Storing yeast

I'm in China and getting HB supplies from the US isn't easy. We're moving our small operation to our friend's restaurant and trying to pump out at least 20gal a week.

I bought a 500g package of Fermentis Safale US-05. On the box it says "Opened packs to be used within 7 days." I'm obviously not going to be able to brew 25 batches in 7 days. Is all of that unused yeast going to go to waste? Is there a way that we can safely store it? Do we need some high tech vacuum seal system? Afraid I may not be able to find such a thing here. Any advice would be very much appreciated!

For storage of the unused part of the 500g package as long as it stays cold and dry you should be okay. A zip lock vacuum bag or a food saver bag would be ideal.

Harvesting the yeast after fermentation might be a good idea:
http://woodlandbrew.blogspot.com/2013/01/yeast-storage.html

Or you could propagate the yeast and pitch part of it and store the rest. There is a good link for how to do that on this site. I'll try to dig it up, but someone else will probably beat me to it.

I would...

Empty the contents into a sanitized jar and store in fridge.

Or fold the foil pack over several times and secure with binder clips. Double bag with zip lock bags. Store in fridge.

Either of those ways, you should be good for a month or three.

Great. I think I'll try the double zip lock bag thing. Should be able to use it all up in 3 months!