A novel multi-stage preculture strategy of Rhizopus oryzae ME-F12 for fumaric acid production in a stirred-tank reactor

This study has developed a novel multi-stage preculture strategy to control the morphology of filamentous Rhizopus oryzae in a 3.3-l stirred-tank reactor (STR), consequently enhancing the fumaric acid production. Using multi-stage precultures as inoculum, the morphology of R. oryzae was maintained as large clumps, small fluffy pellets, and entangled filaments. The highest fumaric acid production of 42.5 g/l with a yield of 55.6% was obtained in association with the small fluffy pellets which were formed in the third preculture at pH 3.0. The results indicated that the use of the multi-stage precultures as inoculum in the STR is a promising approach for commercial production of fumaric acid.