•Haematococcus pluvialis accumulates Bioastaxanthin under stress.•High Light intensity or red/blue light acts as stress inducers.•Transcriptomic study locates the upregulated genes for astaxanthin ...synthesis.•Enormous impact on Circular Bioeconomy if cost of harvest is decreased.
Haematococcus pluvialis is a green alga that can accumulate high astaxanthin content, a commercially demanding market keto food. Due to its high predicted market value of about 3.4 billion USD in 2027, it is essential to increase its production. Therefore, it is crucial to understand the genetic mechanism and gene expressions profile during astaxanthin synthesis. The effect of poly- and mono-chromatic light of different wavelengths and different intensities have shown to influence the gene expression towards astaxanthin production. This includes transcriptomic gene analysis in H. pluvialis underneath different levels of illumination stress. This review has placed the most recent data on the effects of light on bioastaxanthin production in the context of previous studies, which were more focused on the biochemical and physiological sides. Doing so, it contributes to delineate new ways along the biotechnological process with the aim to increase bioastaxanthin production while decreasing production costs.
Microbial electrochemical technologies (METs) are a group of innovative technologies that produce valuables like bioelectricity and biofuels with the simultaneous treatment of wastewater from ...microorganisms known as electroactive microorganisms. The electroactive microorganisms are capable of transferring electrons to the anode of a MET through various metabolic pathways such as direct (via cytochrome or pili) or indirect (through transporters) transfer. Though this technology is promising, the inferior yield of valuables and the high cost of reactor fabrication are presently impeding the large-scale application of this technology. Therefore, to overcome these major bottlenecks, a lot of research has been dedicated to the application of bacterial signalling, for instance, quorum sensing (QS) and quorum quenching (QQ) mechanisms in METs to improve its efficacy in order to achieve a higher power density and to make it more cost-effective. The QS circuit in bacteria produces auto-inducer signal molecules, which enhances the biofilm-forming ability and regulates the bacterial attachment on the electrode of METs. On the other hand, the QQ circuit can effectively function as an antifouling agent for the membranes used in METs and microbial membrane bioreactors, which is imperative for their stable long-term operation. This state-of-the-art review thus distinctly describes in detail the interaction between the QQ and QS systems in bacteria employed in METs to generate value-added by-products, antifouling strategies, and the recent applications of the signalling mechanisms in METs to improve their yield. Further, the article also throws some light on the recent advancements and the challenges faced while incorporating QS and QQ mechanisms in various types of METs. Thus, this review article will help budding researchers in upscaling METs with the integration of the QS signalling mechanism in METs.
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•Bacterial quorum sensing (QS) and quorum quenching (QQ) mechanisms are elucidated.•QS enhances the transmission of electrons required for bioelectricity production.•QQ mechanism has proven efficient in preventing membranes from biofouling.•QS and QQ ameliorate the performance of microbial electrochemical technologies.
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.
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•Textile wastewater are rich in dyes and need an economic action.•Microalgae are economic source of remediating industrial pollutants.•Biorefinery aspects of microalgae-based effluents remediation have been uncovered.•The diatom cell wall has high surface area and good adsorption rate.•Diatoms in microbial fuel cell generate bioelectricity and valuable components.
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.
The current study employs nanoengineering diatom and TiO
NPs to form diatom-Si-TiO
nanoengineered structures to fabricate a dye sensitized solar cell (DSSC) (
-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
-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 (PD
) of
-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
(astaxanthin) >
(anthocyanin) >
(anthocyanin) >
(anthocyanin) >
(betalains), respectively. Among all the natural dyes used, the PD
for the control ruthenium dye was 6.164 mW m
followed by the highest in astaxanthin natural dye from
(5.872 mW m
). Overall, the use of natural dye
-DSSC makes the fuel cell low cost and an alternative to conventional expensive, metal and synthetic dyes.
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•Hydrogen production from photosynthetic microalgae.•Biophotolysis and fermentation techniques narrated.•Genomic and metabolomic approach on hydrogen production discussed.•State of ...art techniques to enhance the hydrogen in microalgae capsuled.
