Nanoengineering TiO2 for evaluating performance in dye sensitized solar cells with natural dyes.

The current study employs nanoengineering diatom and TiO2 NPs to form diatom-Si-TiO2 nanoengineered structures to fabricate a dye sensitized solar cell (DSSC) (DsTnas-DSSC). This was characterized and spin coated on a Fluorine-doped Tin Oxide (FTO) anode plate. The counter cathode was prepared by spin coating graphene oxide on a FTO glass plate and using Lugol's iodine as an electrolyte. The power density of DsTnas-DSSC was estimated with different natural dyes in comparison to conventional photosensitive ruthenium dye. It was found that the natural dyes extracted from plants and microalgae show significant power efficiencies in DSSC. The percentage efficiency of maximum power densities (PDmax) of DsTnas-DSSC obtained with photosensitive dyes were 9.4% with synthetic ruthenium dye (control) and 7.19% > 4.08% > 0.72% > 0.58% > 0.061% from natural dyes found in Haematococcus pluvialis (astaxanthin) > Syzygium cumini (anthocyanin) > Rosa indica (anthocyanin) > Hibiscus rosa-sinensis (anthocyanin) > Beta vulgaris (betalains), respectively. Among all the natural dyes used, the PDmax for the control ruthenium dye was 6.164 mW m-2 followed by the highest in astaxanthin natural dye from Haematococcus pluvialis (5.872 mW m-2). Overall, the use of natural dye DsTnas-DSSC makes the fuel cell low cost and an alternative to conventional expensive, metal and synthetic dyes.

Strategies and challenges to enhance commercial viability of algal biorefineries for biofuel production.

The rise in energy consumption would quadruple in the coming century and the, existing energy resources might be insufficient to meet the demand of the growing population. An alternative and sustainable energy resource is therefore needed to address the fossil fuel deficiency. The utility of microalgae strains in the aspect of biorefinery has been in research for quite some time. Algal biorefinery is an alternate way of renewable energy however even after decades of research it still suffers from commercialization bottlenecks. The current manuscript reviews the scenarios where the innovation needs an ignition for its commercialization. This review discusses the prospects of up-scale cultivation, and harvesting algal biomass for biorefineries. It narrates algal biorefinery hurdles that can be solved using integrated technology approach, life cycle assessment and applications of nanotechnology. The review also sheds light upon the ties of algal biorefineries with its economic viability.

Astaxanthin as a King of Ketocarotenoids: Structure, Synthesis, Accumulation, Bioavailability and Antioxidant Properties.

Astaxanthin (3,3-dihydroxy-ß, ß-carotene-4,4-dione) is a ketocarotenoid synthesized by Haematococcus pluvialis/lacustris, Chromochloris zofingiensis, Chlorococcum, Bracteacoccus aggregatus, Coelastrella rubescence, Phaffia rhodozyma, some bacteria (Paracoccus carotinifaciens), yeasts, and lobsters, among others However, it is majorly synthesized by Haematococcus lacustris alone (about 4%). The richness of natural astaxanthin over synthetic astaxanthin has drawn the attention of industrialists to cultivate and extract it via two stage cultivation process. However, the cultivation in photobioreactors is expensive, and converting it in soluble form so that it can be easily assimilated by our digestive system requires downstream processing techniques which are not cost-effective. This has made the cost of astaxanthin expensive, prompting pharmaceutical and nutraceutical companies to switch over to synthetic astaxanthin. This review discusses the chemical character of astaxanthin, more inexpensive cultivating techniques, and its bioavailability. Additionally, the antioxidant character of this microalgal product against many diseases is discussed, which can make this natural compound an excellent drug to minimize inflammation and its consequences.

Sustainable treatment of dye wastewater by recycling microalgal and diatom biogenic materials: Biorefinery perspectives.

Discharge of untreated or partially treated toxic dyes containing wastewater from textile industries into water streams is hazardous for environment. The use of heavy metal(s) rich dyes, which are chemically active in azo and sulfur content(s) has been tremendously increasing in last two decades. Conventional physical and chemical treatment processes help to eliminate the dyes from textile wastewater but generates the secondary pollutants which create an additional environmental problem. Microalgae especially the diatoms are promising candidate for dye remediation from textile wastewater. Nanoporous diatoms frustules doped with nanocomposites increase the wastewater remediation efficiency due to their adsorption properties. On the other hand, microalgae with photosynthetic microbial fuel cell have shown significant results in being efficient, cost effective and suitable for large scale phycoremediation. This integrated system has also capability to enhance lipid and carotenoids biosynthesis in microalgae while simultaneously generating the bioelectricity. The present review highlights the textile industry wastewater treatment by live and dead diatoms as well as microalgae such as Chlorella, Scenedesmus, Desmodesmus sp. etc. This review engrosses applicability of diatoms and microalgae as an alternative way of conventional dye removal techniques with techno-economic aspects.

A techno-economic approach for eliminating dye pollutants from industrial effluent employing microalgae through microbial fuel cells: Barriers and perspectives.

