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The rapid increase in fossil fuel depletion, environmental degradations, and industrialization have encouraged the need and production of sustainable fuel alternatives. This has led to the increase in interest in biofuels, especially third-generation biofuels produced from microalgae since they do not compete with food and land supplies. However, the global share for these biofuels has been inadequate recently, especially due to the ongoing global pandemic. Therefore, this paper offers a review of the state-of-the-art study of the production field of third-generation biofuel from microalgae. The current review aims to focus on the different aspects of algal biofuel production that requires further attention to produce it at a large scale. It was found that several strategies during the life cycle of algal biofuel production can significantly increase its quality and yield while reducing cost, energy, and other related attributes. This paper also focuses on the challenges for large-scale production of third-generation biofuels pre and post COVID-19 to better understand the barriers. The high cost of this fuel's production and sale tends to be the major reason behind the lack of large-scale production, hence, inadequacy to meet the global need. Third-generation biofuel has so much to offer including many integrated applications and advanced uses in the future fuel industry. Therefore, it is important to cope with the ongoing circumstances and emphasize the future of algal biofuel as a sustainable source. [ABSTRACT FROM AUTHOR]

The treatment of living organisms is a critical aspect of various environmental and industrial applications, ranging from wastewater treatment to aquaculture. In recent years, algal-based hollow fiber membrane bioreactors (AHFMBRs) have emerged as a promising technology for the sustainable and efficient treatment of living organisms. This review provides a comprehensive examination of AHFMBRs, exploring their integration with algae and hollow fiber membrane systems for diverse applications. It also examines the applications of AHFMBRs in various areas, such as nutrient removal, wastewater treatment, bioremediation, and removal of pharmaceuticals and personal care products. The paper discusses the advantages and challenges associated with AHFMBRs, highlights their performance assessment and optimization strategies, and investigates their environmental impacts and sustainability considerations. The study emphasizes the potential of AHFMBRs in achieving enhanced nutrient removal, bioremediation, and pharmaceutical removal while also addressing important considerations such as energy consumption, resource efficiency, and ecological implications. Additionally, it identifies key challenges and offers insights into future research directions. Through a systematic analysis of relevant studies, this review aims to contribute to the understanding and advancement of algal-based hollow fiber membrane bioreactors as a viable solution for the treatment of living organisms. [ABSTRACT FROM AUTHOR]

Algal biomass is a promising renewable feedstock for biofuel production that does not compete with food crops or require complex pretreatment like lignocellulosic biomass. This study examined biofuel production from two algae: Alkalinema pantanalense (cyanobacteria) and Chlorella vulgaris (green alga). Although there was no significant difference in their biomass, A. pantanalense showed a higher carbohydrate content (204.96 mg L−1) than C. vulgaris (156.07 mg L−1). To maximize reducing sugar release, three pretreatments were tested: thermotacidic, biological using the new fungal isolate Trichoderma longibrachiatum , and biological with nanoparticles. Biological pretreatment with Mg Zn ferrite nanoparticles (MZF-nps) at 60 mg L−1 concentration gave the best results, significantly enhancing cellulase, β-glucosidase and filter paper cellulase activities by 20.94 % (A. pantanalense) and 18.63 % (C. vulgaris). For biohydrogen production, the co-culture of Klebsiella pneumoniae and Enterobacter cloacae resulted in faster fermentation and improved hydrogen evolution compared to individual cultures. A. pantanalense and C. vulgaris yields were 35.1 mL g−1 and 26.6 mL g−1 dry weight, with maximal cumulative production of 2478 mL L−1 and 1845 mL L−1, respectively. Optimized Saccharomyces cerevisiae bioethanol fermentation conditions included 72 h incubation, 5 % inoculum, 30 °C, pH 5 under shaking condition, yielded 11.2 g L−1 (A. pantanalense) and 7.2 g L−1 (C. vulgaris). Furthermore, MZF-nps hydrolysate significantly increased bioethanol production, by 4.2-fold (A. pantanalense) to 32.45 g L−1 and 3.48-fold (C. vulgaris) to 28.6 g L−1, compared to thermoacidic pretreatment. In summary, biological pretreatment demonstrates the potential of algal biomass as a renewable feedstock for sustainable biofuel production. • Algal biomass is a promising renewable feedstock for biofuel production. • Biological pretreatment with nanoparticles increased fermentable sugars and biofuel yields. • Optimized fermentation conditions improved bioethanol yields from algal biomass. • MZF-NP increased bioethanol production up to 4.2-fold over thermoacidic pretreatment. • Co-culturing bacteria improved biohydrogen yield from algal biomass over individual strains. [ABSTRACT FROM AUTHOR]

