You will kill it with boiling. Probably 170 will do it, maybe even lower.
Would like to know why you are asking so we can tell you if you have a problem. If you want to mash overnight, you might be OK. Lacto has a lag period before it starts working where it acclimatizes itself to it's environment. Seems to be somewhere between 10 and 60 hours ...... however, as soon as someone takes my advice they will find the perfect environment for Lacto, and it will take off immediately.
There are other bacteria in the mash, which might start working quicker and produce undesirable results.