Kinetics of Molybdenum Reduction to Molybdenum Blue byBacillussp. Strain A.rzi

Abstract

Molybdenum is very toxic to agricultural animals. Mo-reducing bacterium can be used to immobilize soluble molybdenum to insoluble forms, reducing its toxicity in the process. In this work the isolation of a novel molybdate-reducing Gram positive bacterium tentatively identified as Bacillus sp. strain A.rzi from a metal-contaminated soil is reported. The cellular reduction of molybdate to molybdenum blue occurred optimally at 4 mM phosphate, using 1% (w/v) glucose, 50 mM molybdate, between 28 and 30°C and at pH 7.3. The spectrum of the Mo-blue product showed a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of bacterial electron transport system (ETS) such as rotenone, sodium azide, antimycin A, and potassium cyanide could not inhibit the molybdenum-reducing activity. At 0.1 mM, mercury, copper, cadmium, arsenic, lead, chromium, cobalt, and zinc showed strong inhibition on molybdate reduction by crude enzyme. The best model that fitted the experimental data well was Luong followed by Haldane and Monod. The calculated value for Luong's constants p max, K s, S m, and n was 5.88 μmole Mo-blue hr−1, 70.36 mM, 108.22 mM, and 0.74, respectively. The characteristics of this bacterium make it an ideal tool for bioremediation of molybdenum pollution.

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND GLYPHOSATE-DEGRADING Klebsiella oxytoca STRAIN SAW-5 IN SOILS FROM SARAWAK

“…Therefore, K. oxytoca strain Saw-5 is a potential candidate for soil bioremediation of sites containing elevated levels of molybdenum either locally or in other tropical countries. The optimum temperature observed in this work falls within the optimal temperature range reported in the majority of the molybdenum reducers isolated to date, which exhibit optimal temperature of between 25 and 37ºC (Shukor and Syed, 2010;Lim et al, 2012;AboShakeer et al, 2013;Othman et al, 2013;Halmi et al, 2013;Khan et al, 2014; with the only psychrotolerant reducer isolated from Antartica showing an optimal temperature supporting reduction of between 15 and 20 ºC .…”

“…The characteristics neutrophiles are their ability to grow between pH 5.5 and 8.0. An important observation regarding molybdenum reduction in bacteria is the optimal pH reduction is slightly acidic with optimal pHs ranging from pH 5.0 to 7.0 (Shukor and Syed, 2010;Lim et al, 2012;Abo-Shakeer et al, 2013;Ahmad et al, 2013;Othman et al, 2013;Halmi et al, 2013;Khan et al, 2014;. It has been suggested previously that acidic pH plays an important role in the formation and stability of phosphomolybdate before it is being reduced to Mo-blue.…”

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND PHENOLIC- AND CATECHOL-DEGRADING Enterobacter sp. STRAIN SAW-2

“…High phosphate concentrations inhibit the stability of phosphomolybdate, of which upon reduction, it is converted to Mo-blue Glenn & Crane 1956;Sims 1961;Shukor et al 2000). Molybdenum-reducing bacteria isolated previously are also strongly inhibited by phosphate concentration higher than 5 mM Lim et al 2012;Ahmad et al 2013;Halmi et al 2013;Othman et al 2013;AboShakeer et al 2013;Khan et al 2014;.…”

“…Molybdate reduction to Mo-blue in many of the previously isolated Molybdenum-reducing bacteria were inhibited by similar toxic heavy metals Lim et al 2012;Othman et al 2013;. In hexavalent chromate reduction to the trivalent state by Bacillus sp.…”

“…1993;Yunus . 2009;Ahmad et al 2013;Othman et al 2013;Abo-Shakeer et al 2013). The metabolic pathways glycolysis, Kreb's cycle and electron transport chain were used to convert these sugars to NADH and NADPH.…”