When using a preculture with Ampicillin in my protein expression, I have to get rid of the preculture medium to avoid carrying over too much beta-lactamases that will destroy the ampicillin in the main culture. To do this I pellet the cells and resuspend.

Which methods of resuspension are best suited if you need the bacteria alive afterwards? I'm not sure how much force I can apply without harming the bacteria, and resuspending very gently takes a very, very long time.

Which methods can be used to resuspend bacteria alive, and which ones are the fastest?