Effect of caffeine concentration on biomass production, caffeine degradation, and morphology of Aspergillus tamarii

The aim of the present study was to evaluate the effect of the initial caffeine concentration (1–8 g/L) on growth and caffeine consumption by Aspergillus tamarii as well as pellet morphology, in submerged fermentation. Caffeine was used as sole nitrogen source. At 1 g/L of initial caffeine concentration, caffeine degradation was not affected, resulting in a production of 8.7 g/L of biomass. The highest biomass production (12.4–14.8 g/L) was observed within a range of 2 to 4 g/L of initial caffeine concentration. At these initial caffeine concentrations, after 96 h of fermentation, 41–51 % of the initial caffeine was degraded. Using an initial caffeine concentration of 2–3 g/L, the highest specific growth rate was observed (μ = 0.069 1/h). Biomass production decreased at 8 g/L of initial caffeine concentration. A. tamarii formed mainly pellets at all concentrations tested. The size of the pellet decreased at a caffeine concentration of 8 g/L.