Kinetics and modelling of thiosulphate biotransformations by haloalkaliphilic Thioalkalivibrio versutus

Abstract

<p>Biotransformation of thiosulphate by Thioalkalivibrio versutus was studied under haloalkaline conditions (pH 10, 0.66–1.2 M Na<sup>+</sup>) using batch assays and modelling tools for possible sulphur recovery from haloalkaline industrial streams. The thiosulphate was fully biotransformed to sulphate or to sulphate and elemental sulphur at initial S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S concentrations of 25–550 mM within 10 days. The highest biotransformation rate of 2.66 mM [S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S] h<sup>−1</sup> was obtained at initial S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S concentration of 550 mM with half saturation constant (K<sub>s</sub>) of 54.5 mM [S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S]. At initial concentrations below 100 mM S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S, the main product was sulphate whilst at above 100 mM also elemental sulphur was produced with up to 29% efficiency. The model approach developed incorporated S<sub>2</sub>O<sub>3</sub><sup>2−</sup> biotransformation to SO<sub>4</sub><sup>2−</sup> and S<sup>0</sup>. The kinetic modelling results were compatible (R<sup>2</sup> > 0.90) with the experimental data. The maximum growth rate (µ<sub>m</sub>) was 0.048 h<sup>−1</sup> (0.47 mM C<sub>5</sub>H<sub>7</sub>NO<sub>2</sub> h<sup>−1</sup>) and the maximum growth yield 0.18 mM C<sub>5</sub>H<sub>7</sub>NO<sub>2</sub>/mM S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S (20 g cell/mol S<sub>2</sub>O<sub>3</sub><sup>2−</sup>-S). The high rate thiosulphate biotransformation and elemental sulphur recovery results together with the developed kinetic model can be used for bioprocess design and operation. The potential industrial applications would aim at sustainable resource recovery from industrial haloalkaline and sulphurous process and/or effluent streams.</p>