Kinetic model of hydrogen generation by Rhodobacter sphaeroides in the presence of NH4+ ions

Abstract

Aims: To examine the effects of ammonium ion concentration and illumination intensity on the effectivness of the hydrogen generation process of Rhodobacter sphaeroides. Methods and Results: In all experiments the amount of evolved hydrogen, biomass growth, concentration of ammonium ions, pH and chemical oxygen demand were measured. A nonstructural kinetic model was applied in description of biomass growth, the amount of evolved hydrogen and consumption of organic compounds and ammonium ions. An increase of ammonium ions concentration resulted in a decrease of maximal specific hydrogen potential production. At higher ammonium ion concentrations, no hydrogen evolution was observed. The efficiency of malic acid conversion into hydrogen and the PHB content in the biomass were the highest with lower concentrations of nitrogen compounds. Conclusion: The presence of ammonium ions inhibits hydrogen photogeneration. A good agreement between the experimental data and model simulations were obtained. In all cases, hydrogen evolution started after an exhaustion of ammonium ions and the increase was proportional to the C/N ratio in the medium. The accumulation of PHB competes with the hydrogen evolution process while the conversion of acids into biomass was limited at higher levels of hydrogen generation. Significance and Impact of the Study: Confirmation of the suitability of the selected model for kinetic studies of hydrogen photoevolution.

Photofermentative Hydrogen Generation in Presence of Waste Water from Food Industry

“…In case of brewery waste with low COD (27 g O 2 /l) only 0.67 l of H 2 per l medium was produced (waste concentration 80 % v/v). If higher concentrations of wastes were applied, the efficiency of hydrogen production was lower, which was caused by and inhibiting concentration of N-NH 4 + (40 mg/l for dairy waste and 96 mg/l for brewery waste) (Waligórska, 2009, Melis, 2006. Such concentration of ammonium ions can diminish significantly the overall generation of hydrogen .…”

“…The crude wastes were acidic (dairy waste pH 4.2, brewery waste pH 4.7) and contained high concentration of NH 4 + (40 mg/l dairy waste and 96 mg/l brewery waste), which can significantly reduce hydrogen production (Waligórska, 2009). High concentration of N-NH 4 + as well as N 2 inhibits hydrogen production by nitrogenase.…”

Microbiological Methods of Hydrogen Generation

“…In the presence of molecular nitrogen occurs competitive nitrogen fixation reaction and this stops almost completely hydrogen evolution. Ammonium ions at concentrations higher than 20 μmol are successful but reversible inhibitors of hydrogen generation (Waligórska, 2009) as well. The nitrogen necessary for the cell functioning is usually provided by ethanolamine and glutamate.…”

Estudo de diferentes tipos de fonte de carbono como substrato para produção de hidrogênio por meio de fermentação escura e fotofermentação

“…O íon amônio (NH4 + ) inibe a síntese de nitrogenase, promovendo a formação da glutamina sintetase, responsável pela assimilação de NH4 + , inibindo desta forma a síntese de H2 (SEIFERT, WALIGORSKA e LANIECKI, 2010). Waligórska et al (2009) estudaram os efeitos de íons NH4 + na produção de H2 por R. sphaeroides e observaram que o aumento na concentração de 1 para 5 mmol/L de NH4 + resultou em um declínio na produção de H2. Capítulo 3 -Revisão Bibliográfica…”