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•H. pluvialis is one of the abundant sources for production of natural astaxanthin.•Intensive discussion on the life cycle of H. pluvialis.•Advanced and conventional biorefinery ...techniques of astaxanthin are evaluated.•The future prospect and challenges were discussed in depth.
Haematococcus pluvialis is one of the most abundant sources of natural astaxanthin as compared to others microorganism. Therefore, it is important to understand the biorefinery of astaxanthin from H. pluvialis, starting from the cultivation stage to the downstream processing of astaxanthin. The present review begins with an introduction of cellular morphologies and life cycle of H. pluvialis from green vegetative motile stage to red non-motile haematocyst stage. Subsequently, the conventional biorefinery methods (e.g., mechanical disruption, solvent extraction, direct extraction using vegetable oils, and enhanced solvent extraction) and recent advanced biorefinery techniques (e.g., supercritical CO2 extraction, magnetic-assisted extraction, ionic liquids extraction, and supramolecular solvent extraction) were presented and evaluated. Moreover, future prospect and challenges were highlighted to provide a useful guide for future development of biorefinery of astaxanthin from H. pluvialis. The review aims to serve as a present knowledge for researchers dealing with the bioproduction of astaxanthin from H. pluvialis.
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•Persistent organic pollutants beget adverse effects on environment and ecosystem.•Conventional organic wastewater treatment is highly complex and expensive.•Microalgae-bacteria ...synergy shows several advantages to the economy and environment.•Microalgae-bacteria consortia is a latent wastewater treatment to remove POPs.•Mechanisms involved mainly via biosorption, bioaccumulation and biodegradation.
The litter of persistent organic pollutants (POPs) into the water streams and soil bodies via industrial effluents led to several adverse effects on the environment, health, and ecosystem. For the past decades, scientists have been paying efforts in the innovation and development of POPs removal from wastewater treatment. However, the conventional methods used for the removal of POPs from wastewater are costly and could lead to secondary pollution including soil and water bodies pollution. In recent, the utilization of green mechanisms such as biosorption, bioaccumulation and biodegradation has drawn attention and prelude the potential of green technology globally. Microalgae-bacteria consortia have emerged to be one of the latent wastewater treatment systems. The synergistic interactions between microalgae and bacteria could proficiently enhance the existing biological wastewater treatment system. This paper will critically review the comparison of conventional and recent advanced wastewater treatment systems and the mechanisms of the microalgae-bacteria symbiosis system.
In the context of climate change and the increase of the energy demand, there is a need for carbon sequestration methods and sustainable fuels. This can be done by cultivation of microalgae, an ...unicellular microscopic algae that converts carbon dioxide into high-value bioproducts and energy. Moreover, microalgae can be used to assess the health of ecosystems such as lakes. Here we review microalgae for biofuel, for wastewater treatment and as bioindicators. We discuss the impact of processes based on microalgae using life cycle assessment. We present co-cultivation of microalgae with other microbes, and we compare conventional processes with processes integrating auto-flocculation, in situ transesterification and excretion.
In the recent years, microalgae have captured researchers’ attention as the alternative feedstock for various bioenergy production such as biodiesel, biohydrogen, and bioethanol. Cultivating ...microalgae in wastewaters to simultaneously bioremediate the nutrient-rich wastewater and maintain a high biomass yield is a more economical and environmentally friendly approach. The incorporation of algal–bacterial interaction reveals the mutual relationship of microorganisms where algae are primary producers of organic compounds from CO
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, and heterotrophic bacteria are secondary consumers decomposing the organic compounds produced from algae. This review would provide an insight on the challenges and future development of algal–bacterial consortium and its contribution in promoting a sustainable route to greener industry. It is believed that microalgal-bacterial consortia will be implemented in the near-future for sub-sequential treatment of wastewater bioremediation, bioenergy production and CO
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fixation, promoting sustainability and making extraordinary advancement in life sciences sectors.
