With the new FAQ regarding two-handed weapons and power attack:
FAQ
Power Attack: If I am using a two-handed weapon with one hand (such as a lance while mounted), do still I get the +50% damage for using a two-handed weapon?
Yes.
Does this supersede Jotungrip or is jotungrip an exception to this new ruling?
Jotungrip (Ex)
At 2nd level, a titan mauler may choose to wield a two-handed melee weapon in one hand with a –2 penalty on attack rolls while doing so. The weapon must be appropriately sized for her, and it is treated as one-handed when determining the effect of Power Attack, Strength bonus to damage, and the like.