Epigenetic reversal of some inhibitory histone marks at the promoter region of the enzyme? Driven by some yet-to-be-discovered signaling cascade induced by rein

Epigenetic reversal of some inhibitory histone marks at the promoter region of the enzyme? Driven by some yet-to-be-discovered signaling cascade induced by reintroduction of lactose and proliferation of lactose loving microbes? Just spitballing, this is pure speculation, but is plausible.