Cheaper cell harvesting methods?

[jarlemag]

Hi. I'm in the process of buying equipment to set up a basic "DIY bio" lab. I have most of the items needed, but I haven't been able to afford a proper centrifuge yet.  The "Dremelfuge" and similar DIY setups are certainly interesting, but I am not comfortable relying on such solutions because of safety concerns. So I'm wondering - is there a cheaper alternative to centrifugation for pelleting/harvesting bacterial cultures? Does anyone have experience with using filtering for cell culture harvesting? I did a quick search, and found this one article as an example: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC291564/ 

Is filtration a reasonable alternative to centrifugation for cell culture harvesting in DIY bio labs?

A second question: I do have a benchtop "ultramicro"-centrifuge for spinning down Eppendorf tubes. Does anyone have experience with using these with spin columns? Can the lower RPM be offset by longer centrifugation times, or are they just too weak?

Best regards,

Jarle Pahr

[shamrock]

I would go for a proper "eppendorf" or similar microfuge which you should be able to pick up for as little as $100 or so on e-bay. Most have an adjustable speed setting that will allow you to go from 1K rpm to around 14K (about 17K g). You could go the filtration route, most of the spin column chemistries work well using a vacuum to move materials through the columns, but you would have to get a vacuum source and rig up a manifold to hold the columns and tubes. You also have to worry about filter clogging, especially if your filtering dense bacterial or yeast cultures.  A microfuge will give you much more flexibility and be more useful. You don't need a large centrifuge-one capable of handling the 1.8ml microfuge tubes is all you need for typical DIY operations. They typically come with 12 - 18 place rotors.

I haven't tried the small bubble looking minifuges for pelleting cells, don't know what g forces they generate. You probably could harvest cells with them but would most likely have to centrifuge for longer. Its easy to test and might even work with the spin columns.

[jarlemag]

Thanks for the suggestions. I was thinking that centrifuging in Eppendorf tubes would give too little culture volume, but I suppose I can pool the pellets after centrifuging to get around that with a slight amount of extra work. 

Anyone else have any experiences?

Best regards,
JP

[Mike Horwath]

Hi JP,

Working in an academic lab, I often pellet E.coli at 2500G for 30 min.  This is lower  speed than "reccomended" but it works fine for me.  I imagine it depends on the relative density of your bacteria and media.  If I'm using the E.coli for a plasmid prep, eventually i need higher speed to pellet the plasmid.  At that point I will divide the liquid into eppendorf tubes and use the microfuge.  Splitting and re-pooling works fine, just takes more time.

Mike

[jarlemag]

Thanks for sharing your experience. I've previously used the Promega Wizard SV miniprep kit, which specified 5 minutes at 10 000 G to pellet the culture. For the later steps, the protocol specifies "maximum speed/about 14 000 g" in a microcentrifuge. It appears that mini-centrifuges give about 6000 rpm and 2000g...

Best regards,

Jarle Pahr