Enhanced hexadecane degradation and low biomass production by Aspergillus niger exposed to an electric current in a model system

The effects of an electric current on growth and hexadecane (HXD) degradation by Aspergillus niger growth were determined. A 450-mL electrochemical cell with titanium ruthenium-oxide coated electrodes and packed with 15 g of perlite (inert biomass support) was inoculated with A. niger (2.0 × 107 spores (g of dry inert support)−1) and incubated for 12 days (30 °C; constant ventilation). 4.5 days after starting culture a current of 0.42 mA cm−2 was applied for 24 h. The current reduced (52 ± 11%) growth of the culture as compared to that of a culture not exposed to current. However, HXD degradation was 96 ± 1.4% after 8 days whereas it was 81 ± 1.2% after 12 days in control cultures. Carbon balances of cultures not exposed to current suggested an assimilative metabolism, but a non-assimilative metabolism when the current was applied. This change can be related to an increase in total ATP content. The study contributes to the knowledge on the effects of current on the mycelial growth phase of A. niger, and suggests the possibility of manipulating the metabolism of this organism with electric current.