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Saeed A.,Environmental Biotechnology Group | Sharif M.,University of Punjab | Iqbal M.,Environmental Biotechnology Group
Journal of Hazardous Materials | Year: 2010

This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation ≥0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16mgg -1. The GFP was regenerated using 1M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions. © 2010 Elsevier B.V. Source

Saeed A.,Environmental Biotechnology Group | Iqbal M.,Environmental Biotechnology Group
Biotechnology Progress | Year: 2013

The review discusses the development of loofa sponge (Luffa cylindrica) as a biotechnological tool and the diversity of applications in which it has been successfully used since it was first reported as a matrix for the immobilization of microbiological cells in 1993. The fibro-vascular reticulated structure, made up of an open network of random lattices of small cross-sections coupled with very high porosity (79-93%), having very low density (0.02-0.04 g/cm3), and high specific pore volume (21-29 cm3/g), has the characteristics of a carrier/scaffold well-suited for cell immobilization. This has been confirmed through the immobilization of cells of diverse types, including filamentous and microalgae, fungi, bacteria, yeasts, higher plants, and human and rat hepatocytes. The cells immobilized in loofa sponge have performed well and better than free suspended cells and those immobilized in conventionally used natural and synthetic polymeric materials for the production of ethanol, organic acids, enzymes, and secondary metabolites. The loofa-immobilized cell systems have been efficiently used for the treatment of wastewaters containing toxic metals, dyes, and chlorinated compounds, and the technology has been used to develop biofilms for the remediation of domestic and industrial wastewaters rich in inorganic and organic matter. In addition, three-dimensional loofa sponge scaffolds for hepatocyte culture have been suggested to have the potential for development into a bioartificial liver device. Loofa sponge is a cost-effective, eco-friendly, and easy to handle matrix that has been used successfully as a biotechnological tool in a variety of systems, purposes, and applications. © 2013 American Institute of Chemical Engineers. Source

Janulevicius A.,Environmental Biotechnology Group | Van Loosdrecht M.C.M.,Environmental Biotechnology Group | Simone A.,Technical University of Delft | Picioreanu C.,Environmental Biotechnology Group
Biophysical Journal | Year: 2010

Myxobacteria are social bacteria that exhibit a complex life cycle culminating in the development of multicellular fruiting bodies. The alignment of rod-shaped myxobacteria cells within populations is crucial for development to proceed. It has been suggested that myxobacteria align due to mechanical interactions between gliding cells and that cell flexibility facilitates reorientation of cells upon mechanical contact. However, these suggestions have not been based on experimental or theoretical evidence. Here we created a computational mass-spring model of a flexible rod-shaped cell that glides on a substratum periodically reversing direction. The model was formulated in terms of experimentally measurable mechanical parameters, such as engine force, bending stiffness, and drag coefficient. We investigated how cell flexibility and motility engine type affected the pattern of cell gliding and the alignment of a population of 500 mechanically interacting cells. It was found that a flexible cell powered by engine force at the rear of the cell, as suggested by the slime extrusion hypothesis for myxobacteria motility engine, would not be able to glide in the direction of its long axis. A population of rigid reversing cells could indeed align due to mechanical interactions between cells, but cell flexibility impaired the alignment. © 2010 by the Biophysical Society. Source

Ayra-Pardo C.,Environmental Biotechnology Group | Raymond B.,Imperial College London | Gulzar A.,Imperial College London | Gulzar A.,Pmas Arid Agriculture University | And 4 more authors.
Insect Molecular Biology | Year: 2015

The widespread and sustainable exploitation of the entomopathogen Bacillus thuringiensis (Bt) in pest control is threatened by the evolution of resistance. Although resistance is often associated with loss of binding of the Bt toxins to the insect midgut cells, other factors have been implicated. Here we used suppressive subtractive hybridization and gene expression suppression to identify additional molecular components involved in Bt-resistance in Plutella xylostella. We isolated transcripts from genes that were differentially expressed in the midgut of larvae from a resistant population, following ingestion of a Bt kurstaki HD1 strain-based commercial formulation (DiPel), and compared with a genetically similar susceptible population. Quantitative real-time polymerase-chain reaction (RT-PCR) analysis confirmed the differential basal expression of a subset of these genes. Gene expression suppression of three of these genes (P. xylostella cyclin-dependent kinase 5 regulatory subunit associated protein 1-like 1, stromal cell-derived factor 2-like 1 and hatching enzyme-like 1) significantly increased the pathogenicity of HD1 to the resistant population. In an attempt to link the multitude of factors reportedly influencing resistance to Bt with the well-characterized loss of toxin binding, we also considered Bt-resistance models in P. xylostella and other insects. © 2015 The Royal Entomological Society. Source

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