Choosing Selective Agar Medias

Monday Lab Prep
Made up three different media agars to promote the selective growth of Brettanomyces spp. and use for enumeration. I will test these out with the currently propagating cultures and save them for further use throughout the study to confirm my fermentations are uniquely Brettanomyces spp. The three media agars I chose to prepare were MYPG with an addition of 10 ppm cycloheximide (actidione), Copper Sulfate (CuSO4) and Lysine agar. These three mediums should inhibit the growth of any Saccharomyces yeasts which could be present, and allow me to obtain a pure culture usable throughout the rest of the study. The ingredients for making up the plates are listed below.

MYPG+cycloheximide(10 ppm) agar – 500 ml
Malt extract 1.5 g
Yeast extract 1.5 g
Peptone 1.0 g
Glucose 5 g
Agar 7.5 g
Cycloheximide 5 mg (10 ppm=10 mg/l in .5 l=5 mg)
*pH adjusted to 5.0

Copper Sulfate agar – 500 ml
Malt extract Agar 50.0 g
Copper Sulphate 0.6 g
*Autoclaved at 115°C for 10 minutes

Lysine agar – 500 ml
Glucose (1%)  5 g
L-Lysine (1%)  5 g
Agar (1.2%)  6 g
Yeast salts 0.5 ml
*pH adjusted to 6.0
*Autoclaved at 121°C for 15 minutes at 15 psi
*Add vitamin solution once cooled to pouring temp – 1 ml/l

As always the plates were dried in the plate pouring room and I will be ready to streak and pipette inoculate some of them tomorrow. For anyone interested in reading on selective culturing of any brewing bugs “Brewing Microbiology” by F.G. Priest has the information on page# 378-382. I highly recommend having a look through this book for all aspects on the microbiology involved in brewing.

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~ by Chad on February 16, 2009.

 
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