Involved in the biosynthesis of the major C30 carotenoid methyl 4'-[6-O-(acylglycosyl)oxy]-4,4'-diapolycopen-4-oic acid via 4,4'-diapolycopen-4-oic acid intermediate. Catalyzes the oxidation of 4,4'-diapolycopen-4-al to yield 4,4'-diapolycopen-4-oic acid. A + all-trans-4,4'-diapolycopen-4-al + H2O = AH2 + all-trans-4,4'-diapolycopen-4-oate + H(+) Carotenoid biosynthesis. Belongs to the carotenoid/retinoid oxidoreductase family. CrtN subfamily.