Rhizopus oryzae and Rhizopus microsporus strains were screened for their ability to produce fumaric acid on glycerol
as the sole carbon source in the medium. After seven days of stationary culture, fumaric acid was assayed
by HPLC analysis, and maximum concentrations of 0.3% (w/v) and 0.33% (w/v) were recorded. Protoplast fusion
was used to improve fumaric acid production. A selective medium for the fusant culture was composed on the
basis of biochemical differences between parental strains, as examined using the Biolog FF MicroPlate^TMFungi
Identification Test. Double fusion rounds led to a 1.46-fold increase in fumaric acid productivity relative to the
parental strains. Individual Rhizopus fusants demonstrated a various ability to produce fumaric acid from
2.0% (w/v) of glycerol, with the most effective ones producing from 0.2 to 0.27 g · g^-1 this acid. To date, no studies
have been carried out to improve fumaric acid production by Rhizopus with the use of glycerol as the only
carbon source in the medium.