Biodegradation of high concentrations of hexadecane by Aspergillus niger in a solid-state system: Kinetic analysis

Solid-state microcosms were used to assess the influence of constant and variable C/N ratios on the biodegradation efficiency by Aspergillus niger at high hexadecane (HXD) concentrations (180–717 mg g−1). With a constant C/N ratio, 100% biodegradation (33–44% mineralization) was achieved after 15 days, at rates increasing as the HXD concentration increased. Biomass yields (YX/S) remained almost independent (∼0.77) of the carbon-source amount, while the specific growth rates (μ) decreased with increasing concentrations of HXD. With C/N ratios ranging from 29 to 115, complete degradation was only attained at 180 mg g−1, corresponding to 46% mineralization. YX/S diminished (∼0.50 units) as the C/N ratio increased. The highest values of μ (1.08 day−1) were obtained at low C/N values. Our results demonstrate that, under balanced nutritional conditions, high HXD concentrations can be completely degraded in solid-state microcosms, with a negligible (<10%) formation of by-products.