The microalgae Chlorella vulgaris and Tetraselmis chuii offer several attractive attributes as aquaculture feed. Biomass production of C. vulgaris and T. chuii is relatively expensive because it requires high operation and substrate cost. Use of food industry waste is one of the promising solutions to reduce the substrate cost. In this research the impact of diverse concentration was filtered and centrifuged, food wastewater (FWW) was scrutinized as an alternative intermediate for microalgal bioremediation, lipid yield and cell growth. C. vulgaris had superior lipid accumulation and cell growth at 75% level and T. chuii had enhanced lipid accumulation and cell growth at 75% with the most explicit growth rate (0.27 d− 1) and maximum biomass formation rate (0.1–0.18 gL− 1 d− 1) and lipid content (33.80 ± 0.88% and 35.04 ± 2.05%) respectively. The microalgae cells not only improved with FWW feeding and the level of COD (80.97–66.17%), BOD (81.13–66.81%), TN (55.88–22.06%) and certain heavy metals like zinc (99.72–99.52%) manganese (72.09–65.17%) nickel (50.68–34.41%), NO3N (50.68–42.59%) ferric (57.14–65.71%) cadmium (83.51–86.64%) lead (48.83–97.21%) and arsenic (55.13–55.00%) were efficiently removed from FWW at different dilution concentrations. C18:0/C18:1 were the major fatty acids in lipids which show a vast potential of microalgae for biodiesel fabrication and instantaneous bioremediation procedure using FWW. [ABSTRACT FROM AUTHOR]

Bioethanol is attracting increasing attention as a sustainable alternative to fossil fuels. Depending on the feedstock, it is classified into four generations. First-generation bioethanol, sourced from food crops, has higher feedstock costs but lower processing costs; however, it may lead to food scarcity. Second-generation bioethanol uses low-cost lignocellulosic feedstocks and can be adopted widely. However, despite the technological development in second-generation bioethanol, cost of processing is still high, making second-generation bioethanol uncompetitive with gasoline. Third-generation bioethanol primarily relies on algae, while fourth-generation bioethanol uses genetically modified algae to enhance bioethanol yield. Current bioethanol production mainly comes from the first-generation route, while second-generation bioethanol is slowly taking off. Third- and fourth-generation bioethanol production is still in the lab and pilot stages. This review critically discusses and summarizes recent advancements in all four generations of bioethanol production. It highlights significant findings regarding different raw materials, processing methods, process parameters, and microorganisms involved. Further, the paper delves into the economic viability and current deployment status of various bioethanol production routes by summarizing the techno-economic analysis done and some of the commissioned plants, along with their technology readiness level. The current challenges associated with different routes are outlined while offering insights into future perspectives. [Display omitted] • Critical analysis of developments in bioethanol synthesis across diverse feedstocks. • Factors influencing different generations of bioethanol production are outlined. • Pretreatment methods aiding in enhanced bioethanol yield. • Explores economic viability and deployment status across all bioethanol generations. • Highlights challenges faced and pinpoint critical factors for process improvements. [ABSTRACT FROM AUTHOR]

Algae has a great CO2 biofixation potential that plays crucial role in regulating global carbon cycle and sustaining the ecology. Biosequestration of carbon is more efficient, sustainable, and has broader spectrum than its sequestration via various synthetic means. This study has analyzed the carbon sequestration potential of algae of Uchalli Wetland Complex (UWC) to mimic the natural microalgae function to realize the ecological significance of the complex being an important Ramsar site. The microalgal mats/colonies were sampled from three lakes, i.e., Khabeki, Uchalli, and Jahlar lakes, for consecutive eight months with an interval of 30 days to determine the carbon sequestration potential of the UWC. Maximum percentages of carbon (25.33–31.55%), hydrogen (3.86–4.68%), and nitrogen (2.9–3.45%) in the microalgal mats of Jahlar Lake, whereas highest sulfur content (5.9–7.42%) was observed in microalgal colonies of Khabeki Lake. Growth kinetics depicts maximum biomass productivity (4.5 × 106 avg.) in September while maximum CO2 sequestration (75.7 g−2 month−1) is detected in algal mats of Uchalli Lake. This study explored an undiscovered carbon sequestering potential of about 108.6 g−2 month−1 of algae of UWC that is certainly assistive in combating the climate change. Pearson's correlation generated significant relationships among different studied parameters at 0.01 and 0.05 levels. Statistical analysis by ANOVA with respect to lakes showed significant values (p = 0.000–0.003) of pH, salinity, carbon, nitrogen, hydrogen, sulfur, CO2 fixed, C/N, and C/H. [ABSTRACT FROM AUTHOR]

