Remarkably high Pb2+ binding capacity of a novel, regenerable bioremediator Papiliotrema laurentii RY1: Functional in both alkaline and neutral environments.

The ability of P. laurentii strain RY1 to remediate lead (Pb2+) from water was investigated in batch and column studies. The lead removal ability of non-viable biomass, non-viable biomass immobilised on agar-agar (biobeads) and agar-agar at different pH was compared in batch studies. It was found that among the three, biobeads have maximum ability to remove Pb2+ followed by biomass and agar-agar beads. Maximum and almost equal lead removal by biobeads was observed at both neutral and alkaline pH making it a novel and more applicable bioremediator as all other reported bioremediators have a single pH for optimum activity. Studies were performed to determine the optimum conditions for lead removal from aqueous solutions for biobeads. The physical and chemical characterization of the biobeads before and after Pb2+ biosorption was done by using S.E.M. and F.T.I.R. respectively. The adsorption of Pb2+ on biobeads obeyed the Langmuir adsorption isotherm and pseudo first order kinetics. These mean that the Pb2+ binding sites are identical, located on the surface of the adsorbant and the rate of Pb2+ removal from aqueous solution is directly proportional to the number of Pb2+ binding sites on the biobeads. The thermodynamics of the biosorption process is also investigated. The binding capacity of the biobeads in batch study was found to be 52.91mg/gm which is higher in comparison to other reported yeast bioremediators. The used biobeads can be desorbed using 0.1(M) CaCl2. The desorbed biobeads can be used subsequently for several cycles of lead removal making it cost-effective. Column studies were also performed for biobeads with the help of Thomas model for examining its suitability for industrial application. Maximum specific lead uptake of the biobeads when applied in the column was found to be 58.26mg/gm which being promising makes it suitable for application in industries involved in the treatment of wastewater contaminated with high amounts of lead. The high mass transfer co-efficient indicate that small sized column can be used effectively to remove high amounts of lead which makes the bioremediation process by the biobeads more economical and advantageous for industrial application. Several factors like effectiveness of the biobeads in Pb2+removal at both neutral and alkaline pH, reusability, high mass transfer co-efficient, regenerability and high binding capacity makes it a novel versatile, cost-effective and high utility bioremediator.

Removal of Pb (II), As (III), and Cr (VI) by nitrogen-starved Papiliotrema laurentii strain RY1.

Heavy metals such as lead, chromium, and metalloid like arsenic dominate the pinnacle in posing a threat to life. Being environment-friendly, elucidating the mechanism by which microorganisms detoxify such elements has always been an active field of research hitherto. In the present study, we have investigated the capability of nitrogen-deprived Papiliotrema laurentii strain RY1 toward enhanced tolerance and neutralizing toxic elements. There were biosorption and bioprecipitation of lead and chromium at the cell surfaces. Bioprecipitation mechanisms included the formation of lead phosphates and pyromorphites from lead, grimaldite from chromium. Transcripts such as metallothionein, aquaporins, and arsenical pump-driving ATPase have been surmised to be involved in the detoxification of elements. Furthermore, activation of antioxidant defense mechanisms for the cells for each of the elements should contribute towards yeast's propagation. The efficiency of removal of elements for live cells and immobilized cells were high for lead and chromium. To the best of our knowledge, this is the first report of such high tolerance of lead, arsenic, and chromium for any yeast. The yeast showed such varied response under dual stress due to nitrogen starvation and in the presence of respective elements. The yeast possesses promising potentials in nitrogen deprived and enriched environments to aid in bioremediation sectors.

Assessment on the decolourization of textile dye (Reactive Yellow) using Pseudomonas sp. immobilized on fly ash: Response surface methodology optimization and toxicity evaluation.

