•Bioremediation of five toxic heavy metals by microalgae were reviewed in-depth.•Feasibility and potential of value-added product accumulation were evaluated.•Discussion of advanced techniques and ...integration with other technologies.•Challenges and proposed strategies were summarized along with future prospects.
Five heavy metals namely, arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb) and mercury (Hg) are carcinogenic and show toxicity even at trace amounts, posing threats to environmental ecology and human health. There is an emerging trend of employing microalgae in phycoremediation of heavy metals, due to several benefits including abundant availability, inexpensive, excellent metal removal efficiency and eco-friendly nature. This review presents the recent advances and mechanisms involved in bioremediation and biosorption of these toxic heavy metals utilizing microalgae. Tolerance and response of different microalgae strains to heavy metals and their bioaccumulation capability with value-added by-products formation as well as utilization of non-living biomass as biosorbents are discussed. Furthermore, challenges and future prospects in bioremediation of heavy metals by microalgae are also explored. This review aims to provide useful insights to help future development of efficient and commercially viable technology for microalgae-based heavy metal bioremediation.
Heavy metal pollution is one of the most pervasive environmental problems globally. Novel finely tuned algae have been proposed as a means to improve the efficacy and selectivity of heavy metal ...biosorption. This article reviews current research on selective algal heavy metal adsorption and critically discusses the performance of novel biosorbents. We emphasize emerging state-of-the-art techniques that customize algae for enhanced performance and selectivity, particularly molecular and chemical extraction techniques as well as nanoparticle (NP) synthesis approaches. The mechanisms and processes for developing novel algal biosorbents are also presented. Finally, we discuss the applications, challenges, and future prospects for modified algae in heavy metal biosorption.
Novel finely tuned algae can improve the selectivity and performance of heavy metal adsorption.Molecular modification can be used to display metal-binding proteins at the cell surface via gene overexpression or by introducing exogenous DNA to generate transgenic algae.The performance of chemical modification has been highly variable, and more studies will be necessary to overcome its limitations.The extraction approach is promising because of the strong metal-binding properties of algae that have been attributed to alginate.Algae-based nanoparticles show better performance in heavy metal removal compared with raw algae.
The quest for a chemical surfactant substitute has been fuelled by increased environmental awareness. The benefits that biosurfactants present like biodegradability, and biocompatibility over their ...chemical and synthetic counterparts has contributed immensely to their popularity and use in various industries such as petrochemicals, mining, metallurgy, agrochemicals, fertilizers, beverages, cosmetics, etc. With the growing demand for biosurfactants, researchers are looking for low-cost waste materials to use them as substrates, which will lower the manufacturing costs while providing waste management services as an add-on benefit. The use of low-cost substrates will significantly reduce the cost of producing biosurfactants. This paper discusses the use of various feedstocks in the production of biosurfactants, which not only reduces the cost of waste treatment but also provides an opportunity to profit from the sale of the biosurfactant. Furthermore, it includes state-of-the-art information about employing municipal solid waste as a sustainable feedstock for biosurfactant production, which has not been simultaneously covered in many published literatures on biosurfactant production from different feedstocks. It also addresses the myriad of other issues associated with the processing of biosurfactants, as well as the methods used to address these issues and perspectives, which will move society towards cleaner production.
Offering a potential solution for global food security and mitigating environmental issues caused by the expansion of land-based food production, the carbon-hunger and nutrient-rich microalgae ...emerged as a sustainable food source for both humans and animals. Other than as an alternative source for protein, microalgae offer its most valuable nutrients, omega-3 and 6 long-chain polyunsaturated fatty acids where the content can compete with that of marine fish with lower chemicals contamination and higher purity. Furthermore, the colorful pigments of microalgae can act as antioxidants together with many other health-improving properties as well as a natural colorant. In addition, the supplementation of algae as animal feed provides plentiful benefits, such as improved growth and body weight, reduced feed intake, enhanced immune response and durability towards illness, antibacterial and antiviral action as well as enrichment of livestock products with bioactive compounds. The significant breakthrough in algal biotechnology has made algae a powerful “cell factory” for food production and lead to the rapid growth of the algal bioeconomy in the food and feed industry. The first overview of this review was to present the general of microalgae and its potential capability. Subsequently, the nutritional compositions of microalgae were discussed together with its applications in human foods and animal feeds, followed by the exploration of their economic feasibility and sustainability as well as market trends. Lastly, both challenges and future perspectives were also discussed.
