Involved in the biosynthesis of the acyclic C50 carotenoid bacterioruberin (BR). Catalyzes the reaction that introduces hydroxyl groups to C3'' and C3''' of bisanhydrobacterioruberin (BABR) to generate BR. bacterioruberin = bisanhydrobacterioruberin + 2 H2O Carotenoid biosynthesis. Cells lacking this gene accumulate BABR. Belongs to the BABR hydratase family.