Bio-nanotechnology application in wastewater treatment

The nanoparticles have received high interest in the field of medicine and water purification, however, the nanomaterials produced by chemical and physical methods are considered hazardous, expensive, and leave behind harmful substances to the environment. This chapter aimed to focus on green-synthesized nanoparticles and their medical applications. Moreover, the chapter highlighted the applicability of the metallic nanoparticles (MNPs) in the inactivation of microbial cells due to their high surface and small particle size. Modifying nanomaterials produced by green-methods is safe, inexpensive, and easy. Therefore, the control and modification of nanoparticles and their properties were also discussed

Biodesalination: A Case Study for Applications of Photosynthetic Bacteria in Water Treatment

Shortage of freshwater is a serious problem in many regions worldwide, and is expected to become even more urgent over the next decades as a result of increased demand for food production and adverse effects of climate change. Vast water resources in the oceans can only be tapped into if sustainable, energy-efficient technologies for desalination are developed. Energization of desalination by sunlight through photosynthetic organisms offers a potential opportunity to exploit biological processes for this purpose. Cyanobacterial cultures in particular can generate a large biomass in brackish and seawater, thereby forming a low-salt reservoir within the saline water. The latter could be used as an ion exchanger through manipulation of transport proteins in the cell membrane. In this article, we use the example of biodesalination as a vehicle to review the availability of tools and methods for the exploitation of cyanobacteria in water biotechnology. Issues discussed relate to strain selection, environmental factors, genetic manipulation, ion transport, cell-water separation, process design, safety, and public acceptance

Bioaccumulation of gold by sulfate-reducing bacteria cultured in the presence of gold(I)-thio sulfate complex

A sulfate-reducing bacterial (SRB) enrichment, from the Driefontein Consolidated Gold Mine, Witwatersrand Basin, Republic of South Africa, was able to destabilize gold(I)-thiosulfate complex (Au (S O) ) and precipitate elemental gold. The precipitation of gold was observed in the presence of active (live) SRB due to the formation and release of hydrogen sulfide as an end-product of metabolism, and occurred by three possible mechanisms involving iron sulfide, localized reducing conditions, and metabolism. The presence of biogenic iron sulfide caused significant removal of gold from solutions by adsorption and reduction processes on the iron sulfide surfaces. The presence of gold nanoparticles within and immediately surrounding the bacterial cell envelope highlights the presence of localized reducing conditions produced by the bacterial electron transport chain via energy generating reactions within the cell. Specifically, the decrease in redox conditions caused by the release of hydrogen sulfide from the bacterial cells destabilized the Au (S O) solutions. The presence of gold as nanoparticles

Morphology of gold nanoparticles synthesized by filamentous cyanobacteria from gold(I)-thiosulfate and gold(III)-chloride complexes

Plectonema boryanum UTEX 485, a filamentous cyanobacterium, has been reacted with aqueous Au(SO) and AuCl solutions (∼400-550 mg/L Au) at 25-100°C for up to 1 month and at 200°C for 1 day. The interaction of cyanobacteria with aqueous Au(SO) promoted the precipitation of cubic (100) gold nanoparticles (< 10-25 nm) at membrane vesicles and admixed with gold sulfide within cells and encrusted on the cyanobacteria, whereas reaction with AuCl resulted in the precipitation of octahedral (111) gold platelets (∼1-10 μm) in solutions and nanoparticles of gold (< 10 nm) within bacterial cells. Functional groups imaged by negative ion TOP- SIMS on (111) faces of the octahedral platelets were predominantly Cl and CN. with smaller amounts of CH and CNO

Synthesis of platinum nanoparticles by reaction of filamentous cyanobacteria with platinum(IV)-chloride complex

Interaction of cyanobacteria (Plectonema boryanum UTEX 485) with aqueous platinum(IV)-chloride (PtCl°) has been investigated at 25-100°C for up to 28 days, and 180°C for 1 day. The addition of PtCl° to the cyanobacteria culture initially promoted the precipitation of Pt(II)-organic material as amorphous spherical nanoparticles (≤0.3 μm) in solutions and dispersed nanoparticles within bacterial cells. The spherical Pt(II)-organic nanoparticles were connected into long beadlike chains by a continuous coating of organic material derived from the cyanobacterial cells, and aged to nanoparticles of crystalline platinum metal with increase in temperature and reaction time. The stepwise reduction for the formation of platinum nanoparticles in the presence of cyanobacteria was deduced to be Pt(IV) [PtCl°] → Pt(II) [Pt(II) - organics] → Pt(0). Spherical platinum-bearing nanoparticles were not present in abiotic PtCl° experiments conducted under similar conditions and duration