Bacterial Reduction of Cr(VI) and Fe(III) in In Vitro Conditions

Abstract

Chemical reduction of Cr(VI) can be a strategy to detoxify toxic metals in oxidized states, whereas reduction of Fe(III) could enhance the availability of Fe in the form of Fe(II) to boost plant growth. However, it creates another problem of chemical sludge disposal. Hence, microbial conversion of Cr(VI) to Cr(III) and Fe(III) to Fe(II) is preferred over the chemical method. Out of 11 bacterial strains isolated from the rhizospheric zone of Typha latifolia growing on fly ash dump sites, four isolates were selected for the reduction of Cr(VI) and Fe(III) and were identified as Micrococcus roseus NBRFT2 (MTCC 9018), Bacillus endophyticus NBRFT4 (MTCC 9021), Paenibacillus macerans NBRFT5 (MTCC 8912), and Bacillus pumilus NBRFT9 (MTCC 8913). These strains were individually tested for survival at different concentrations of Cr(VI) and Fe(III), pH, and temperature, and then, their ability for reduction of both metals was evaluated at optimum pH 8.0 and temperature 35 C. The results indicated that NBRFT5 was able to reduce the maximum amount, 99% Cr(VI) and 98% Fe(III). Other strains also reduced these metals to different levels, but less than NBRFT5. Hence, these strains may be used for decontamination of metal-contaminated sites, particularly with Cr(VI) and Fe(III) through the reduction process.

Tolerance and reduction of Cr(VI) by Bacillus amyloliquefaciens, B. thuringiensis and Paenibacillus sp., isolated from Pasto River

“…The results obtained in this research coincide with studies that affirm that bacteria belonging to the genus Paenibacillus have the ability to reduce hexavalent chromium, in our case 86.4% in 84 h from an initial concentration of 100 mg / L. Paenibacillus xylaniliticus on the other hand, it showed the capacity to reduce approximately 80.43% of chromium, after an initial concentration of 19.7 mg / L at 72 h (Molokwane, et al, 2008;Rawat, et al, 2013). However, these percentages could be maximized when modifying other parameters such as temperature and pH as demonstrated by Tiwari et al, (2014) in their process determined that the Cr(VI) reductions of Paenibacillus macerans are 99% efficient at 35 ° C and pH 8 (Tiwari, et al, 2014). Similarly, the ability of B. thuringiensis to carry out the reduction process has been previously reported.…”

Eficiencia en la reducción de Cromo por una bacteria silvestre en un tratamiento tipo Batch utilizando como sustrato agua residual del municipio de Pasto, Colombia

“…En cuanto a Paenibacillus sp., varios autores describen que bacterias pertenecientes a este género como, P. xylaniliticus presentan la capacidad de reducir aproximadamente el 80,43% de Cromo, en una concentración inicial de 19,7 mg/L después de 72 h 30 . Tiwari et al, evidenciaron la reducción de Cr (VI) de P. macerans, con una eficiencia del 99% a 35 °C y pH 8,0 31 . Al respecto, se reporta que el género Paenibacillus tiene la capacidad de secretar polímeros extracelulares como, polisacáridos que incrementan la afinidad con metales pesados, un caso relacionado fue descrito por Shiomi 32 en el que P. jamilae presenta un aumento en la afinidad por Plomo atribuida a los polisacáridos que secreta.…”

Genomic analysis of a ginger pathogen Bacillus pumilus providing the understanding to the pathogenesis and the novel control strategy

“…Based on its abilities in producing vanillin, keratinase, xylanase, alkaline serine protease and several other bioactive substances 2 3 4 5 , B. pumilu s is widely used in industrial processes, such as the production of several traditional fermented foods, the treatment of wastewater and the degradation of environmental pollutants 6 7 . More recently, B. pumilus found in healthy plant tissue was reported with properties in promoting plant growth by enhancing the uptake of nutrients, nitrogen fixation, interaction with symbiotic microorganisms and producing antimicrobial agents against pathogenic bacteria and fungi as well as by reducing metal toxicity 8 9 10 11 . According to previous reports, several other B. pumilus strains are also used as probiotics for animals 12 .…”