Featured Application: Anaerobic co-digestion of waste biomass in a two-stage anaerobic process was successful, and sequential production of biohydrogen and biomethane was realized, minimizing waste disposal and realising additional energy output for possible replacement of fossil fuels in a green way. Green and sustainable economies have recently become a key issue in long-term growth and well-being. Co-digestion of various waste materials in an eco-friendly way through biogas production has become the preferred method for their utilization and valorization. The possibility of hydrogen and methane yield maximization depends on the most suitable alkali reagent for pretreatment of waste lignocellulosic material, which was revealed in batch tests to determine the hydrogen production potential. The mixture for digestion consisted of pretreated wheat straw mixed with waste algal biomass in a ratio of 80:20 (w/w). The maximum hydrogen yield was achieved after applying sodium hydroxide thermoalkaline pretreatment, with a two-fold higher yield than the untreated control. Hydrogen production was stable and methane was not present in the resultant gas. The influence of the hydraulic retention time (HRT) on the maintenance of cascade installation was studied. The maximum daily concentration of hydrogen was achieved at an HRT of 2 days—42.5% H2—and the maximum concentration of methane was 56.1% at an HRT of 6 days. Accumulation of volatile fatty acids was registered in the first step and their depletion was noted in the second one. The obtained values of the cellulose content demonstrated that it was utilized by up to 2.75% in the methanogenic bioreactor at the end of the process. Metagenomics analyses revealed the bacteria Thermocaproicibacter melissae (44.9%) and Clostridium cellulosi (41.9%) participated in the consortium, accomplishing substrate hydrolysis and acidogenesis in the first stage. Less in abundance were Thermoanaerobacterium butyriciformans, Calorimonas adulescens, Pseudomonas aeruginosa and Anaerocolumna chitinilytica. Methanogenesis was performed by an archaeon closely related to Bathyarchaeota (99.5%) and Methanobacterium formicicum. The most abundant bacterial strains in the methanogenic fermenter were Abyssalbus ytuae (30%), Proteiniphilum acetatigenes (26%) and Ruficoccus amylovorans (13%). [ABSTRACT FROM AUTHOR]

Wastewater treatment and simultaneous production of value-added products with microalgae represent a sustainable alternative. Industrial wastewater, characterized by high C/N molar ratios, can naturally improve the carbohydrate content in microalgae without the need for any external source of carbon while degrading the organic matter, macro-nutrients, and micro-nutrients. This study aimed to understand the treatment, reuse, and valorization mechanisms of real cooling tower wastewater (CWW) from a cement-processing industry mixed with domestic wastewater (DW) to produce microalgal biomass with potential for synthesis of biofuels or other value-added products. For this purpose, three photobioreactors with different hydraulic retention times (HRT) were inoculated simultaneously using the CWW-DW mixture. Macro- and micro-nutrient consumption and accumulation, organic matter removal, algae growth, and carbohydrate content were monitored for 55 days. High COD (> 80%) and macronutrient removals (> 80% of N and P) were achieved in all the photoreactors, with heavy metals below the limits established by local standards. The best results showed maximum algal growth of 1.02 g SSV L−1 and 54% carbohydrate accumulation with a C/N ratio of 31.24 mol mol−1. Additionally, the harvested biomass presented a high Ca and Si content, ranging from 11 to 26% and 2 to 4%, respectively. Remarkably, big flocs were produced during microalgae growth, which enhanced natural settling for easy biomass harvesting. Overall, this process represents a sustainable alternative for CWW treatment and valorization, as well as a green tool for generating carbohydrate-rich biomass with the potential to produce biofuels and fertilizers. [ABSTRACT FROM AUTHOR]

Benthic algae and autotrophic seston are important bases of stream food webs, and several different environmental factors may influence their biomass. We explored how benthic algae and autotrophic seston biomass (using chlorophyll-a as a proxy for algal biomass) were associated with stream temperature, channel width, canopy cover, stream cardinal orientation, benthic macroinvertebrate functional feeding group abundance, salmonid biomass, and water velocity in 16 small, fish-bearing streams in the temperate rainforest of the Olympic Peninsula in Washington State, USA, in the summer of 2020. We performed a mixed-effects regression analysis of extracted chlorophyll-a (chl-a) and then used model averaging to determine significant (α = 0.05) algal–environmental associations for benthic algae and autotrophic seston separately. We found that benthic algae chl-a concentration increased significantly with stream temperature (p = 0.0085) and decreased significantly with water velocity (p = 0.0053). For autotrophic seston, we found that chl-a concentration increased significantly with benthic macroinvertebrate predator abundance (p = 0.0007) and stream temperature (p = 0.0160). This study underscores the need to consider a broad range of environmental variables when making research and management decisions concerning stream ecology. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris is of great importance in numerous exploratory or industrial applications (e.g., medicals, food, and feed additives). Rapid quantification of algal biomass is crucial in photobioreactors for the optimization of nutrient management and the estimation of production. The main goal of this study is to provide a simple, rapid, and not-resource-intensive estimation method for determining the algal density of C. vulgaris according to the measured parameters using UV–Vis spectrophotometry. Comparative assessment measurements were conducted with seven different methods (e.g., filtration, evaporation, chlorophyll a extraction, and detection of optical density and fluorescence) to determine algal biomass. By analyzing the entire spectra of diluted algae samples, optimal wavelengths were determined through a stepwise series of linear regression analyses by a novel correlation scanning method, facilitating accurate parameter estimation. Nonlinear formulas for spectrometry-based estimation processes were derived for each parameter. As a result, a general formula for biomass concentration estimation was developed, with recommendations for suitable measuring devices based on algae concentration levels. New values for magnesium content and the average single-cell weight of C. vulgaris were established, in addition to the development of a rapid, semiautomated cell counting method, improving efficiency and accuracy in algae quantification for cultivation and biotechnology applications. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) are commonly used chemicals in various industries and are conventionally produced by the reaction of polyols and diisocyanates. However, synthetic petroleum-based polymers are non-biodegradable and resulting in issues like waste disposal, risks to aquatic and terrestrial ecosystems. In this study, a novel microalgal protein-based ultraviolet (UV) curing polyurethane acrylate (PUA) was prepared with hexanediol diacrylate (20% HDDA) precursor, amino acid oligomers, and photoinitiator (Irgacure 184). Experimental conditions for the synthesis of precursors were studied and their chemical structures were confirmed by FT-IR, 1HNMR, 13CNMR, and differential scanning calorimetry (DSC). The absorption peak at 1695 cm−1 confirmed the formation of a urethane bond. For instance, the obtained polyurethane acrylate coating (PUA) possessed a glass transition temperature (Tg) of 122 ℃, tensile strength, modulus of 19.1 MPa, 465 MPa, and lower elongation break (6%). While using reactive diluents, the coating compositions showed significant enhancement of mechanical, physical, and chemical resistance properties. In general, this work offered a simple bio-scheme of reactions to prepare a sustainable microalgal-based PU coating that could be applied in the coating industry with improved properties. [ABSTRACT FROM AUTHOR]

