What temperature should I use for expressing thermophillic genes in E. coli?

I am currently working with E.coli and I am trying to express thermophilic genes. What temperature should I be using for incubation after IPTG induction? I have read some papers that suggested to incubate the cells at 42 degrees for a short amount of time. Is this going to affect the protein?

Experiment: Protein expression and purification Bacteria - Bacillus subtilis GCSF