Hydrogen (H2) is one of the renewable and sustainable energy since it reduces greenhouse gas emissions producing water in its purest form. However, the production of H2 from conventional thermochemical technologies needs a switchover to biological processes to avoid replenishment of nonrenewable energy reservoirs. This may include algae which switch over from oxygen to bioH2 production and simultaneously produce various renewable energy products like biomass, carbon storage products, biofuel, lipids and alcohol. On the offset, the selection of algae entrenched on its metabolic and genomic pathways to screen enzymes and genes enhancing the production of bioH2 inside algal cell is crucial. However, they can be an immense reservoir of bioH2 only if its pretreatment process is economized. The current review identifies the metabolic pathway, enzymes and genes involved for bioH2 production. The review also discusses the state of art techniques, advancements, challenges, and techno-economic aspects for sustainable bioH2 production.
Microalgae are considered as the major resource to produce biofuel. However, among many microalgae it is essential to screen those which are robust in their growth and accumulate abundant lipid in ...their cells leading to the formation of biofuel upon transesterification. Among the microalgal species, diatoms are one of the richest sources of crude oil that have been fossilized under the ocean beds for thousands of years. There are many limitations for entry of such biofuel in the commercial market in different sector of biofuel dependent industries. However, high yield and low cost of production are among the two important factors while screening any microalgae for biofuel production. Therefore, catalyst constitute important ingredients during transesterification process of biofuel formation. These catalysts are both homogenous and heterogenous and need to be screened about their cost and availability for manufacturing economical biofuel on large scale consumption for a way towards green vehicles which has zero carbon footprint and pollution.
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•Microalgal as green energy for biofuel with zero carbon footprint.•A conceptual review on algae bio-refinery from microalgae using different catalyst.•Economical biodegradable catalysts for efficient yield in biofuel narrated.•Combined effect catalysts in thermochemical techniques using microalgal biomass.
Natural astaxanthin has shown its potential value in food, pharmaceuticals and nutraceutical industries. It is found in yeasts, algae, salmons, shrimps etc. but its substantial amounts are ...biosynthesized in
Haematococcus pluvialis
. The
Haematococcus
cells can biosynthesize large amounts of astaxanthin under stress conditions during their red stage to enhance the astaxanthin accumulation and elevation of its productivity. The stress related conditions are best suited in wastewater and can be an economical way of cultivating microalgae for astaxanthin production compared to the artificial media simulated growth in indoor or outdoor photobioreactors. It is well known fact that industrial effluents are rich in various macro and micronutrients which promote algal growth but, in some condition, due to absence of some nutrients the microalgal cells of
Haematococcus
come in conditions of stress leading to high astaxanthin accumulation. The present review discusses microalgae responsible for producing astaxanthin under stress conditions and valorising the effluents from industrial wastewater. This is further associated with optimizing techniques for culturing microalgae with high biomass and its biocompounds. It also highlights the challenges and knowledge gaps in using wastewater as medium for large scale production of valuable biocompounds like astaxanthin, which paves way towards sustainable environment.
Graphical abstract
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.
•Textile dyes are hazardous pollutants bringing environmental stress and pollution.•Technological approaches to treat dyes have been narrated.•Application of algae in dead/live forms to treat dyes in a Microbial fuel cell have been discussed.•Algae acts as techno-economic resource for valorisation of industrial effluents.
Urbanization and industrialisation have led to an eruption of tannery industries in India and other countries at a rapid spur. These industries release lot of wastewaters during the cleaning and ...manufacture of leather hide. The wastewaters thus released directly into rivers and other waterbodies are abundantly rich in pollutants containing heavy metals due to chemicals and dyes used in tannery industries generated while cleaning these leather hides. The tannery wastewater (TWW) in such industries is mainly rich in chromium which enters our biological system directly or indirectly. This results in outbreak of various carcinogenic and genetic diseases not only in humans but also in animals and plants. Although there are many existing techniques to treat wastewater from the tannery industry, but biological methods using microalgae serves as most ecofriendly and environment friendly way. The phycoremediation occurs via adsorption, accumulation and consumption of various ions, metals, and chemical components present in TWW by microalgae. Further in this mitigating approach, microalgae simultaneously produce various value-added products. The present review addresses environmental sustainability and economy with respect to the electrochemical, nanotechnological and biotechnological aspect of using microalgae in the treatment of tannery waste effluents.
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