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•Microalgae offer solutions for a sustainable food source.•Microalgae contain vast nutritional compounds for food and feed products.•Microalgal-based feed and food provide better growth and health benefits.•The market trend of algal-based products enables sustainable bioeconomy.•Biotechnology breakthrough made algae a powerful “cell factory” for food production.
Microalgae are being promoted as a superior alternative feedstock for sustainable biofuel production and recently they are also being increasingly recognized as phytoremediation agents in ...bioremediation. Other than these, microalgae have been utilized as a sustainable feed in aquaculture for many years. The success of microalgae as a feed is based on the nutritional quality of microalgae, which are rich in protein, carbohydrates, fats, vitamins, minerals, and other beneficial biologically active components such as carotenoids and polyunsaturated fatty acids. Standards for the evaluation of microalgae include the assessment of various qualities such as digestibility, bioavailability, and toxicity analysis. This review provides comprehensive information regarding the current status and desirable characteristics of microalgae as a feed ingredient. Feed quality assessments such as protein quality, toxicological and microbiological analysis for microalgae are discussed. The techno-functional components of microalgae are presented in the feed perspective. The utilization of microalgae in various animal husbandry sectors and aquaculture are summarized. The advantages – disadvantages of microalgae as a feed is also presented, along with future research prospects. In short, this review will provide an overall view of the nutritional quality of microalgae and its beneficial application as a sustainable feed ingredient.
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•Microalgal components in feed provide nutritional and functional value.•Techno-functional properties of microalgal biomolecules are reviewed.•Antioxidants and anti-inflammatory compounds improve stress tolerance in animals.•Immune modulators boost immune response and disease resistance in farm animals.•Prebiotic activity has the potential to reduce GHG emissions of the livestock industry.
•Different mushroom polysaccharides extraction methods are reviewed and compared•Different methods could affect MW distribution and monosaccharide composition•SWE achieves higher yield due to ...increasing acidic behavior and solubility of water•Study of microenvironment effect on polysaccharides bioactivity is very important
Mushroom-derived polysaccharides (especially β-glucans) are gaining much interest from researchers and industries recently due to their antioxidant, antitumor, immune-modulating activities, and other health benefits. Besides conventional extraction methods, a wide range of advanced extraction technologies is available nowadays for the recovery of these bioactive ingredients from mushrooms, such as ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), enzyme-assisted extraction (EAE), ultrasonic-microwave synergistic extraction (UMSE), subcritical water extraction (SWE), pulsed electric field-assisted extraction (PEFAE), aqueous two-phase extraction (ATPE), integrated extraction techniques, and other novel extraction technologies. This review describes the background of edible mushrooms, followed by the structural characteristics and biological activities of mushroom-derived polysaccharides. Then, the recent developments in the technologies used for the extraction of mushroom polysaccharides are discussed and summarized, together with their strengths and limitations as well as the underlying mechanisms. Finally, these advanced extraction techniques are compared and critically analyzed. Future outlook has also been proposed.
Microalgae serve as a promising source for the production of biofuels and bio‐based chemicals. They are superior to terrestrial plants as feedstock in many aspects and their biomass is naturally rich ...in lipids, carbohydrates, proteins, pigments, and other valuable compounds. Due to the relatively slow growth rate and high cultivation cost of microalgae, to screen efficient and robust microalgal strains as well as genetic modifications of the available strains for further improvement are of urgent demand in the development of microalgae‐based biorefinery. In genetic engineering of microalgae, transformation and selection methods are the key steps to accomplish the target gene modification. However, determination of the preferable type and dosage of antibiotics used for transformant selection is usually time‐consuming and microalgal‐strain‐dependent. Therefore, more powerful and efficient techniques should be developed to meet this need. In this review, the conventional and emerging genome‐editing tools (e.g., CRISPR‐Cas9, TALEN, and ZFN) used in editing the genomes of nuclear, mitochondria, and chloroplast of microalgae are thoroughly surveyed. Although all the techniques mentioned above demonstrate their abilities to perform gene editing and desired phenotype screening, there still need to overcome higher production cost and lower biomass productivity, to achieve efficient production of the desired products in microalgal biorefineries.
