16 research outputs found
Metal-Induced Production of a Novel Bioadsorbent Exopolysaccharide in a Native Rhodotorula mucilaginosa from the Mexican Northeastern Region
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
Influence of Chloride Salinity on Cadmium uptake by Nicotiana tabacum in a Rhizofiltration System
A hydroponic trial was conducted to study the effect of chloride salinity in simulated effluent on Cd accumulation by tobacco. Leaf surface area (LSA) and root surface area (RSA) measurements were incorporated as possible determinants of Cd uptake rate by plants. Results showed that individual plant differences in Cd content were normalized when including RSA to express Cd uptake rates by plants but not including LSA. A biotic ligand model (BLM) fitted to predict Cd uptake, estimated active and almost linear uptake of the free Cd2+ ion by tobacco plants, while virtually no changes in the chloride complex (CdCl+) uptake were predicted, presumably due to a rapid saturation of the hypothetical root sorption sites at the concentrations used in this trial. Nicotiana tabacum var. K326 is evidenced to be a species potentially suitable for biological wastewater treatment using rhizofiltration at concentrations commonly found in salt-affected wastewater, with high Cd accumulation (185 to 280 mg/kgdm) regardless of water salinity and tolerance up to 80 mmol/L NaCl