Heavy metal pollution remains a global environmental challenge that poses a significant threat to human life. Various methods have been explored to eliminate heavy metal pollutants from the ...environment. However, most methods are constrained by high expenses, processing duration, geological problems, and political issues. The immobilization of metals, phytoextraction, and biological methods have proven practical in treating metal contaminants from the soil. This review focuses on the general status of heavy metal contamination of soils, including the excessive heavy metal concentrations in crops. The assessment of the recent advanced technologies and future challenges were reviewed. Molecular and genetic mechanisms that allow microbes and plants to collect and tolerate heavy metals were elaborated. Tremendous efforts to remediate contaminated soils have generated several challenges, including the need for remediation methodologies, degrees of soil contamination, site conditions, widespread adoptions and various possibilities occurring at different stages of remediation are discussed in detail.
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•Impact of heavy metal toxicity towards the environment and human health.•Physical, chemical, and bioremediation approaches were used for contaminated soils.•Land filling, soil cleaning and solidification methods are well-established.•Treatability studies are crucial in the selection of soil sanitation techniques.•Future prospect and challenges of remediation would provide insights for readers.
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•An alternative and rapid approach for the recovery of astaxanthin from H. pluvialis.•Implementation of bubble-assisted technologies for the recovery of astaxanthin.•Optimization of ...various parameters for liquid biphasic flotation system.•Astaxanthin recovery of 78.38 ± 0.93 with extraction efficiency of 99.86 ± 0.05%
This work aimed to study the application of liquid biphasic flotation (LBF) for the efficient and rapid recovery of astaxanthin from H. pluvialis microalgae. The performance of LBF for the extraction of astaxanthin was studied comprehensively under different operating conditions, including types and concentrations of food-grade alcohol and salt, volume ratio, addition of neutral salt, flotation period, and mass of dried H. pluvialis biomass powder. The maximum recovery, extraction efficiency and partition coefficient of astaxanthin obtained from the optimum LBF system were 95.11 ± 1.35%, 99.84 ± 0.05% and 385.16 ± 3.87, respectively. A scaled-up LBF system was also performed, demonstrating the feasibility of extracting natural astaxanthin from microalgae at a larger scale. This exploration of LBF system opens a promising avenue to the extraction of astaxanthin at lower cost and shorter processing time.
Summary
Biofuel has emerged as an alternative source of energy to reduce the emissions of greenhouse gases in the atmosphere and combat global warming. Biofuels are classified into first, second, ...third and fourth generations. Each of the biofuel generations aims to meet the global energy demand while minimizing environmental impacts. Sustainability is defined as meeting the needs of the current generations without jeopardizing the needs of future generations. The aim of sustainability is to ensure continuous growth of the economy while protecting the environment and societal needs. Thus, this paper aims to evaluate the sustainability of these four generations of biofuels. The objectives are to compare the production of biofuel, the net greenhouse gases emissions, and energy efficiency. This study is important in providing information for the policymakers and researchers in the decision‐making for the future development of green energy. Each of the biofuel generations shows different benefits and drawbacks. From this study, we conclude that the first generation biofuel has the highest biofuel production and energy efficiency, but is less effective in meeting the goal of reducing the greenhouse gases emission. The third generation biofuel shows the lowest net greenhouse gases emissions, allowing the reduction of greenhouse gases in the atmosphere. However, the energy required for the processing of the third generation biofuel is higher and, this makes it less environmentally friendly as fossil fuels are used to generate electricity. The third and fourth generation feedstocks are the potential sustainable source for the future production of biofuel. However, more studies need to be done to find an alternative low cost for biofuel production while increasing energy efficiency.
• First generation biofuel has the highest biofuel yield and energy efficiency. However, the production of the biofuel opposed many sustainable development goals.
• Third and fourth generation biofuels show potential as a sustainable future green energy.
