Search found 11 matches

by ilovebiology77
Mon Mar 12, 2012 12:26 am
Forum: Microbiology
Topic: How to buffer?
Replies: 1
Views: 1267

How to buffer?

Hi there, so I want to buffer a yoghurt product to pH 5... in order to do this, would I simply add an amount of pH 5 buffer solution to the yoghurt pot... how much would I need to add approximately to a 100ml yoghurt pot if this is correct?

Many thanks :)
by ilovebiology77
Wed Feb 29, 2012 4:33 pm
Forum: Microbiology
Topic: Are there any pH indicators which can kill bacteria?
Replies: 2
Views: 2289

Thanks a lot JorgeLobo, will google it and read up about it now. :)
by ilovebiology77
Wed Feb 29, 2012 4:11 pm
Forum: Microbiology
Topic: Why is my negative control showing results?
Replies: 3
Views: 1965

Why is my negative control showing results?

Hi there, so I used MRS agar to grow lactic acid bacteria. As a negative control, I used a neutral pH, 7 as suggested by members on this forum. I expected no growth of lactic acid bacteria. However, I observed there was still quite a considerable amount of growth. I'm rather confused as this is well...
by ilovebiology77
Tue Feb 28, 2012 7:57 pm
Forum: Microbiology
Topic: What is the positive control and negative control?
Replies: 9
Views: 9094

Ahhh I see, you're controls make sense now!

Thanks to both of you, you helped a lot ! :D
by ilovebiology77
Tue Feb 28, 2012 7:56 pm
Forum: Microbiology
Topic: Are there any pH indicators which can kill bacteria?
Replies: 2
Views: 2289

Are there any pH indicators which can kill bacteria?

I'm thinking of using bromocresol purple to identify lactic acid bacteria colonies but was wondering whether there are any I should definitely avoid as it could kill or inhibit the bacteria in any way?

Thank you :)
by ilovebiology77
Mon Feb 27, 2012 10:43 pm
Forum: Microbiology
Topic: Question on oxidative phosphorylation?
Replies: 0
Views: 1372

Question on oxidative phosphorylation?

If lactic acid bacteria interfere with oxidative phosphorylation, how does this inhibit growth/development/colonisation of other bacteria...e.g. in yoghurt?

Thank you
by ilovebiology77
Mon Feb 27, 2012 9:21 pm
Forum: Microbiology
Topic: What is the positive control and negative control?
Replies: 9
Views: 9094

Hi again, thanks for the reply. Your suggestions for the positive and negative control are really helpful but I think they make more sense if I was counting the actual spoilage bacteria. I'm counting the lactic acid bacteria so from what I understand about negative and positive controls, I need to k...
by ilovebiology77
Mon Feb 27, 2012 12:34 am
Forum: Microbiology
Topic: What is the positive control and negative control?
Replies: 9
Views: 9094

Re: What is the positive control and negative control?

Hi there, Many thanks for replying! Hmm I thought that if the numbers of lactic acid bacteria are higher, the more lactic acid produced. But... maybe this idea is flawed... The one you mentioned for a control 'buffering the pH toward neuatrality' sounds really good, would this be a positive or negat...
by ilovebiology77
Sun Feb 26, 2012 3:44 pm
Forum: Microbiology
Topic: What is the positive control and negative control?
Replies: 9
Views: 9094

What is the positive control and negative control?

I'm looking at whether the sugar content affects the shelf life in yoghurt. I will count the number of lactic acid bacteria in each sample. The more lactic acid bacteria, the longer the shelf life. My hypothesis is that the higher the sugar yoghurt, the more lactic acid bacteria (preserves yoghurt)....
by ilovebiology77
Sun Feb 26, 2012 12:25 am
Forum: Microbiology
Topic: Sources of bacteria in agar?
Replies: 1
Views: 1126

Sources of bacteria in agar?

Hi there,

so I'm going to grow some bacteria on agar from yoghurt samples but was wondering, apart from the bacteria in yoghurt, what other sources might the bacteria come from?

Which agar could I use so that I only have lactic acid bacteria growing (or what alterations can I make) ?

Many thanks!
by ilovebiology77
Sat Feb 25, 2012 10:35 pm
Forum: Microbiology
Topic: pH indicator in agar plates
Replies: 0
Views: 1343

pH indicator in agar plates

Hi there, I'm about to conduct an experiment where I look at the effect of sugar on the shelf life of yoghurt. I plan to measure this by quantifying the number of lactic acid bacteria in each sample by using bromocresol purple pH indicator. However, before I do the experiment, I was wondering what k...