Biotransformation of citral and nerol by spores ofPenicillium digitatum

Abstract

A simple and efficient method was developed to carry out biotransformation reactions on terpenoid compounds. For these experiments spores of Penicillium digitatum were inoculated on solid media in conical flasks. After a short incubation period, the spores germinated and a mycelial culture was formed. After 2 weeks, the cultures had completely sporulated and bioconversion reactions were started. For this purpose a known volume of nerol or citral was sprayed on to the sporulated surface culture. After 1–2 days, a period during which transformation took place, the flasks were fitted with an aeration piece, connected with a tube filled with Tenax. The bioconversion was monitored by dynamic headspace techniques during a period of 8, 24 or 48 hours. Both nerol and citral were transformed into 6-methylhept-5-en-2-one by sporulated surface cultures. The spores retained their activity over prolonged periods, up to 2 months. The overall yield varied from 92% to 99%. © 1998 John Wiley & Sons, Ltd.