Appears to partially substitute for Brp function in retinal biosynthesis during bacteriorhodopsin production. Probably catalyzes the cleavage of beta-carotene at its central double bond (15,15') to yield two molecules of all-trans-retinal. all-trans-beta-carotene + O2 = 2 all-trans-retinal In-frame deletion of blh reduces bacteriorhodopsin accumulation on solid medium but not in liquid. However, deletion of both brp and blh completely abolishes bacteriorhodopsin and retinal production in liquid medium, without affecting bacterioopsin accumulation, and the level of beta-carotene is increased by 5.3-fold. Belongs to the Brp/Blh beta-carotene diooxygenase family. Truncated N-terminus.