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

Abstract

Molybdenum is an emerging pollutant worldwide. The objective of this study is to isolate molybdenum-reducing bacterium with the ability to grow on phenolic compounds (phenol and catechol). The screening process was carried out on a microplate. The bacterium reduced molybdenum in the form of sodium molybdate to molybdenum blue (Mo-blue). The bacterium required a narrow pH range for optimal reduction of molybdenum, i.e. between pH 6.3 and o 6.8, with temperature between 34 and 37 C. Molybdate reduction to Mo-blue was best supported by glucose as the carbon source. However, both phenol and catechol could not support molybdate reduction. Other requirements for molybdate reduction included sodium molybdate concentrations between 15 and 30 mM, and phosphate concentration of 5.0 mM. The bacterium exhibited a Mo-blue absorption spectrum with a shoulder at 700 nm and a maximum peak near the infrared region at 865 nm. The Mo-reducing bacterium was partially identified as Enterobacter sp. strain Saw-2. The capability of this bacterium to grow on toxic phenolic compounds and to detoxify molybdenum made it a significant agent for bioremediation.

Optimisation of Various Physicochemical Variables Affecting Molybdenum Bioremediation Using Antarctic Bacterium, Arthrobacter sp. Strain AQ5-05

“…The preferability of simple sugars such as glucose and sucrose in Mo reduction m also be because Mo reduction is growth-associated; therefore, the use of easily assimi sugar is more favourable [6]. In comparison with a study by Ahmad et al [7] using domonas sp. strain DRY1 isolated from Antarctic soil, glucose was the best electron d while Darham et al [17] reported that Mo-reducing Antarctic marine bacterium Ma monas sp.…”

“…Ahmad et al [8] stated that (NH 4 ) 2 SO 4 is an easily assimilable nitrogen source along with two ammonium ions to be used. Furthermore, its availability to be commonly utilised by bacteria and affordable for practical bioremediation have made (NH 4 ) 2 SO 4 a good nitrogen source [7]. Previous work on Marinomonas sp.…”

“…However, bioremediation is a more effective method for polluted land and water and is more ecologically sustainable [6]. Bioremediation of Mo involves a complex enzymatic reduction process by reducing sodium molybdate (6+) to Mo-blue, a colloid with oxidation states of 5+ [7,8]. In 37 2− , which can be reduced by reducing agents or combined with many heteroatoms such as phosphate [10].…”

“…Subsequently, a series of different concentra of (NH4)2SO4 ranging from 0.1 to 0.6 g/L were assessed to find the optimum concentra Figure3bindicates that the optimum Mo reduction and the highest bacterial growth observed at 0.3 g/L.Ahmad et al[8] stated that (NH4)2SO4 is an easily assimilable nitrogen source a with two ammonium ions to be used. Furthermore, its availability to be commonly lised by bacteria and affordable for practical bioremediation have made (NH4)2SO4 a nitrogen source[7]. Previous work on Marinomonas sp.…”

Yield coefficient for the growth of Pseudomonas sp. AQ5-04 at various concentrations of phenol

“…In Malaysia, the National Guidelines for Drinking Water Quality Standard is 0.002 mg/L and the 2014 Environmental Quality Report demonstrated that nearly all of the groundwater observing stations had exceeded this level for phenol. This is due to phenol and phenolic substances are the number one scheduled waste product in Malaysia as their usage in the industrial sector is one of the highest (Ahmad et al, 2011a(Ahmad et al, , 2012(Ahmad et al, , 2017Arif et al, 2013;Department of Environmental, 2014;Gami et al, 2014b;AbdEl-Mongy et al, 2015;Norazah et al, 2015;Sabullah et al, 2017).…”