dreikus, good question. For our American friends, -30C is -22F (the two scales cross at -40, -40F = -40C)
I think your freeze dried cultures should be fine, I keep all mine in kitchin freezer, albeit nowhere near that cold. There's some Product Data Sheets in our Library, you could check there. Also, how about contacting your supplier?
But your rennet, assuming liquid could be a problem, first if glass bottle then probably broken, second I don't know how liquid rennet if frozen and thawed.