Prevention of melanin formation during aryl alcohol oxidase production under growth-limited conditions using an Aspergillus nidulans cell factory

•Melanization of A. nidulans was detrimental for enzyme production.•Copper and zinc in media stimulated pigment formation in growth-limited cultures.•Removal of copper from media resulted in 48% increase in AAO production.•Ascorbic acid reduced melanin formation and increased enzyme activity.•A modi...

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Bibliographic Details
Published in:Bioresource technology 2017-11, Vol.243, p.874-882
Main Authors: Pardo-Planas, Oscar, Prade, Rolf A., Müller, Michael, Atiyeh, Hasan K., Wilkins, Mark R.
Format: Article
Language:English
Subjects:
Alcohol Oxidoreductases - metabolism
Ascorbic Acid
Aspergillus nidulans
Bioreactors
Enzyme production
Melanin
Melanins
Monophenol Monooxygenase
Pigmentation
Trickle bed reactor
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Summary:•Melanization of A. nidulans was detrimental for enzyme production.•Copper and zinc in media stimulated pigment formation in growth-limited cultures.•Removal of copper from media resulted in 48% increase in AAO production.•Ascorbic acid reduced melanin formation and increased enzyme activity.•A modified medium was developed to decrease pigmentation in our A. nidulans strain. An Aspergillus nidulans cell factory was genetically engineered to produce an aryl alcohol oxidase (AAO). The cell factory initiated production of melanin when growth-limited conditions were established using stationary plates and shaken flasks. This phenomenon was more pronounced when the strain was cultured in a trickle bed reactor (TBR). This study investigated different approaches to reduce melanin formation in fungal mycelia and liquid medium in order to increase the enzyme production yield. Removal of copper from the medium recipe reduced melanin formation in agar cultures and increased enzyme activities by 48% in agitated liquid cultures. Copper has been reported as a key element for tyrosinase, an enzyme responsible for melanin production. Ascorbic acid (0.44g/L) stopped melanin accumulation, did not affect growth parameters and resulted in AAO activity that was more than two-fold greater than a control treatment with no ascorbic acid.
ISSN:0960-8524
1873-2976
DOI:10.1016/j.biortech.2017.06.183