Catalyzes the double cyclization reaction which converts lycopene to beta-carotene (PubMed:7550379, PubMed:20460582). Catalyzes the double cyclization reaction which converts neurosporene to 7,8-dihydro-beta-carotene (PubMed:20460582). a carotenoid psi-end group = a carotenoid beta-end derivative all-trans-lycopene = gamma-carotene gamma-carotene = all-trans-beta-carotene all-trans-neurosporene = beta-zeacarotene beta-zeacarotene = 7,8-dihydro-beta-carotene Binds 1 FAD per subunit non-covalently. Carotenoid biosynthesis; beta-carotene biosynthesis. Carotenoid biosynthesis; beta-zeacarotene biosynthesis. Monomer. Belongs to the lycopene cyclase family.