Catalyzes the introduction of C-3,4 double bonds into 1-hydroxyneurosporene (1-HO-Neu) to yield demethylspheroidene (DMS). The preferred substrates are 1-hydroxy-neurosporene, 1-hydroxy-lycopene and 1,1-dihydroxyneurosporene, however the 3,4-didehydrolycopene derivatives such as 1,1-dihydroxy-3,4-didehydrolycopene, 1-methoxy-1-hydroxy-3,4-didehydrolycopene and 1-hydroxy-3,4-didehydrolycopene are also efficiently converted. 1-HO-carotene derivatives can be also used. A + rhodopin = (3E)-3,4-didehydrorhodopin + AH2 Carotenoid biosynthesis; spheroidene biosynthesis. Belongs to the carotenoid/retinoid oxidoreductase family.