Microbial Biosorbents Research Articles

Selective biosorption and recovery of Ruthenium from industrial effluents with Rhodopseudomonas palustris strains

This study demonstrated for the first time the possibility to remove and partially recover the Ruthenium contained in industrial effluents by using purple non sulfur bacteria (PNSB) as microbial biosorbents. Up to date, the biosorption was only claimed as possible tool for the removal of the platinum-group metals (PGM) but the biosorption of Ru was never experimentally investigated. The PNSBs tested have adsorbed around 40mgg (dry biomass)(-1) of the Ru contained in the real industrial effluents. At the end of the bioremoval experiments, the amount of Ru recovered from the biomass ranged from 42% to 72% of that adsorbed by PNSB, depending by the characteristics of the Ru effluent used. In any case, the use of microbial sorbents such as PNSB for the biosorption and recovery of Ru can be considered a way to reduce both the costs and the impact on the environment of the mining activities needed to obtain the increasing amounts of this rare and precious metal requested by the industrial activities related to its use.

Bacteria and Fungi as Alternatives for Remediation of Water Resources Polluting Heavy Metals

Classical methods which used for removal of heavy metals from contaminated water are adsorption, precipitation, coagulation, ion exchange resin, evaporation, and membrane processes. Microbial biosorption can be used for the removal of contaminated waters with pollutants such as heavy metals and dyes which are not easily biodegradable. Microbial biosorbents are inexpensive, eco friendly and more effective for the removal of toxic metals from aqueous solution. In this review, the bacterial and fungal abilities for heavy metals ions removal are emphasized. Environmental factors which affect biosorption process are also discussed. A detailed description for the most common isotherm and kinetic models are presented. This article reviews the achievements and the current status of bacterial and fungal biosorption technology for heavy metals removal and provides insights for further researches.

Bioremediation of Chromium from Fortified Solutions by Phanerochaete Chrysosporium (MTCC 787)

Pollution by chromium is of major concern as the metal is used in electroplating, metal finishing leather tanning and chromate preparation. Chromium found in water bodies and in soil is in the form of Cr (III) and Cr (VI). Cr (VI) being of particular concern because of its greater toxicity. At present various microorganisms are used for bioremediation of heavy metals from soil and water bodies. The aim of present work was to bioremediate chromium from fortified solution by a white rot fungus Phanerochaete chrysosporium (MTCC787). The potency of Phanerochaete chrysosporium was evaluated to remediate chromium from fortified solution by viable cells, microbial biosorbents and immobilized cells for the first time. The percentage removal of chromium was analyzed by UV-Visible spectrophotometer (HitachiU-2900). The study shows 99.7% Cr (VI) was removed by biosorption with Phanerochaete chrysosporium detected spectrophotometrically after 72 hrs. This study shows that Phanerochaete chrysosporium is highly potential to be used for the removal of chromium which is also a viable, eco friendly and cost effective technology for cleanup of chromium (VI).

Chemical Modification and Immobilization of Corynebacterium glutamicum for Biosorption of Reactive Black 5 from Aqueous Solution

The main goal of this work was to develop a suitable biosorbent for the remediation of reactive dye bearing wastewaters. The poor mechanical stability of the microbial biosorbent and unfeasible operating conditions often limit the applicability of biosorption to industrial applications. Corynebacterium glutamicum, which has shown a high biosorption capacity under strong acidic conditions, was decarboxylated for the biosorption of Reactive black 5 (RB5) under moderate pH conditions (pH 4). Amine groups were responsible for accommodating the negatively charged RB5 via electrostatic interactions; while the repulsion caused by negatively charged carboxyl groups was minimized via decarboxylation. Isotherm experiments revealed that decarboxylated biomass possessed a maximum uptake of 257.3 mg/g at pH 4, according to the Langmuir model. Immobilization of C. glutamicum using polysulfone matrix enabled the biosorbent to be reused for multiple cycles. Even though immobilized beads showed a tendency to attain slow equilibrium, mainly due to intraparticle diffusion, the efficiency of binding sites was properly utilized. Application of decarboxylated biomass in an up-flow packed column for the continuous biosorption of RB5 was made possible by immobilization and exhibited an uptake of 78.6 mg RB5/g beads. Column regeneration experiments over three cycles revealed that polysulfone-immobilized, decarboxylated C. glutamicum maintained consistently high RB5 uptake, above 74.1 mg/g beads, using 0.01 M NaOH as the elutant.

