Isolation of a new strain of Aspergillus and molecular structure elucidation of unknown metabolite produced from castor oil

Abstract

A new Aspergillus strain BU20S was isolated and identified by sequence analysis of ribosomal internal transcribed spacer (ITS) regions. Unknown metabolite produced by the strain was identified by elucidation of molecular structure using a combination of 13C and 1H NMR, MS, FTIR, XRD, and HPLC analysis. The metabolite was found to be kojic acid, which has the potential to treat methicillin-resistant Staphylococcus aureus (MRSA) infection, among other industrial applications. It was observed that the isolated strain can produce kojic acid from castor oil and product titer can be increased by supplementing the medium with rice straw-derived depolymerized lignin. The substrate concentrations were optimized by response surface methodology using Design-Expert® software. As high as 6.69 ± 0.24 g/L of kojic acid was obtained using castor oil (20 g/L) and depolymerized rice straw lignin (3 g/L). This is the first report on kojic acid production from castor oil.