You can easily distenguish between LAB and yeast growth on Petri dishes using striking methods to get single colonies. You should examine some colonies microscopically. Most LAB colonies are cream-like colored and shiny but most yeast colonies are skin-like shaped with different colors (white, red, etc...). LAB colonies are rounded whereas most yeast colonies are not rounded exactly. best wishes.
You have to add antibiotics to the medium before you use it for isolation
Thank u very much mr sameh what is yuor idia about adndingum sodium azid to mrs?
Hi!
You can do the plating of LAB in modified MRS5 agar containing 0.05 g/l Bromocresol green and 0.1 g/l cycloheximide. The first compound will allow you distinguish between different LAB colonies, so you can check LAB contaminations (different species will give colonies different in morphology, differences which are made visible by the presence of bromocresol). The second is an antibiotic which inhibits the growth of eucaryotic cells, it will inhibit the yeast growth.
For references:
Dal Bello, F., Hertel, C., 2006. Oral cavity as natural reservoir for intestinal lactobacilli.
Syst. Appl. Microbiol. 29, 69–76.
Meroth, C.B., Walter, J., Hertel, C., Brandt, M.J., Hammes, W.P., 2003b. Monitoring the
bacterial population dynamics in sourdough fermentation processes by using PCRdenaturing
gradient gel electrophoresis. Appl. Environ. Microbiol. 69, 475–482.
Hope it helps
Hi daer Alice thank u very much .whats your idea about best medium for isolation lab from fermented plant?
please use MRS agar for isolation. For identification of LAB you can use catlase test LAB are catlase negative. if u isolating organisms from milk do serial dilution .
MRS is the best media to isolate the lactobacillus.to avoid contamination u change the incubation u keep the plate up to 3 days dont do much incubation and another one thing before u autoclave the media u check the PH.
Check this may it help you:
http://aem.asm.org/content/71/5/2239.full
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