Predictive modeling of competitive biosorption equilibrium data

This paper compares regression and neural network modeling approaches to predict competitive biosorption equilibrium data. The regression approach is based on the fitting of modified Langmuir-type isotherm models to experimental data. Neural networks, on the other hand, are non-parametric statistical estimators capable of identifying patterns in data and correlations between input and output. Our results show that the neural network approach outperforms traditional regression-based modeling in correlating and predicting the simultaneous uptake of copper and cadmium by a microbial biosorbent. The neural network is capable of accurately predicting unseen data when provided with limited amounts of data for training. Because neural networks are purely data-driven models, they are more suitable for obtaining accurate predictions than for probing the physical nature of the biosorption process.

A high-resolution titrator: a new approach to studying binding sites of microbial biosorbents

The high-resolution potentiometric titration was used as a physico-chemical method to study the acid properties of selected biosorbent materials in order to quantify the functional acidic groups for sorption and to determine their affinities by considering their partial or total ionization equilibrium reactions. The Gran's method and the Henderson-Hasselbach's equation were employed in establishing the partition of the total acidity as associated with strong, weak and very weak acidic chemical active groups. The differences in the total organic acidity (A(TO)) for the two selected types of bacteria and two mycelia revealed by this method were explained by the chemical composition of their cell walls. The total organic acidities obtained were 3.87 me g(-1) for Thiobacillus ferrooxidans, 1.31 me g(-1) for Corynebacterium glutamicum, 0.81 me g(-1) for Aspergillus niger and 2.54 me g(-1) for Rhizopus arrhizus. The links between the activity of protons and the sorption capacities of the selected bioorganic matters were established. Sorption of lead by C. glutamicum and R. arrhizus biomass indicated an optimum pH of 6. It appeared that 64% (Pb(uptake)=0.48 me g(-1)) and 38% (Pb(uptake)=0.28 me g(-1)) of A(TO) were involved during lead sorption onto R. arrhizus and C. glutamicum, respectively. The applications of titration techniques become a powerful tool for the characterization of heterogeneous materials involved in biosorption and bioremediation processes.

Mechanism of metal ion biosorption by fungal biomass

Alkali extracted mycelial biomass from Aspergillus niger, referred to as Biosorb, was found to sequester metal ions (Cd2+, Cu2+, Zn2+, Ni2+ and Co2+) efficiently both from dilute and concentrated solutions upto 10% of its weight (w/w). Sequestration of metal ions from a mixture was also efficient but with attendant antagonisms. The kinetics of metal binding by Biosorb indicated that it is a rapid process and about 70–80% of the metal is removed from solution in 5 min followed by a slower rate. The mechanism of metal binding is shown to be due to exchange of calcium and magnesium ions of the Biosorb during which equimolar concentrations of both the ions were released into the medium. Following this an efficient procedure for the regeneration and reuse of Biosorb was standardized by washing the biosorbent with calcium and magnesium solution (0.1 m). Biosorbents prepared from Neurospora, Fusarium and Penicillium also exhibited similar mechanisms for metal ion binding, though they had a lower metal binding capacity when compared with Biosorb. Chemical modification of carboxylic acid functional groups of the Biosorb resulted in loss of 90% of metal binding capacity which could not be restored even on regeneration. The significance of this finding on the metal sequestration mechanisms of microbial biosorbents is discussed.

Screening of tropical wood-rotting mushrooms for copper biosorption

Fruiting bodies (mushrooms) of nine nonedible macrofungi were screened for copper(II) uptake potential. The maximum uptake potentials (Q(infmax)s) derived from equilibrium studies indicated that all nine species exhibited higher Q(infmax)s at pH 4.0 than that of Filtrasorb-400, a generally used adsorbent for metal removal. Wide variation in Q(infmax) was observed among the species and ranged from 0.048 to 0.383 mmol per g of sorbent. The uptake capacity of Ganoderma lucidum, which exhibited the highest Q(infmax), was higher than those of other microbial biosorbents reported in the literature.