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

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 elucida-tion 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 iso-lated 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 (R) 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.(c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.