NH+/4-N assimilation by Rhodobacter capsulatus ATCC 23782 grown axenically and non-axenically in N and C rich media

Assimilation of NH+/4-N and formation of cell biomass in Rhodobacter capsulatus ATCC 23782 were studied in batch cultures as a function of N and C concentration and light intensity. Growth occurred satisfactorily up to N and C levels of 1.2 and 6.0g/1, respectively. The maximum biomass density achieved was 2.3 g biomass-C/l at 0.8 g N/l and 4.0g C/l. Media containing initial C/N ratios of 5 provided good growth and almost complete assimilation and recovery of NH+/4-N and lactate-C, respectively. A light intensity of about 120 μE/m²/s was adequate for efficient growth. At low levels of NH+/4-N (<0.05 g N/l), the photobacterium could not maintain dominance under non-axenic growth conditions. Chloroxuron was necessary to prevent algal overgrowth. At concentrations of 0.2 and 0.4 g NH+/4-N/l, the photo-bacterium maintained dominance over several months under the appropriate conditions of temperature (30°C), light intensity (120μE/m²/s), carbon supply (C/N = 5) and cell residence time (5.5d). The protein of Rhb. capsulatus ATCC 23782 was rich in essential amino acids.