Is there evidence that samples are safe at -70C?
Spoiler alert - YES! If you've been following My Green Lab, you know that we coined the phrase '-70 is the new -80'. Adjusting your ultra low temperature freezer set point to -70C can reduce energy consumption by 30-40% and prolong the lifetime of a compressor-based freezer. For years we've been directing people to check out the incredible crowd-sourced document, that Dr. Kathy Ramirez-Aguilar at CU Boulder put together, of samples that have been stored at -70C. And now, thanks to our collaboration with the European organization EGNATON on the Freezer Challenge, we have been made aware of these two publications, which show sample stability at -70C for yeasts and molds, and the enzyme PON1. Furthermore, suppliers such as GE and Qiagen have updated their storage recommendations to -70C for certain reagents as well.
The community is still working on obtaining evidence for a wide range of samples - shout out to Martin Farley at Kings College and Amorette Getty at UC Santa Barbara for doing this work - but it's clear the evidence is mounting in favor of safe, sustainable sample storage at -70C.
If you choose to set your ULT freezer to -70C as part of the Freezer Challenge be sure to add your name and your samples to the Google doc! We would also be happy to add them for you - just email us at firstname.lastname@example.org.