Bioreduction potential of Providencia sp. and microbial consortium for hexavalent molybdenum: Isolation, identification, characterization, and optimization by response surface methodology

Molybdenum, a heavy metal with industrial applications, poses global toxicity concerns at concentrations exceeding 0.07 mg/L. This study aimed to isolate, characterize and optimize the molybdenum (Mo) reduction potential of bacterial strain and a mixed consortia. We used low phosphate media (LPM) for the isolation and optimization, employing one-factor-at-a-time (OFAT) and Response Surface Methodology (RSM) approaches. Molecular identification based on 16S ribosomal RNA sequencing of the Mo-reducing bacterial isolate revealed Providencia sp. Optimization via OFAT showed that this isolate effectively reduced 60 mM molybdate with optimal conditions of 2 mM phosphate and 10 mM fructose. The mixed consortium achieved remarkable reduction of molybdate at concentration up to 100 mM, the highest reported concentration to date. The RSM optimization of Providencia sp. revealed that the best reduction was supported by a pH of 6.50 and 60 mM molybdate. However, RSM was not successful with the consortium using the Plackett-Burman Design, suggesting that alternative designs should be explored for future optimization. This study advances understanding of Mo-reduction and highlights significant achievements in handling high molybdate concentrations.