Caffeine degradation in solid state fermentation by Aspergillus tamarii: Effects of additional nitrogen sources
Résumé
The ability of Aspergillus tamarii V12A25 to use caffeine as sole nitrogen source was investigated in solid state fermentation (SSF) using two different supports, polyurethane foam (PUF) and sugarcane bagasse. Caffeine can be used in SSF as the sole nitrogen source, the carbon source being saccharose. If a simpler nitrogen source (ammonium sulphate, urea) is added to the medium containing caffeine, this source will be used first allowing fungal growth. If saccharose is still present when the simple nitrogen source has been degraded, caffeine will be used as the nitrogen source, together with saccharose. Caffeine at a concentration of 8 g/l has no effect on fungal growth when a simple nitrogen source is not limiting. The main difference between the two solid supports was the time required to complete the fermentation. With sugarcane bagasse as the support, substrates (caffeine, ammonium sulphate, urea) were degraded almost twice as fast as with PUF as the support. Theophylline and 3-methylxanthine, the major products from caffeine degradation, disappeared completely from the culture medium shortly after caffeine degradation stopped. The major advantage of using PUF support over sugar cane bagasse is that the former allows determination of fungal biomass which is not possible with the latter.