Fertilisers and pesticides are increasingly used in agriculture to improve productivity and protect crops from fungi and insects. However, these farm inputs may lead to adverse effects on aquatic biodiversity through eutrophication and pesticide toxicity. This study aimed to establish the effects of nutrient-only, pesticide-only, combined nutrients and pesticides, and control on the abundance of Daphnia magna, and algal biomass. In each of the treatments, different concentrations of nutrients and pesticides residues were added separately or in combination. Responses were measured every 24 h, and the experiments ended after 168 h of exposure. The experiment was set in four concentration treatments comprising high, moderately high, moderately low, and low concentrations. Data analysis was done using Multiple Analysis of Variance (MANOVA) and ANOVA to determine the effect of time, concentrations and the interaction of time and concentrations for each of the treatments on D. magna abundance, and algal biomass. Higher concentrations of pesticide additives were associated with lower abundance of D. magna, and higher algal biomass over the exposure periods. There was a significant reduction in the abundance of D. magna in the combined treatment indicating the toxic effect of pesticide addition. Determination of effect concentrations based on combined nutrients-pesticides experiments becomes important in setting water quality standards, and monitoring the quality status, to avoid underestimating the ecological implications of combined contamination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Renewable biofuel production by algal biomass has been discussed in this review. • Two major thermochemical process like pyrolysis and hydrothermal liquefaction are described. • Different pyrolysis and HDL methods in fuel production has been explained. • Temperature, heating rate of the process and product yield have been focused. • Challenges and future benefits of the fuel production using algal biomass is detailed. Renewable and sustainable biofuel production from algal biomass has been explored vigorously due to the owing potential of overcoming the limitations of first and second-generation biofuel feedstocks. Thermochemical conversion technologies are considered promising routes for bioenergy production from algal biomass and have been extensively investigated over the last few years. This paper aims to review the various pyrolysis (slow, fast, and microwave -assisted) processes and hydrothermal liquefaction (HTL) techniques. The fast pyrolysis is involving a higher heating rate and shorter residence time compared to slow pyrolysis. Microwave-assisted pyrolysis (MAP) is considered a highly efficient process due to uniform heating. Due to a high moisture feedstock, the HTL process is considered the most energy-efficient processing option for algal biomass. In all these processes, the process temperature is considered the most critical parameter affecting product yield. This paper provides a detailed analysis and discussion on the effect of temperature and heating rates on the product (biochar, bio-oil, and syngas) yields for various microalgal species. The process details, different approaches, and process conditions investigated, challenges and recent advancements achieved in both technologies have been discussed in detail that provides useful insights to design a sustainable process and understand the process feasibility. [ABSTRACT FROM AUTHOR]

