Protoplast fusion of Rhizopus oryzae and Rhizopus microsporus for enhanced fumaric acid pr

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 Fungi 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 of 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.