RESUMO
A novel pigmented bacterium, initially identified as 11E, was isolated from a site historically known to have various iron-related ores. Phylogenetic analysis of this bacterial strain showed that it belongs to Serratia marcescens. This pigmented S. marcescens 11E cultured individually with glucose, acetate, and glycerol as electron donors along with the soluble electron acceptor iron (Fe) (III) citrate offered a large reduction extent (45.3 %, 31.4 %, and 13.5 %, respectively). On the other hand, when iron oxide (Fe2O3) is used as electron acceptor, the pigmented strain produced a null reduction extent. Surprisingly, the absence of prodigiosin on the bacterial surface (non-pigmented strain) resulted in a large reduction extent of the non-soluble iron form (20-49%). All these extents were comparable and, in some cases, superior to those presented in the literature. Additionally, in the present study, it was found that anthraquinone sulfonate (AQS) stimulated Fe(III) reduction of soluble and non-soluble Fe species only with pigmented S. marcescens. In contrast, in the culture media with the non-pigmented strain, the presence of AQS did not stimulate the Fe(III) reduction. These results suggest that the pigmented phenotype of S. marcescens 11E may perform non-soluble Fe(III) reduction by electron shuttling. In contrast, for the non-pigmented phenotype of this bacterium, non-soluble Fe(III) reduction seems to proceed by direct contact. Our study demonstrates that this bacterium may be used in bioreduction process of heavy metals or as a biocatalyst in bioelectrochemical devices.
Assuntos
Compostos Férricos/metabolismo , Prodigiosina/metabolismo , Serratia marcescens , Enzimas , Filogenia , RNA Ribossômico 16S/genética , Serratia marcescens/genética , Serratia marcescens/isolamento & purificação , Serratia marcescens/metabolismoRESUMO
Seven bacterial strains isolated from a glyphosate-exposed orange plantation site were exposed to 1 mM N-(phosphonomethyl)glycine supplied as a phosphorus source. While some exhibited good biodegradation profiles, the strain 6 P, identified as Bacillus cereus, was the only strain capable of releasing inorganic phosphate to the culture supernatant, while accumulating polyphosphate intracellularly along the experimentation time. The composition and purity of the intracellular polyphosphate accumulated by the strain 6 P were confirmed by FTIR analysis. To date, the biological conversion of glyphosate into polyphosphate has not been reported. However, given the importance of this biopolymer in the survival of microorganisms, it can be expected that this process could represent an important ecological advantage for the adaptation of this strain to an ecological niche exposed to this herbicide. The polyphosphate production yield was calculated as 4 mg l-1, while the glyphosate biodegradation kinetic constant was calculated on 0.003 h-1 using the modified Hockey-Stick first-order kinetic model, with a half-life of 279 h. Our results suggest that B. cereus 6 P is a potential candidate for the generation of an innovative biotechnological process to produce polyphosphate through the biodegradation of the herbicide glyphosate.
Assuntos
Bacillus cereus/metabolismo , Glicina/análogos & derivados , Herbicidas/metabolismo , Bacillus cereus/genética , Bacillus cereus/isolamento & purificação , Biodegradação Ambiental , Glicina/química , Glicina/metabolismo , Herbicidas/química , Cinética , Polifosfatos/química , Polifosfatos/metabolismo , Microbiologia do Solo , GlifosatoRESUMO
There is a current need to develop low-cost strategies to degrade and eliminate industrially used colorants discharged into the environment. Colorants discharged into natural water streams pose various threats, including: toxicity, degradation of aesthetics and inhibiting sunlight penetration into aquatic ecosystems. Dyes and colorants usually have complex aromatic molecular structures, which make them very stable and difficult to degrade and eliminate by conventional water treatment systems. The results in this work demonstrated that heavy metal-resistant Rhodotorula mucilaginosa strain UANL-001L isolated from the northeast region of Mexico produce an exopolysaccharide (EPS), during growth, which has colorant adsorption potential. The EPS produced was purified by precipitation and dialysis and was then physically and chemically characterized by Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and chemical elemental analysis. Here, the ability of the purified EPS produced to adsorb methylene blue (MB), which served as a model colorant, is studied. MB adsorption by the EPS is found to follow Langmuir Adsorption Isotherm kinetics at 25°C. Further, by calculating the Langmuir constant the adsorption capabilities of the EPS produced by the Rhodotorula mucilaginosa strain UANL-001L is compared to that of other adsorbents, both, microbially produced and from agroindustrial waste. The total adsorption capacity of the EPS, from the Rhodotorula mucilaginosa strain UANL-001L, was found to be two-fold greater than the best bioadsorbents reported in the literature. Finally, apart from determining which heavy metals stimulated EPS production in the strain, the optimal conditions of pH, heavy metal concentration, and rate of agitation of the growing culture for EPS production, was determined. The EPS reported here has the potential of aiding in the efficient removal of colorants both in water treatment plants and in situ in natural water streams.
Assuntos
Biomassa , Metais/farmacologia , Polissacarídeos/metabolismo , Rhodotorula/metabolismo , Adsorção , Aerobiose , Concentração de Íons de Hidrogênio , Cinética , México , Testes de Sensibilidade Microbiana , Rhodotorula/isolamento & purificaçãoRESUMO
The effect of pre-treated peat moss on the ability of a sulfate-reducing microbial consortium to remove chromium and lead in solution was evaluated. The most active bacterial community (235.7 mmol H2S/g VSS) was selected from among eight consortia. The peat moss was pre-treated with different HCl concentrations and contact times. The best combination of treatments was 20% HCl for 10 min. The constant substrate affinity Ks was 740 mg COD/L and the ratio COD/SO4(2-) was 0.71. At pH 5, higher production of biogenic sulfide was observed. The up-flowpacked bed bioreactor operated at a flow of 8.3 mL/min for 180 h to obtain removal efficiency (by sulfate-reducing activity) of 90% lead and 65% chromium. It is important to consider that peat moss is a natural adsorbent that further influences the removal efficiency of metal ions.