Metabolic engineering of Rhizopus oryzae: Effects of overexpressing fumR gene on cell growth and fumaric acid biosynthesis from glucose

► We overexpressed fumarase encoded by fumR in Rhizopus oryzae. ► The transformants showed 5-10-fold increase in fumarase activity compared to the wild type. ► The effect of overexpressing fumR on fumaric acid production was investigated. ► Fumarase overexpression yielded more malic acid, instead of fumaric acid, in the fermentation. ► This is because the fumarase also catalyzes the hydration of fumaric acid to malic acid.