Microalgae serve as promising sources for the production of biofuels and bio‐based chemicals. Therefore, more powerful and efficient techniques should be developed to meet this need. This review provides latest information of development on genetic engineering of microalgae to achieve efficient production of the desired products in biorefinery.
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•SDBC showed excellent performance towards PDS activation for SMX removal.•Nitrogen doping and iron loading were key active sites on SDBC for PDS activation.•The SDBC/PDS system was a ...novel nonradical oxidation process predominated by 1O2.•SMX pathways by nonradical oxidation were firstly studied by DFT and experiment.•Energy cost analysis demonstrated the SDBC/PDS process was energy saving.
In this study, sludge-derived biochar (SDBC) was prepared and applied in peroxydisulfate (PDS) activation for sulfamethoxazole (SMX) degradation. Compared to the slight adsorption (16.5%) by SDBC alone and low direct oxidation (10.1%) by PDS alone, the SMX degradation rate was drastically increased to 94.6% in the combined SDBC/PDS system, suggesting that SDBC can successfully and efficiently activate PDS. The observed rate constant of the combined SDBC/PDS system was 48.3 times those of both PDS alone and SDBC alone processes. Material characterization and comparative experiments showed nitrogen doping and iron loading into the carbon layer might be the important active sites of the graphene-like SDBC material in PDS activation for SMX degradation. More importantly, singlet oxygen (1O2), instead of traditional sulfate radicals or hydroxyl radicals, was the predominant reactive species of the SDBC/PDS system, which involved a new nonradical oxidation method for PDS activation by SDBC. The SMX degradation pathways by the nonradical 1O2 oxidation were first studied by combining density functional theory (DFT) calculations with experimental results. Different from the well-known pathways of SMX through the cleavage of the sulfanilamide bond by the attack of radicals, the 1O2 was likely to attack the aniline ring of SMX to initiate and accelerate the decomposition process. Finally, the energy cost analysis of the SDBC/PDS system further demonstrated the possible and economic application of the SDBC/PDS technique for SMX degradation. Thus, this study proposed a novel and economic method for PDS activation through a new nonradical oxidation pathway predominated by 1O2, which also promoted the safe and efficient transformation of antibiotics or other contaminants by PDS activation processes.
•Potential of microalgae biorefinery for producing high value products is assessed.•Conventional processes of microalgae biorefinery are discussed.•Recent technologies on microalgae biorefinery are ...reviewed.•Techno-economic analysis and LCA assessment on microalgal biorefinery are addressed.•Advantages of microalgae biorefinery and derived high-value products are emphasized.
Microalgae have received much interest as a biofuel feedstock in response to the uprising energy crisis, climate change and depletion of natural sources. Development of microalgal biofuels from microalgae does not satisfy the economic feasibility of overwhelming capital investments and operations. Hence, high-value co-products have been produced through the extraction of a fraction of algae to improve the economics of a microalgae biorefinery. Examples of these high-value products are pigments, proteins, lipids, carbohydrates, vitamins and anti-oxidants, with applications in cosmetics, nutritional and pharmaceuticals industries. To promote the sustainability of this process, an innovative microalgae biorefinery structure is implemented through the production of multiple products in the form of high value products and biofuel. This review presents the current challenges in the extraction of high value products from microalgae and its integration in the biorefinery. The economic potential assessment of microalgae biorefinery was evaluated to highlight the feasibility of the process.
Pigments (mainly carotenoids) are important nutraceuticals known for their potent anti-oxidant activities and have been used extensively as high end health supplements. Microalgae are the most ...promising sources of natural carotenoids and are devoid of the toxic effects associated with synthetic derivatives. Compared to photoautotrophic cultivation, heterotrophic cultivation of microalgae in well-controlled bioreactors for pigments production has attracted much attention for commercial applications due to overcoming the difficulties associated with the supply of CO2 and light, as well as avoiding the contamination problems and land requirements in open autotrophic culture systems. In this review, the heterotrophic metabolic potential of microalgae and their uses in pigment production are comprehensively described. Strategies to enhance pigment production under heterotrophic conditions are critically discussed and the challenges faced in heterotrophic pigment production with possible alternative solutions are presented.
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