Eutrophication is one of the major emerging challenges in aquatic environment. Industrial facilities, including food, textile, leather, and paper, generate a significant amount of wastewater during their manufacturing process. Discharge of nutrient-rich industrial effluent into aquatic systems causes eutrophication, eventually disturbs the aquatic system. On the other hand, algae provide a sustainable approach to treat wastewater, while the resultant biomass may be used to produce biofuel and other valuable products such as biofertilizers. This review aims to provide new insight into the application of algal bloom biomass for biogas and biofertilizer production. The literature review suggests that algae can treat all types of wastewater (high strength, low strength, and industrial). However, algal growth and remediation potential mainly depend on growth media composition and operation conditions such as light intensity, wavelength, light/dark cycle, temperature, pH, and mixing. Further, the open pond raceways are cost-effective compared to closed photobioreactors, thus commercially applied for biomass generation. Additionally, converting wastewater-grown algal biomass into methane-rich biogas through anaerobic digestion seems appealing. Environmental factors such as substrate, inoculum-to-substrate ratio, pH, temperature, organic loading rate, hydraulic retention time, and carbon/nitrogen ratio significantly impact the anaerobic digestion process and biogas production. Overall, further pilot-scale studies are required to warrant the real-world applicability of the closed-loop phycoremediation coupled biofuel production technology. • Nutrient-rich wastewater is a major cause of eutrophication in water bodies. • Algal biomass harvested from wastewater is a good substrate for biogas production. • Environmental factors affect the anaerobic digestion process. • Limited pilot-scale studies on phycoremediation coupled biogas production. • Algal blooms could be a valuable source for bioenergy production. [ABSTRACT FROM AUTHOR]

The rising living standards of humans have a high demand for natural resources. Algal biomass has emerged as a substitute for conventional resources obtained from animals and plants. Compositionally, algae constitute extractable carbohydrates, proteins, lipids, and other valuable bioactive compounds (BACs) in abundance. BACs profusely derived from algal biomass include long-chain polysaccharides, fatty acids such as mono- and polyunsaturated fatty acids (MUFA and PUFA), phenols, and proteins. The coupling of wastewater with algae for resource recovery for the BACs extraction can serve as a source of plenteous biochemicals with high industrial values like pigments, polysaccharides, lipids, antioxidants, and growth-promoting compounds. Extracted algal BACs can incorporate in the manufacturing of numerous cosmetic products, pharmaceuticals, and nutraceuticals. The productivity and quality of algal produce are still low relative to their demand. Genetic engineering has emerged as a proven approach to enhance the quality and quantity of algal produces and provide a better avenue for biofuel and value-added chemicals productions. Currently, genetic engineering has grabbed significant attention from researchers, and continuous efforts are encouraged to improve industrially viable algal species that can satisfy future demand. This article focuses on the wide range of BACs derived from algae and wastewater for resource recovery, genetic engineering in algae for BACs, influencing processing parameters for genetic engineered algae, concerns associated with genetic engineered algae, and future perspective. [ABSTRACT FROM AUTHOR]

The treatment of living organisms is a critical aspect of various environmental and industrial applications, ranging from wastewater treatment to aquaculture. In recent years, algal-based hollow fiber membrane bioreactors (AHFMBRs) have emerged as a promising technology for the sustainable and efficient treatment of living organisms. This review provides a comprehensive examination of AHFMBRs, exploring their integration with algae and hollow fiber membrane systems for diverse applications. It also examines the applications of AHFMBRs in various areas, such as nutrient removal, wastewater treatment, bioremediation, and removal of pharmaceuticals and personal care products. The paper discusses the advantages and challenges associated with AHFMBRs, highlights their performance assessment and optimization strategies, and investigates their environmental impacts and sustainability considerations. The study emphasizes the potential of AHFMBRs in achieving enhanced nutrient removal, bioremediation, and pharmaceutical removal while also addressing important considerations such as energy consumption, resource efficiency, and ecological implications. Additionally, it identifies key challenges and offers insights into future research directions. Through a systematic analysis of relevant studies, this review aims to contribute to the understanding and advancement of algal-based hollow fiber membrane bioreactors as a viable solution for the treatment of living organisms.

Heavy metals, dyes and pharmaceutical pollutants in water environment are considered as serious threat to the human and animal health globally. Rapid development of industrialization and agricultural activities are the major source for eliminating the toxic pollutants into the aquatic environment. Several conventional treatment methods have been suggested for the removal of emerging contaminants from wastewater. Algal biosorption, among other strategies and techniques, is demonstrating to be a limited technical remedy that is more focused and inherently more efficient and helps remove dangerous contaminants from water sources. The different environmental effects of harmful contaminants, including heavy metals, dyes, and pharmaceutical chemicals, as well as their sources, were briefly compiled in the current review. This paper provides a comprehensive definition of the future possibilities in heavy compound decomposition by using algal technology, from aggregation to numerous biosorption procedures. Functionalized materials produced from algal sources were clearly proposed. This review further highlights the limiting factors of algal biosorption to eliminate the hazardous material. Finally, this study showed how the existence of algae indicates a potential, effective, affordable, and sustainable sorbent biomaterial for minimizing environmental pollution. [Display omitted] • Algal biosorption is the economically viable and low-energy technological solution. • Biosorption mechanisms of algal biomass towards hazardous pollutants are discussed. • Functionalized materials derived from algal technology are reviewed. • Limiting factors and reactors involved in algal biosorption were elucidated. • Prospects and recommendations for future works were summarized. [ABSTRACT FROM AUTHOR]