Microbial fuel cells are biochemical factories which besides recycling wastewater are electricity generators, if their low power density can be scaled up. This also adds up to work on many factors responsible to increase the cost of running a microbial fuel cell. As a result, the first step is to use environment friendly dead organic algae biomass or even living algae cells in a microbial fuel cell, also referred to as microalgal microbial fuel cells. This can be a techno-economic aspect not only for treating textile wastewater but also an economical way of obtaining value added products and bioelectricity from microalgae. Besides treating wastewater, microalgae in its either form plays an essential role in treating dyes present in wastewater which essentially include azo dyes rich in synthetic ions and heavy metals. Microalgae require these metals as part of their metabolism and hence consume them throughout the integration process in a microbial fuel cell. In this review a detail plan is laid to discuss the treatment of industrial effluents (rich in toxic dyes) employing microbial fuel cells. Efforts have been made by researchers to treat dyes using microbial fuel cell alone or in combination with catalysts, nanomaterials and microalgae have also been included. This review therefore discusses impact of microbial fuel cells in treating wastewater rich in textile dyes its limitations and future aspects.

Microalgal drugs: A promising therapeutic reserve for the future.

Over the decades, a variety of chemically synthesized drugs are being used to cure existing diseases but often these drugs could not be effectively employed for the treatment of serious and newly emerging diseases. Fortunately, in nature there occurs immense treasure of plants and microorganisms which are living jewels with respect to their richness of medically important metabolites of high value. Hence, amongst the existing microorganism(s), the marine world offers a plethora of biological entities that can contribute to alleviate numerous human ailments. Algae are one such photosynthetic microorganism found in both marine as well as fresh water which are rich source of metabolites known for their nutrient content and health benefits. Various algal species like Haematococcus, Diatoms, Griffithsia, Chlorella, Spirulina, Ulva, etc. have been identified and isolated to produce biologically active and pharmaceutically important high value compounds like astaxanthin, fucoxanthin, sulphur polysaccharides mainly galactose, rhamnose, xylose, fucose etc., which show antimicrobial, antifungal, anti-cancer, and antiviral activities. However, the production of either of these bio compounds is favored under conditions of stress. This review gives detailed information on various nutraceutical metabolites extracted from algae. Additionally focus has been made on the role of these bio compounds extracted from algae especially sulphur polysaccharides to treat several diseases with prospective treatment for SARS-CoV-2. Lastly it covers the knowledge gaps and future perspectives in this area of research.

Perovskite-based solar cells fabricated from TiO2 nanoparticles hybridized with biomaterials from mollusc and diatoms.

Perovskite solar cells (PVSCs) convert solar energy into electrical energy. Current study employs fabrication of PVSCs using calcium titanate (CaTiO3) prepared by co-precipitation of TiO2 nanoparticle (NP) and CaCO3 NP with later synthesized from mollusc shell. Furthermore, frustules of diatom, Nitzschia palea were used to prepare silica doped CaTiO3 (Si-CaTiO3) nanocomposite. CaTiO3 NP and Si-CaTiO3 nanocomposites film were made on fluorine doped tin oxide (FTO) glass plate using spin coater separately for two different kinds of PVSCs tested at different intensities of light. The perovskite materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX) spectroscopy. Thickness of the film was measured by profilometer. The maximum power density (PDmax) of CaTiO3 made PVSCs was 0.235 mW/m2 under white LED light and 0.041 mW/m2 in broad spectrum light. Whereas, PDmax of PVSCs with Si-CaTiO3 was higher about 0.0083 mW/m2 in broad spectrum light and was 0.0039 mW/m2 in white LED light. This is due to the fact that CaTiO3 allowed blue and red light in broad spectrum to pass through it without being absorbed compared to white LED light which gets reflected. On the offset, in PVSC made of Si-CaTiO3 since diatoms frustules are made up of nanoporous architecture it increases the overall porosity of PVSC making them potentially more efficient in broad spectrum of light compared to white LED light.

Diatom microalgae as smart nanocontainers for biosensing wastewater pollutants: recent trends and innovations.

Microalgae have been recognized as one of the most efficient microorganisms to remediate industrial effluents. Among microalgae diatoms are silica shelled unicellular eukaryotes, found in all types of water bodies and flourish very well even in wastewater. They have their silica cell wall made up of nano arrayed pores arranged in a uniform fashion. Therefore, they act as smart nanocontainers to adsorb various trace metals, dyes, polymers, and drugs which are hazardous to human as well to aquatic life. The beautiful nanoarchitecture in diatoms allows them to easily bind to ligands of choice to form a nanocomposite structure with the pollutants which can be a chemical or biological component. Such naturally available diatom nanomaterials are economical and highly sensitive compared to manmade artificial silica nanomaterials to help in facile removal of the toxic pollutants from wastewater. This review is thus focused on employing diatoms to remediate various pollutants such as heavy metals, dyes, hydrocarbons detected in the wastewater. It also includes different microalgae as biosensors for determination of pollutants in effluents and the perspectives for nanotechnological applications in the field of remediating pollutants through microalgae. The review also discusses in length the hurdles and perspectives of employing microalgae in wastewater remediation.