Hydroxylamine-O-sulphonic acid

Endpoint summary

Additional information

The test substance Hydroxylamine-O-sulphonic acid is an inorganic compound.

Summary according the biological degradation of Bis(hydroxyl)ammonium sulphate (in EU-RAR Draft, 14. May 2008)

Since no data are available for the test substance, a read-across was done to the inorganic source/surrogate substance Bis(hydroxylammonium)sulphate due to structural similarity.

The surrogate substance Bis(hydroxylammonium)sulphate is not an organic molecule. Mineralisation is defined as the process of biological degradation to stable inorganic products. According to this definition, biodegradation of bis(hyroxylammonium)sulfate is not possible and of no importance. A test on estimation of the biochemical oxygen demand was submitted indicating no oxygen demand within 5 days. In the study protocol it was concluded that a concentration of 5 mg/l and more might inhibit microbial activity. However, due to insufficient documentation the test is not acceptable.

Independent of the acceptance of this study, other findings (e.g. Amarger & Alexander 1968), also indicate an inhibition of microbial activity due to high concentration of hydroxylamine.

However, hydroxylamine is a natural intermediate in biological nitrification under aerobic conditions (Amarger and Alexander 1968). The chemolithoautotrophic growth is obtained by the oxidation of ammonia to nitrite. This is a two-step process. The first step involves the

oxidation of ammonia to hydroxylamine by the membrane bound enzyme ammonia monooxygenase in the following reaction:

NH₃+ O₂ + 2e^- + 2H⁺ --> NH₂OH + H₂0 

In the second step, the intermediate, hydroxylamine, is oxidized to nitrite by the enzyme hydroxylamine oxidoreductase (HAO) in the following reaction:

NH₂OH + H₂O -->  NO₂^-+ 4e^- + 5H⁺   (Arciero and Hooper 1993).

For several chemolithoautotrophic bacteria, such as Nitrosomas europea, Nitrosomas nitrosa and Nitrosococcus oceanus, mixotrophic growth on hydroxylamine in the presence of ammonia has been demonstrated (Böttcher and Koops 1994, de Brujin et al. 1995). The molar growth yield on hydroxylamine, measured as a formation of cell protein per unit substrate oxidized, was found to be approximately twice that of ammonia. In respiration experiments, the oxygen consumption was 1.5 mol O₂ per mol ammonia and 1.0 mol O₂ per mol hydroxylamine oxidized to nitrite (Böttcher and Koops 1994). For N. europea molar growth yield was considerably high (4.74 g mol^-1 at a growth rate of 0.03 h^-1). Anaerobic growth of N. europea on hydroxylamine and ammonium was not observed (de Brujin et al. 1995). Furthermore, hydroxylamine may be used as an additional energy source in heterotrophic nitrifying bacteria such as Pseudomonas PB16 (Jetten et al. 1997). For the latter, a maximum specific hydroxylamine oxidizing activity of 450 nmol min^-1 mg dry weight^–1, with a Ks of approximately 40 µM, has been determined.

In high concentrations, inhibition of bacteria by the dissociation products is possible.

References:

Amarger N, Alexander M (1968). Nitrite formation from Hydroxylamine and oximes by Pseudomonas aeruginosa. J Bact 95(5): 1651-1657

Arciero DM, Hooper AB (1993). Hydroxylamine oxidoreductase from Nitrosomonas europaea is as multimer of an octa-hem subunit. J Bact Chemistr 268(20): 14645-14654

Böttcher B, Koops HP (1994). Growth of lithotrophic ammonia-oxidizing bacteria on hydroxylamine. FEMS Microbiol Lett 122: 263-266

De Brujin P et al. (1995). Growth of Nitrosomonas europaea on hydroxylamine. FEMS Microbiol Lett 125: 179-184

Jetten SM et al. (1997). Hydroxylamine metabolism in Pseudomonas PB16: involvement of a novel hydroxylamine oxidoreductase. Antonie van Leeuwenhoek 71: 69-74

ECB (2008). EU-RAR Draft, Bis-(hydroxylammonium)sulphate, CAS: 10039 -54 -0,14. May 2008