The accumulation of CO2 in the atmosphere carries with it severe consequences, and cities are responsible for 70% of CO2 emissions. With this initiative, we address how innovative green architecture can contribute to removing CO2 from the urban area by implementing elements that incorporate microalgae cultivation into architecture. The presented project incorporates two photobioreactor installations filled with water, where microalgae circulate through methacrylate tubes. Used as two architectural elements: a façade that can fix 720 kg of CO2 per year from the atmosphere and produce 400 kg of biomass that can be used as fertilizer in irrigation water; and three artificial trees that can fix 50 kg of CO2 and produce 28 kg of biomass. To test its efficiency, a Life Cycle Inventory was conducted and compared to the amount of CO2 fixed during its lifetime. It was concluded that the system would need 11.11 years to fix the CO2 produced and would have a negative CO2 impact of 27 tons of CO2 during the useful life of its materials. This project is a starting point towards developing a disruptive and experimental alternative with great potential, being the first in Spain and one of the first in the world. [ABSTRACT FROM AUTHOR]

Algal biomass is a prospective feedstock for the eco-sustainable production of many different products with added value, such as meals, feeds, and fuels. The remaining biomass from the algae can be used as raw material and can be transformed into useful secondary products after the important macromolecules have been removed. By optimizing algal biomass hydrolysate utilizing microbial fermentation, several studies demonstrated the generation of bioenergy (bioalcohol, biogas, and biohydrogen) and biochemicals (organic acids and biopolymers). Since the harvest and maintenance of sustainable algal cultivation incur considerable energy and economical prowess, developing products from algae remains a challenge to be countered in commercial applications. This is a typical bottleneck issue when processing algae for fuels or chemicals at the pilot scale. Implementation of integrated algae biorefinery methods can substantially reduce the cost of production and energy consumption. An algae-based green economy can be financially more viable and utilizable, especially for countries with weaker economies. This review's goal is to examine the implementation of integrated biorefineries for the recovery of bioproducts generated from algae and potential applications. In this context, the life cycle analysis and business elements of a unified algal biorefinery are also addressed. [ABSTRACT FROM AUTHOR]

The food industry is a high consumer of polymer packing materials, sealing materials, and engineering components used in production equipment. Biobased polymer composites used in the food industry are obtained by incorporating different biogenic materials into the structure of a base polymer matrix. Renewable resources such as microalgae, bacteria, and plants may be used as biogenic materials for this purpose. Photoautotrophic microalgae are valuable microorganisms that are able to harvest sunlight energy and capture CO2 into biomass. They are characterized by their metabolic adaptability to environmental conditions, higher photosynthetic efficiency than terrestrial plants, and natural macromolecules and pigments. The flexibility of microalgae to grow in either low-nutrient or nutrient-rich environments (including wastewater) has led to the attention for their use in various biotechnological applications. Carbohydrates, proteins, and lipids are the main three classes of macromolecular compounds contained in microalgal biomass. The content in each of these components depends on their growth conditions. In general, proteins represent 40–70% of microalgae dry biomass, followed by carbohydrates (10–30%) and lipids (5–20%). A distinctive feature of microalgae cells is the presence of light-harvesting compounds such as photosynthetic pigments carotenoids, chlorophylls, and phycobilins, which are also receiving growing interest for applications in various industrial fields. The study comparatively reports on polymer composites obtained with biomass made of two species of green microalgae: Chlorella vulgaris and filamentous, gram-negative cyanobacterium Arthrospira. Experiments were conducted to reach an incorporation ratio of the biogenic material into the matrix in the 5–30% range, and the resulting materials were characterized by their mechanical and physicochemical properties. [ABSTRACT FROM AUTHOR]

Microalgae are very important organisms as primary producers and have a wide range of applications in areas such as aquaculture, pharmaceuticals, medicine, biofuels, and others. In this study, the effect of temperature and salinity on growth, biomass, proximate composition, and lipid production of Chaetoceros calcitrans (Paulsen) and Thalassiosira weissflogii (Grunow) were investigated. The best growth rate (SGR) and highest biomass production were observed at 30°C and 30 ppt for C. calcitrans and at 30°C and 25 ppt for T. weissflogii. At these optimum temperature and salinity combinations, the maximum cell density was accomplished by day 12 for C. calcitrans (6.74 × 106 cells ml-1) and by day 10 for T. weissflogii (3.45 × 106 cells ml-1). The proximate composition during this period was 38.25 ± 0.99% protein, 16.96 ± 0.90% lipid, and 9.39 ± 0.59% carbohydrate in C. calcitrans, compared to 13.49 ± 0.28% protein, 10.43% ± 0.25% lipid and 16.49 ± 0.47% carbohydrate in T. weissflogii. Furthermore, over 35% of lipids in C. calcitrans were palmitic acid (C16), while in T. weissflogii, over 24% of lipids were myristic acid (C14). Although C. calcitrans exhibited higher lipid content than T. weissflogii, both species displayed higher levels of saturated (SFA) and monounsaturated (MUFAs) fatty acids and low levels of polyunsaturated fatty acids (PUFAs). The findings illustrated that under their optimum temperature and salinity combinations, both species might produce significant sources of lipids, which can be utilised in various activities such as aquaculture, pharmaceuticals, medicine, biofuels and others. [ABSTRACT FROM AUTHOR]

