Microbiological Reduction of Molybdenum to Molybdenum Blue as a Sustainable Remediation Tool for Molybdenum: A Comprehensive Review

Abstract

Molybdenum (Mo) microbial bioreduction is a phenomenon that is beginning to be recognized globally as a tool for the remediation of molybdenum toxicity. Molybdenum toxicity continues to be demonstrated in many animal models of spermatogenesis and oogenesis, particularly those of ruminants. The phenomenon has been reported for more than 100 years without a clear understanding of the reduction mechanism, indicating a clear gap in the scientific knowledge. This knowledge is not just fundamentally important—it is specifically important in applications for bioremediation measures and the sustainable recovery of metal from industrial or mine effluent. To date, about 52 molybdenum-reducing bacteria have been isolated globally. An increasing number of reports have also been published regarding the assimilation of other xenobiotics. This phenomenon is likely to be observed in current and future events in which the remediation of xenobiotics requires microorganisms capable of degrading or transforming multi-xenobiotics. This review aimed to comprehensively catalogue all of the characterizations of molybdenum-reducing microorganisms to date and identify future opportunities and improvements.

Molybdate Reduction to Molybdenum Blue and Growth on Polyethylene Glycol by Bacillus sp. strain Neni-8

“…Ghani et al [18] quickly recognize the potential application of this phenomenon for the bioremediation of molybdenum. Since then, numerous Mo-reducing bacteria have been isolated [42]. The ability of the newly isolated Mo-reducing bacterium to grow on other xenobiotics is indeed a highly sought-after property.…”

Immobilization of Bacillus sp. Strain Neni-8 in Dialysis Tubing Reduced Copper Toxicity to the Molybdenum Reduction Process

“…One of them is the enzymatic transformation of metals into precipitable forms in which they pose less risk. Reducing the toxicity of soluble molybdenum can result in the formation of molybdenum blue (Mo-blue), a precipitable substance with a beautiful blue color [23][24][25][26][27][28][29][30][31][32][33].…”

Entrapment of Mo-reducing Bacterium Increase its Resistance towards Mercury

“…The first known instance of molybdenum bioremediation utilizing microorganisms and plants occurred in this region. As a byproduct of copper mining, molybdenum in the form of molybdenite is extracted in Malaysia [14][15][16][17][18][19][20][21][22]. However, there have been several incidents of contamination due to the inadvertent leaking of pipes carrying the metal.…”

“…Enzymatic reduction of metal into a less hazardous precipitable state is one of them. One particularly eye-catching instance is the reduction of molybdenum to molybdenum blue (Mo-blue), a precipitable material with a stunning blue color [3,[20][21][22][23][24][25][26][27][28][29]. It has been known for at least the last century that some microorganisms can convert molybdate into Mo-blue.…”