This study focuses on the investigation of removal of textile dye (Reactive Yellow) by a combined approach of sorption integrated with biodegradation using low cost adsorbent fly ash immobilized with Pseudomonas sp. To ensure immobilization of bacterial species on treated fly ash, fly ash with immobilized bacterial cells was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and fluorescence microscopy. Comparative batch studies were carried out using Pseudomonas sp, fly ash and immobilized Pseudomonas sp on flyash and were observed that immobilized Pseudomonas sp on flyash acted as better decolourizing agent. The optimized pH, temperature, and immobilized adsorbent dosage for highest percentage of dye removal were observed to be pH 6, 303 K, 1.2 g/L in all the cases. At optimum condition, the highest percentage of dye removal was found to be 88.51%, 92.62% and 98.72% for sorption (flyash), biodegradation (Pseudomonas sp) and integral approach (Pseudomonas sp on flyash) respectively. Optimization of operating parameters of textile dye decolourization was done by response surface methodology (RSM) using Design Expert 7 software. Phytotoxicity evaluation with Cicer arietinum revealed that seeds exposed to untreated dye effluents showed considerably lower growth, inhibited biochemical, and enzyme parameters with compared to those exposed to treated textile effluents. Thus this immobilized inexpensive technique could be used for removal of synthetic dyes present in textile wastewater.

Coconut coir-derived nanocellulose as an efficient adsorbent for removal of cationic dye safranin-O: a detailed mechanistic adsorption study.

Coconut (Cocos nucifera) coir is an abundant agricultural waste prevalent worldwide. Utilization of this waste has been carried out in this study by obtaining nanocellulose (NC) fibres for wastewater remediation purposes. Nanocellulose was obtained from coconut coir using bleaching and acid-alkali treatments followed by ultrasonication and lyophilization. The structural, compositional, surface and thermal properties of the synthesized material were identified using transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption/desorption, differential thermal (DT) and derivative thermogravimetric (DTG) analyses. These analyses confirmed the synthesized NC with enhanced thermal stability and porosity which was further used for adsorption process. After synthesis, NC was used for the removal of cationic dye safranin-O from water under ambient conditions through batch adsorption studies. The batch adsorption studies revealed that at 10 ppm of dye concentration, above 99% removal was achieved by 100 mg dosage of NC within 4.5 h at room temperature with qe (maximum adsorption capacity at equilibrium) value of around 83 mg g-1. The corresponding adsorption process fitted well with Langmuir isotherm and pseudo-second order kinetics. The primary mode of adsorption from the thermodynamic studies was found to be chemisorption. The adsorption process was achieved through response surface methodology (RSM) study which revealed that at optimized conditions of temperature 35 °C with a dose of 137.50 mg and contact time of 180 min, above 99% of dye (conc. 0.01 mg mL-1) was removed. In addition, the adsorbent can be recycled up to six cycles without any significant loss of its adsorption capacity. The present comprehensive study revealed that a greener eco-friendly synthesis of NC from waste material coconut coir was an effective nanoadsorbent for dye removal with high efficacy. This surely opens up opportunities to develop sustainable protocols for efficient environmental remediation.

Integral approach of sorption coupled with biodegradation for treatment of azo dye using Pseudomonas sp.: batch, toxicity, and artificial neural network.

The present study investigated the removal of azo dye (crystal violet) by adsorption (using a low-cost adsorbent fly ash), biodegradation (using bacterial species, Pseudomonas sp.), and an integrated approach of sorption coupled with biodegradation (using fly ash immobilized with Pseudomonas sp.) on a comparative scale. To ascertain immobilization of bacteria on fly ash, immobilized bacterial cells were characterized by energy-dispersive X-ray spectroscopy, scanning electron microscopy, Fourier-transform-infrared spectroscopy, and fluorescence microscopy. Batch studies were conducted for optimization of the process parameters for ensuring maximum dye removal. The optimum pH, temperature, and initial dye concentration for the highest percentage of dye removal were found to be pH 7, 37 °C, and 50 mg/L in all the three cases. Under optimized conditions, the highest percentage of dye removal was found to be 89.24, 79.64, and 99.04% for biodegradation, sorption, and integrated approach of sorption and biodegradation, respectively. Finally, phytotoxicity studies carried out with the treated water on Cicer arietinum seeds also carried proved that these processes and the adsorbent did not exert any toxic effects on the seeds. Artificial neural network modeling revealed a close interaction between theoretically predicted and experimentally obtained results and with an error of around 1.1%. Thus, this novel, environmentally sustainable and economically viable technique may be applied for effective removal of crystal violet from industrial wastewater.