offer an explanation for something"
I can imagine the scenario. Johnny the teenager asks his chemistry teacher if the alkali metals become gradually more reactive from Lithium to Francium. Teacher says "yes". That's an answer. Teacher chooses not to tell Johnny that this occurs because the atomic radius of each successive element becomes larger causing the sole outer electron of each element to be further and further away from the more distant nucleus. In turn, this means that the outer electron becomes progressively less strongly held by the positive nucleus and is readily lost. That�s a typical explanation.
So it seems that nowadays, you think nothing of giving an answer without an explanation. At least, you admit to having done so with summersoons question. Marvellous, I'm sure your pupils find such methods very enlightening.
But wait, there's more. You say that GCSE are more "highly structured" than I indicated. Now "structured" generally means having a definite predetermined pattern. Ah, now I see it, how stupid of me. It's obvious now. A definite predetermined pattern confines your teaching within boundaries. Therefore, you are unable to expand upon the syllabus and the pupil remains ignorant of the explanation for an answer. Quite fascinating.
(continued)
No doubt that is why you can compose such banal and astonishing sentences like:
"Alcohol does not destroy enzymes but poisons the yeast"
Very helpful that word "poisons", eh? After all, Summersoon admitted to being 16 before you posted that sentence and I'd say deserved a little bit more than the sentence you provided. Is that the sort of answer that's acceptable for GCSE nowadays? And they say accusations of GCSE "dumbing-down" are without foundation.
Pay attention at the back there young Gef. Summersoon asked on Thurs 17/05/07 at 17:25:
"P.S. As a matter of interest, which universities have you lectured at?"
I provided him with short summary of my academic career, which was basically what was asked. My academic career is not my life history Gef as it does not disclose details of my personal life outside academia. They are two separate entities, just as they are in your life.
I know what you mean about my qualifications. You can't appreciate the problems that arise when you've got more than one masters and doctorate in more than one discipline. It's a damn nuisance and I rarely disclose them all.
Funnily enough, I mentioned this to a final year dentistry student the other day when I reluctantly dragged myself off for a free white filling at the Dentistry School (funny perks in this job, I know). I told him he didn't know how lucky he was to be able to graduate and work with a simple BDS after his name.
"Alcohol does not destroy enzymes but poisons the yeast"
Very helpful that word "poisons", eh? After all, Summersoon admitted to being 16 before you posted that sentence and I'd say deserved a little bit more than the sentence you provided. Is that the sort of answer that's acceptable for GCSE nowadays? And they say accusations of GCSE "dumbing-down" are without foundation.
Pay attention at the back there young Gef. Summersoon asked on Thurs 17/05/07 at 17:25:
"P.S. As a matter of interest, which universities have you lectured at?"
I provided him with short summary of my academic career, which was basically what was asked. My academic career is not my life history Gef as it does not disclose details of my personal life outside academia. They are two separate entities, just as they are in your life.
I know what you mean about my qualifications. You can't appreciate the problems that arise when you've got more than one masters and doctorate in more than one discipline. It's a damn nuisance and I rarely disclose them all.
Funnily enough, I mentioned this to a final year dentistry student the other day when I reluctantly dragged myself off for a free white filling at the Dentistry School (funny perks in this job, I know). I told him he didn't know how lucky he was to be able to graduate and work with a simple BDS after his name.
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