Table 2.

The change of pH after sulfide oxidation

Strains	pH
	Initiation	First cycle	Second cycle	Third cycle
G. oxydans 621H	7.38 ± 0.03	7.67 ± 0.10	7.97 ± 0.15	8.17 ± 0.15
P. putida S16	7.13 ± 0.06	7.43 ± 0.12	7.67 ± 0.06	7.95 ± 0.05

The experiments were carried out in the 50-mL centrifuge tube containing 10 mL of 0.9% NaCl and magnetically immobilized cells at 30 °C, 180 rpm. NaHS was added to 2 mM to initiate the reaction in each cycle and the pH was tested at the beginning and the end of each cycle