Ways to covering Erlenmyer flasks ??? - (Apr/29/2010 )

I am about to start an experiment that requires 50 x Erlenmeyer flask to culture slow growing bacteria in an orbital shaker for 5-6weeks. I would normally just use a flask with a screw cap, but since I don't have enough I will be using the open mouth variety. I'm not sure of the best way to protect my cultures from contamination during such a long incubation? I really want to avoid foil and cotton wool, but don't know what alternatives will work.

Also, one suggestion that has come up on a random search of the www suggested transparent adhesive film dressing used in wound care as an options. Does anyone know if this would work?

Thanks in advance! M

what about aluminum foil sealed with adhesive tape?

why avoid foil?

can you try parafilm ? if you are scared of contamination, put parafilm under UV for sometime.

why avoiding cotton wool? If you have proper cotton plugs you can keep cultures shaking forever without contamination! I would not use aluminium foil or parafilm, the risk that they fall off is too high.

If you still want to avoid cotton, there are cellulose plugs available, they work well.

Is parafilm gas permeable enough for long-term cultures?

I would not use parafilm; it gets brittle and the risk that it is falling off when people are entering and leaving or solely because of shaking is very high; really crucial will be micro-holes. These risks are way too high to use it for such a long running experiment. Too much time lost when going back to the start.

Thanks for the suggestions and comments!

Normal I would not be so worried and just give any old idea a try and see how it works out ... but.... I have only a 8 week window of opportunity to use the teaching labs large orbital shakers in my lab's 28oC room. After this window closes, I won't have access to a large orbital shaker until November and (more importantly) I will lose the 28oC room during renovations starting in September and I will have to run the flasks 6 at a time on our lab's tiny orbital shaker. So getting this right the first time is going to be critical.

Foil: I don't want to use foil because it tends to deform over time due to the shaking process and I have sometimes had contamination when using it before. Securing it with tape might help with that.

Parafilm: It tends to breakdown over time and as a result I have had problems with contamination in the past. I've thought about placing a non-stretched peice of parafilm over the top and securing the over hanging edges with peices of parafilm. Breakdown (within 2 months) tends to be more of an issue with stretched parafilm but I'm not sure if the gas exchange will still be effective.

Cotton wool: This is a possility if it is done correctly. However, a couple of months back we had an issue with humidity in our lab. As a result another persons cottom plug basically got moist and the flask became contaminated. I don't have a lot of cofindence the the plug was that well secured in the first place, but I has made me a be cautious. Are there any suggestion on the best methods for creating great cotton wool plug?

Cellulose plugs: I haven't heard of these before, but they do look promising. I managed to find one company in Germany that manufactured them. Gebirgsziege, do you know of many suppliers or alternatively product names for these stoppers?

Cheers
M

Sterile gauze dressings held by an elastic band?

Can you find some deep steel containers that will be large enough to sit on top of the flasks similar to the caps on tubes?

gebirgsziege on Apr 29 2010, 09:19 PM said:

I agree with gb. Sterilise the flasks with the cotton wool plugs (of there are foam plugs you can also use called Identi-plugs, there are a number of suppliers) in place (wrap the plugs in gauze beforehand). There should be a couple of cm of the plug over the top of the flask. cover the plugs with foil, to avoid water drops during autoclaving getting into the cotton wool.