Short-term N-NH4+ and N-NO3− removal by Ulva pseudorotundata under different initial nutrient concentrations and biomass stocking densities were investigated, monitoring in parallel photosynthetic parameters obtained by Pulse-Amplitude-Modulation (PAM) fluorometry of chlorophyll-a and evaluating biomass characteristics (CHN, proteins, carbohydrates). The results showed that U. pseudorotundata cultivated under solar radiation in a land-based outdoor pilot scale system was efficient in removing N-NH4+ and N-NO3− even in concentrations as high as 500 µmol L–1 ensuring complete water remediation in a period of 24 h and in all experimental conditions tested, however differences were observed depending on the stocking density and type of N-source. Treatments with N-NH4+ showed faster N removal than those with N-NO3−, whilst treatments with N-NO3− required more photosynthetic energy. Part of the ammonium removed in the respective treatments may have been volatilized as a combined effect of the pH increase related to photosynthesis and aeration in the tanks. The results presented here establish the fundamental parameters for the use of U. pseudorotundata as a biofiltering organism for effluents with high concentrations of N-NH4+ and N-NO3−. [ABSTRACT FROM AUTHOR]

Microorganism‐assisted biohydrogen (BioH2) is an encouraging replacement of fossil‐based fuels as feasible preference for various chemical and mechanical processes. BioH2 is capable to reduce greenhouse gas emissions and solve environmental issues, therefore, numerous studies addressed optimization of operation design, microbial actions, certain addition of chemicals or nanoparticles, pretreatment of algal biomass, diminishing sensibility of enzymes towards O2, integration with different processes for biorefinery approach, reducing costs, bioelectrochemical cell membranes, and others. The present review focuses on model organisms employed for the microorganism‐assisted biohydrogen production. Metabolic pathways such as biophotolysis, photofermentation, and dark fermentation were discussed for providing deep insight of microorganism‐aided biohydrogen production. [ABSTRACT FROM AUTHOR]

Unsaturated vegetable oils with conjugated carbon–carbon double bonds, such as tung oil, can undergo free-radical polymerization, originating alternatives to petroleum-based materials. The introduction of fillers to vegetable oil-based polymer matrices results in composites with improved mechanical properties. In this work, thermosets were synthesized by the free-radical polymerization of a mixture of tung oil, divinylbenzene, and n-butyl methacrylate, and reinforced with bio-based fillers, namely Miscanthus, Pinus taeda (also known as southern pine), and algae (Microspora and Oedogonium) biomass. The effect of filler particle size on the composites' properties was evaluated. Additionally, to develop a better interaction between the hydrophobic resin and the hydrophilic reinforcements, and improve the mechanical properties of the composites prepared, itaconic anhydride, a bio-based molecule derived from itaconic acid, was added to the resin. Thermogravimetric analysis (TGA) showed that the presence of itaconic anhydride improved the overall thermal stability of the composites. The storage modulus of the composites at room temperature, assessed by dynamic mechanical analysis (DMA), was increased by approximately 32% and 68%, for Miscanthus and southern pine composites, respectively, when itaconic acid was added to the resin. It was also observed that the glass transition temperatures were not significantly affected by the presence of itaconic acid. Scanning electron microscope (SEM) images indicated better matrix-reinforcement adhesion in the presence of itaconic anhydride. [ABSTRACT FROM AUTHOR]

The use of liquid waste as a feedstock for cultivation of microalgae can reduce water and nutrient costs and can also be used to treat wastewater with simultaneous production of biomass and valuable products. This study applied strategies to treat diluted anaerobic digester effluent (ADE) as a residue of biogas reactors with moderate (87 ± 0.6 mg L−1; 10% ADE) and elevated NH4+-N levels (175 ± 1.1 mg L−1; 20% ADE). The effect of ADE dilution on the acclimatization of various microalgae was studied based on the analysis of the growth and productivity of the tested green algae. Two species of the genus Chlorella showed robust growth in the 10–20% ADE (with a maximum total weight of 3.26 ± 0.18 g L−1 for C. vulgaris and 2.81 ± 0.10 g L−1 for C. sorokiniana). The use of 10% ADE made it possible to cultivate the strains of the family Scenedesmaceae more effectively than the use of 20% ADE. The growth of Neochloris sp. in ADE was the lowest compared to other microalgal strains. The results of this study demonstrated the feasibility of introducing individual green microalgae into the processes of nutrient recovery from ADE to obtain biomass with a high protein content. [ABSTRACT FROM AUTHOR]

