Biotransformation of dopamine to norlaudanosoline by Aspergillus niger

Abstract

Abstract Norlaundanosoline is a key intermediate in the synthesis of the benzylisoquinoline alkaloids providing the upper isoquinoline portion of the morphinan skeleton . This study evaluates the feasibility of using Aspergillus niger as an in situ biotransformation system to produce norlaudanosoline from dopamine. A. niger was chosen because monoamine oxidase can be readily induced in this organism. Monoamine oxidase catalyzes the conversion of dopamine to 3,4‐dihydroxyphenylacetaldehyde. In the presence of dopamine, this aldehyde will then undergo a spontaneous Picket‐Spengler condensation to form norlaudanosoline. Fermentation condition to form norlaudanosoline. Fermentation conditions were optimized for the production monoamine oxidase by using a two‐stage process consisting of a growth stage and an induction stage. pH control was found to be important, and at pH 4.5 dopamine accumulation in the cells was high as was the level of monoamine oxidase. With pH control at 4.5, up to 21% of the cellular dopamine was converted to norlaudanosoline. It is proposed that with further protein engineering improvements, this system may prove suitable for the in situ bio‐transformation of dopamine to norlaudanosoline.