Biotransformation of geraniol, nerol and citral by sporulated surface cultures of Aspergillus niger and Penicillium sp.

The biotransformation of geraniol, nerol and citral by Aspergillus niger was studied. A comparison was made between submerged liquid, sporulated surface cultures and spore suspensions. This bioconversion was also carried out with surface cultures of Penicillium sp. The main bioconversion products obtained from geraniol and nerol by liquid cultures of A. niger were linalool and alpha-terpineol. Linalool, alpha-terpineol and limonene were the main products obtained from nerol and citral by sporulated surface cultures, whereas geraniol was converted predominantly to linalool, also resulting in higher yields. Bioconversion of nerol with Penicillium chrysogenum yielded mainly alpha-terpineol and some unidentified compounds. With P. rugulosum the major bioconversion product from nerol and citral was linalool. The bioconversion of nerol to alpha-terpineol and linalool by spore suspensions of A. niger was also investigated. Finally the biotransformation with sporulated surface cultures was also monitored by solid phase microextraction (SPME). It was found that SPME is a very fast and efficient screening technique for biotransformation experiments.