Bacterial based remediation of environmental toxicants is a promising innovative technology for molybdenum pollution. To date, the enzyme responsible for molybdate reduction to Mo-blue from bacteria show that the Michaelis-Menten constants varies by one order of magnitude. It is important that the constants from newer enzyme sources be characterized so that a comparison can be made. The aim of this study is to characterize kinetically the enzyme from a previously isolated Mo-reducing bacterium; Bacillus pumilus strain Lbna. The maximum activity of this enzyme occurred at pH 5.5 and in between 25 and 35 oC. The Km and Vmax of NADH were 6.646 mM and 0.057 unit/mg enzyme, while the Km and Vmax of LPPM were 3.399 mM and 0.106 unit/mg enzyme. The results showed that the enzyme activity for Bacillus pumilus strain Lbna were inhibited by all heavy metals used. Zinc, copper, silver, chromium, cadmium and mercury all caused more than 50% inhibition to the Mo-reducing enzyme activity with copper being the most potent with an almost complete inhibition of enzyme activity observed.

Molybdenum is an emerging pollutant. Bioremediation of this heavy metal is possible by the mediation of Mo-reducing bacteria. These bacteria contain the Mo-reducing enzymes that can conver toxic soluble molybdenum into molybdenum blue; a less soluble and less toxic form of the metal. To date only the enzyme has been purified from only one bacterium. The aim of this study is to purify the Mo-reducing enzyme from a previously isolated Mo-reducing bacterium Bacillus pumilus strain Lbna using ammonium sulphate fractionation followed by ion exchange and then gel filtration. Two clear bands were obtained after the gel filtration step with molecular weights of 70 and 100 kDa. This indicates that further additional purification methods need to be used to get a purified fraction. Hence, additional steps of chromatography such as hydroxyapatite or chromatofocusing techniques can be applied in the future.