Magnetic separation of algae genetically modified for increased intracellular iron uptake

Review on rewiring of microalgal strategies for the heavy metal remediation - A metal specific logistics and tactics

Phycoremediation of heavy metals are gaining much attention and becoming an emerging practice for the metal removal in diverse environmental matrices. Still, the physicochemical state of metal polluted sites is often found to be complex and haphazard in nature due to the irregular discharge of wastes, that leads to the lack of conjecture on the application of microalgae for the metal bioremediation. Besides, the foresaid issues might be eventually ended up with futile effect to the polluted site. Therefore, this review is mainly focusing on interpretative assessment on pre-existing microalgal strategies and their merits and demerits for selected metal removal by microalgae through various process such as natural attenuation, nutritional amendment, chemical pretreatment, metal specific modification, immobilization and amalgamation, customization of genetic elements and integrative remediation approaches. Thus, this review provides the ideal knowledge for choosing an efficient metal remediation tactics based on the state of polluted environment. Also, this in-depth description would provide the speculative knowledge of counteractive action required for pass-over the barriers and obstacles during implementation. In addition, the most common metal removal mechanism of microalgae by adsorption was comparatively investigated with different metals through the principal component analysis by grouping various factor such as pH, temperature, initial metal concentration, adsorption capacity, removal efficiency, contact time in different microalgae. Conclusively, the suitable strategies for different heavy metals removal and addressing the complications along with their solution is comprehensively deliberated for metal removal mechanism in microalgae.

Engineered microbes as effective tools for the remediation of polyaromatic aromatic hydrocarbons and heavy metals

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) have become a major concern to human health and the environment due to rapid industrialization and urbanization. Traditional treatment measures for removing toxic substances from the environment have largely failed, and thus development and advancement in newer remediation techniques are of utmost importance. Rising environmental pollution with HMs and PAHs prompted the research on microbes and the development of genetically engineered microbes (GEMs) for reducing pollution via the bioremediation process. The enzymes produced from a variety of microbes can effectively treat a range of pollutants, but evolutionary trends revealed that various emerging pollutants are resistant to microbial or enzymatic degradation. Naturally, existing microbes can be engineered using various techniques including, gene engineering, directed evolution, protein engineering, media engineering, strain engineering, cell wall modifications, rationale hybrid design, and encapsulation or immobilization process. The immobilization of microbes and enzymes using a variety of nanomaterials, membranes, and supports with high specificity toward the emerging pollutants is also an effective strategy to capture and treat the pollutants. The current review focuses on successful bioremediation techniques and approaches that make use of GEMs or engineered enzymes. Such engineered microbes are more potent than natural strains and have greater degradative capacities, as well as rapid adaptation to various pollutants as substrates or co-metabolizers. The future for the implementation of genetic engineering to produce such organisms for the benefit of the environment andpublic health is indeed long and valuable.

Biological approaches practised using genetically engineered microbes for a sustainable environment: A review

Conventional methods used to remediate toxic substances from the environment have failed drastically, and thereby, advancement in newer remediation techniques can be one of the ways to improve the quality of bioremediation. The increased environmental pollution led to the exploration of microorganisms and construction of genetically engineered microbes (GEMs) for pollution abatement through bioremediation. The present review deals with the successful bioremediation techniques and approaches practised using genetically modified or engineered microbes. In the present scenario, physical and chemical strategies have been practised for the remediation of domestic and industrial wastes but these techniques are expensive and toxic to the environment. Involving engineered microbes can provide a much safer and cost effective strategy in comparison with the other techniques. With the aid of biotechnology and genetic engineering, GEMs are designed by transforming microbes with a more potent protein to overexpress the desired character. GEMs such as bacteria, fungi and algae have been used to degrade oil spills, camphor, hexane, naphthalene, toluene, octane, xylene, halobenzoates, trichloroethylene etc. These engineered microbes are more potent than the natural strains and have higher degradative capacities with quick adaptation for various pollutants as substrates or cometabolize. The road ahead for the implementation of genetic engineering to produce such organisms for the welfare of the environment and finally, public health is indeed long and worthwhile.

Intrinsically Magnetic Cells: A Review on Their Natural Occurrence and Synthetic Generation

The magnetization of non-magnetic cells has great potential to aid various processes in medicine, but also in bioprocess engineering. Current approaches to magnetize cells with magnetic nanoparticles (MNPs) require cellular uptake or adsorption through in vitro manipulation of cells. A relatively new field of research is "magnetogenetics" which focuses on in vivo production and accumulation of magnetic material. Natural intrinsically magnetic cells (IMCs) produce intracellular, MNPs, and are called magnetotactic bacteria (MTB). In recent years, researchers have unraveled function and structure of numerous proteins from MTB. Furthermore, protein engineering studies on such MTB proteins and other potentially magnetic proteins, like ferritins, highlight that in vivo magnetization of non-magnetic hosts is a thriving field of research. This review summarizes current knowledge on recombinant IMC generation and highlights future steps that can be taken to succeed in transforming non-magnetic cells to IMCs.

Single cell magnetometry by magnetophoresis vs. bulk cell suspension magnetometry by SQUID-MPMS - a comparison

Paramagnetic constituents of a cell have strong effect on cell's volume magnetic susceptibility even at low volume fraction because of their high susceptibility relative to that of the diamagnetic cell constituents. The effect can be measured at a single cell level by measuring cell terminal velocity in viscous media using a microscope equipped with a well-defined field and gradient magnet configuration (referred to as magnetophoretic analysis by cell tracking velocimetry, CTV). The sensitivity of such a microscopic-scale magnetometry was compared to that of a reference method of superconducting quantum interference-magnetic properties measurement system (SQUID-MPMS) using a red blood cell (RBC) suspension model. The RBC hemoglobin oxygen saturation determines the hemoglobin molecular magnetic susceptibility (diamagnetic when fully oxygenated, paramagnetic when fully deoxygenated or converted to methemoglobin). The SQUID-MPMS measurements were performed on an average of 5,000 RBCs in 20 μL physiological phosphate buffer at room temperature, those by CTV on a single cell track in a mean magnetic field of 1.6 T and mean gradient of 240 T/m, repeated for an average of 1,000 tracks per sample. This suggests 5,000× higher sensitivity of cell susceptometry by magnetophoretic analysis than by SQUID-MPMS. The magnetophoretic mean RBC magnetic susceptibilities were in the range determined by SQUID-MPMS (lower limit) and theory (upper limit). The ability of magnetophoretic analysis to resolve susceptibility peaks in a mixed cell populations was confirmed for an oxy RBC and met RBC mixture. Magnetophoretic analysis by CTV provides new tool for studies of emergence of paramagnetic reaction products in the cell.