The present study investigates the sorption of four commercial dyes, namely Methylene Blue (MB), Malachite Green (MG), Indigo Carmine (IC), and Rhodamine B (RB) by dead biomass of Cladophora sp. The test alga exhibited the maximum sorption capacity (qmax) for MG (250.53 mg g−1) followed in decreasing order by MB (94.76), IC (63.20), and RB (16.50). The sorption of MB and MG was influenced by the initial pH of the solution. It increased consistently as pH increased from 2 to 8. Whereas sorption of the other two dyes, RB and IC, is almost pH-independent and decreased slightly as pH increased from 2 to 4. The sorption of all the test dyes by Cladophora biomass was rapid and the process attained equilibrium within 4–8 h. The general-order rate law appropriately fitted to the time course sorption data of all the test dyes (adj R2 > 0.989). The kinetic order of the sorption reaction varied from 1.62 to 3.77 for different dyes. Freundlich, Langmuir, Redlich-Peterson and Sips models suitably described the equilibrium sorption data of the test dyes. However, the last three models showed a marginal superiority over the Freundlich model by revealing a slightly higher adj R2 value for each studied dye. Nonetheless, the test biomass could be a suitable biosorbent as it rapidly sorbed the substantial amounts of both cationic and anionic dyes from the aqueous solutions and is also easily and widely available as a low-cost algal material. [ABSTRACT FROM AUTHOR]

Eutrophication and algal blooms have sparked worldwide concern because of their widespread effects on water-dependent species. Harmful algal blooms can cause fatal effects to lesser flamingos (Phoeniconaias minor), obligatory filter feeders and vital bio-indicators in soda lakes. Thus, early detection of algal blooms and potential indicators in water quality is critical, but general tools are lacking in eastern African soda lakes. We monitored algal biomass changes and related water physico–chemical variables for 12 consecutive months in the lakes Big Momella and Rishateni in northern Tanzania. We used chlorophyll-a to measure algal biomass and quantified water physico–chemical variables that might influence algae growth. We also monitored lesser flamingo numbers to understand trends across the year and according to algal bloom occurrence. Algal biomass was strongly related to water nitrogen (r = 0.867; p < 0.001) and phosphorus (r = 0.832; p < 0.001). Monthly patterns showed significant differences in water quality and algal biomass (F = 277, p < 0.001) but not across sampling sites (F = 0.029, p = 0.971). Lesser flamingo numbers seemed to be related to algal biomass at Lake Big Momella (r = 0.828; p < 0.001) and shortly after algal biomass peaked high (i.e., March and April 2021), flamingo numbers declined. Lake Rishateni showed similar patterns. Our findings can provide a basis towards understanding the factors contributing to temporal changes in lesser flamingo abundance due to spatio–temporal water quality variations, which is important for optimising conservation efforts for the species in these unique Momella lakes. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of microalgae and cyanobacteria was first proposed as a destination for algal biomass accumulated on stabilization ponds since it could not be disposed of directly in the environment. Now, the versatility of algal biomass makes them a suitable candidate to produce biofuels and other biomolecules in biorefineries. Anaerobic digestion of biomass is advantageous because it does not require the extraction of specific cellular constituents or drying of the biomass. Nevertheless, challenges remain regarding biomass concentration and their resistant cell walls, which are factors that could hamper methane yield. Many pretreatment methods, including chemical and thermochemical, have been proposed to break down the complex polymers present on the cell wall into smaller molecules. Unfortunately, the relationship between biomass solubilization and methane yield is not well defined. This article intends to review the anaerobic digestion of algal biomass and the role of chemical and thermochemical pretreatments in enhancing methane production. Several pretreatment conditions selected from the scientific literature were compared to verify which conditions actually improve methane yield. The severity of the selected pretreatments was also assessed using the combined severity factor. Results suggest that thermochemical pretreatment in less severe conditions is the most efficient, leading to a greater increase in methane yield. Only enzymatic pretreatments and some thermal pretreatments result in a positive energy balance. The large-scale implementation of pretreatment methods requires technological innovations to reduce energy consumption and its integration with other processes in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Microalgal biomass–based biofuels are a promising alternative to fossil fuels. Microalgal biofuels' major obstacles are the water and carbon sources for their cultivation and biomass harvest from the liquid medium. To date, an economically viable process is not available for algal based biofuels. The circular bioeconomy is an attractive concept for reuse, reduce, and recycle resources. The recovery of nutrients from waste and effluents by microalgae could significantly impact the escalating demands of energy and nutraceutical source to the growing population. Wastewaters from different sources are enriched with nutrients and carbon, and these resources can be recovered and utilized for the circular bioeconomy approach. However, the utilization of wastewaters and waste seems to be an essential strategy for mass cultivation of microalgae to minimizing freshwater consumption, carbon, nutrients cost, nitrogen, phosphorus removal, and other pollutants loads from wastewater and generating sustainable biomass for value addition for either biofuels or other chemicals. Hence, the amalgamation of wastewater treatment with the mass cultivation of microalgae improved the conventional treatment process and environmental impacts. This review provides complete information on the latest progress and developments of microalgae as potential biocatalyst for the remediation of wastewaters and waste carbon to recover resources through biomass with metabolites for various industrial applications and large-scale cultivation in wastewaters, and future perspectives are discussed. [ABSTRACT FROM AUTHOR]