• Methods of lipid extraction of microalgae biofuel and environmental consequences of the fourth generation biofuel should be further explored.
The coexistence of algae and bacteria in nature dates back to the very early stages when life came into existence. The interaction between algae and bacteria plays an important role in the planet ...ecology, cycling nutrients, and feeding higher trophic levels, and have been evolving ever since. The emerging concept of algal-bacterial consortia is gaining attention, much towards environmental management and protection. Studies have shown that algal-bacterial synergy does not only promote carbon capture in wastewater bioremediation but also consequently produces biofuels from algal-bacterial biomass. This review has evaluated the optimistic prospects of algal-bacterial consortia in environmental remediation, biorefinery, carbon sequestration as well as its contribution to the production of high-value compounds. In addition, algal-bacterial consortia offer great potential in bloom control, dye removal, agricultural biofertilizers, and bioplastics production. This work also emphasizes the advancement of algal-bacterial biotechnology in environmental management through the incorporation of Industry Revolution 4.0 technologies. The challenges include its pathway to greener industry, competition with other food additive sources, societal acceptance, cost feasibility, environmental trade-off, safety and compatibility. Thus, there is a need for further in-depth research to ensure the environmental sustainability and feasibility of algal-bacterial consortia to meet numerous current and future needs of society in the long run.
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•Algal-bacterial consortia can tackle environmental issues.•Algae and bacteria are efficient in carbon capture and greenhouse gases mitigation.•Algal-bacterial technology fosters environmental sustainability in the green industry.•Industry 4.0 technologies can optimize performance and reduce ecological impacts.•In-depth research is vital to address the challenges of algal-bacterial biotechnology.
•Integration of ultrasound and liquid biphasic flotation for astaxanthin extraction.•Single-step cell disruptive extraction approach was carried out.•Optimization of various parameters for ...ultrasound-assisted liquid biphasic flotation.•Astaxanthin recovery of 83.73 ± 0.70% and partition coefficient of 157.83 ± 7.47.
The purpose of this investigation is to evaluate the implementation of ultrasound-assisted liquid biphasic flotation (LBF) system for the recovery of natural astaxanthin from Haematococcus pluvialis microalgae. Various operating conditions of ultrasound-assisted LBF systems such as the position of ultrasound horn, mode of ultrasonication (pulse and continuous), amplitude of ultrasonication, air flowrate, duration of air flotation, and mass of H. pluvialis microalgae were evaluated. The effect of ultrasonication on the cellular morphology of microalgae was also assessed using microscopic analysis. Under the optimized operating conditions of UALBF, the maximum recovery yield, extraction efficiency, and partition coefficient of astaxanthin were 95.08 ± 3.02%, 99.74 ± 0.05%, and 185.09 ± 4.78, respectively. In addition, the successful scale-up operation of ultrasound-assisted LBF system verified the practicability of this integrated approach for an effective extraction of natural astaxanthin.
In recent years, research studies on enzyme immobilized materials toward water pollution monitoring and remediation have increased considerably. This review focuses on the application of enzymes ...(e.g., laccase, acetylcholinesterase, tyrosinase, etc.,) immobilized nanomaterials in electrochemical sensing and biocatalytic degradation of some water pollutants. The need and advantages of nanomaterials as support for enzymes were deduced. Different methods developed for enzyme immobilization on nanomaterials were outlined. The sensing performances of enzyme immobilized nanomaterials modified electrodes toward organic pollutants including phenolic compounds, and pesticides were described. The biocatalytic properties of enzyme immobilized nanomaterials toward the degradation of organic pollutants including phenols, dyes, antibiotics, personal care products, and pesticides were discussed. Influencing methods like addition of synthetic mediators and light have also been pointed-out. The significance of nanomaterials in enzymatic sensing and catalytic degradation properties were highlighted. Current challenges and further research identified through this review have also been provided. The conclusions drawn from this literature review were presented.
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