Microalgae For Wastewater Treatment Research Articles

Enhancing treatment performance of Chlorella pyrenoidosa on levofloxacin wastewater through microalgae-bacteria consortia: Mechanistic insights using the transcriptome

Microalgae-bacteria consortia (MBC) system has been shown to enhance the efficiency of microalgae in wastewater treatment, yet its effectiveness in treating levofloxacin (LEV) wastewater remains unexplored. This study compared the treatment of LEV wastewater using pure Chlorella pyrenoidosa (PA) and its MBC constructed with activated sludge bacteria. The results showed that MBC improved the removal efficiency of LEV from 3.50–5.41 % to 33.62–57.20 % by enhancing the growth metabolism of microalgae. The MBC increased microalgae biomass and extracellular polymeric substance (EPS) secretion, yet reduced photosynthetic pigment content compared to the PA. At the phylum level, Proteobacteria and Actinobacteriota are the major bacteria in MBC. Furthermore, the transcriptome reveals that the growth-promoting effects of MBC are associated with the up-regulation of genes encoding the glycolysis, the citrate cycle (TCA cycle), and the pentose phosphate pathway. Enhanced carbon fixation, coupled with down-regulation of photosynthetic electron transfer processes, suggests an energy allocation mechanism within MBC. The up-regulation of porphyrin and arachidonic acid metabolism, along with the expression of genes encoding LEV-degrading enzymes, provides evidence of MBC’s superior tolerance to and degradation of LEV. Overall, these findings lead to a better understanding of the underlying mechanisms through which MBC outperforms PA in treating LEV wastewater.

Outdoor tubular photobioreactor microalgae-microorganisms biofilm treatment of municipal wastewater: Enhanced heterotrophic assimilation and synergistic aerobic denitrogenation

This research evaluated a microalgae consortium (MC) in a pilot-scale tubular photobioreactor for municipal wastewater (MWW) treatment, compared with an aeration column photobioreactor. Transitioning from suspended MC to a microalgae-microbial biofilm (MMBF) maintained treatment performance despite increasing influent from 50 L to 150 L in a 260 L system. Carbon and nitrogen removal were effective, but phosphorus removal varied due to biofilm shading and the absence of phosphorus-accumulating organisms. High influent flow caused MMBF detachment due to shear stress. Stabilizing and re-establishing the MMBF showed that a stable phycosphere influenced microbial diversity and interactions, potentially destabilizing the MMBF. Heterotrophic nitrification-aerobic denitrification bacteria were crucial for MC equilibrium. Elevated gene expression related to nitrogen fixation, organic nitrogen metabolism, and nitrate reduction confirmed strong microalgal symbiosis, highlighting MMBF’s treatment potential. This study supports the practical application of microalgae in wastewater treatment.

Calcium Alginate Core–Shell Liquid Beads Encapsulated with Microalgae for Wastewater Treatment

Calcium Alginate Core–Shell Liquid Beads Encapsulated with Microalgae for Wastewater Treatment

Performance evaluation of typical flocculants for efficient harvesting of Chlorella sorokiniana under different carbon application modes

In this study, the growth characteristics of microalgae cultured with different carbon sources were analyzed, and the flocculation characteristics under the influence of carbon sources were evaluated using three typical flocculants. The results showed that the organic carbon sources could significantly increase the content of extracellular proteins in microalgae. Specifically, the extracellular protein concentrations of microalgae cultured with pure BG-11, ethanol, sodium acetate and glucose were 18.2 29.2, 97.3, and 34.7 mg/g, respectively. During the flocculation process, microalgae cultured with sodium acetate exhibited a weak response to the flocculant because of excessive extracellular proteins inhibited flocculation. In addition, the flocculation efficiency was also less than 50.0% cultured with sodium acetate in all pH test ranges when alum and chitosan were used as flocculants. It could be inferred that the flocculant initially happened to charge neutralization with the negatively charged proteins in the solution and then bridged the charges with the microalgae. These findings provide insights into the effects of different carbon sources on microalgal flocculation, promising organic integration of microalgae wastewater treatment and harvesting.

Mixotrophic Chlorella pyrenoidosa biofilm with enhanced biomass production, microalgal activity, and nutrient removal from nutrient-rich wastewater

Microalgae possess significant advantages in nitrogen and phosphorus removal from nutrient-rich wastewater that are highly efficient and independent of the C/N ratio. However, challenges such as low biomass productivity, high variability in nutrient removal under different trophic types, and difficulty in harvesting biomass limits the large-scale application of microalgae wastewater treatment. This study attempted to employ mixotrophic microalgae biofilm to address these issues. The biomass production, microalgal activity, and nutrient removal of Chlorella pyrenoidosa biofilms with different trophic types were compared for nutrient-rich wastewater treatment. The results showed that the biomass productivity of the mixotrophic microalgal biofilm (0.215 g/(L·d)) was 2.3, 8.6, and 6.0 times higher than that of photoautotrophic microalgal biofilm, heterotrophic microalgal biofilm, and photoautotrophic suspended microalga, respectively. Additionally, the dehydrogenase activity (DHA), indicating microalgal activity, of the mixotrophic biofilm was 2.3 and 16.5 times higher than that of photoautotrophic and heterotrophic biofilms, respectively. Meanwhile, the mixotrophic biofilm removed 96.0 % of NH4+-N and 99.2 % of PO43–-P, more efficient than that with other types of biofilms and suspended microalgae. In an open-ended air-lift photobioreactor, the mixotrophic microalgal biofilm produced biomass at 0.12 g/(L·d) and removed 90.0 % of NH4+-N and 97.6 % of PO43–-P. This study suggests that the mixotrophic microalgal biofilm shows promise in treating nutrient-rich wastewater and producing microalgal biomass for value-added products.

Influence of Hydrogen induction on performance and emission characteristics of an agricultural diesel engine fuelled with cultured Scenedesmus obliquus from industrial waste

The use of microalgae in waste water treatment has been recognised as crucial for managing and treating effluent from industrial sources. Present study used Scenedesmus obliquus (SO) strains in industrial waste cultured medium, grown algae were collected and dried, further with dried mass to algae bio fuel by transesterification process. Four fuel blends were created by adjusting the SO concentration from 10% to 40% by volume. Then SO blend was examined with impact of hydrogen induction on compression ignition engine. The addition of H2 to SO biodiesel enhances its net calorific value because of its high calorific content.Adding H2-inducted SO proportion to diesel reduces HC, NOx, and CO levels, with a negligible performance dip. At full loads, SO40 showed a significant improvement in emission levels, with a 19.81% reduction in NOx, a 51 ppm drop in HC and 1.146% dropobserved in CO compared to diesel. For the SO10 mix, BTE and BSEC were found to be 2.86% and 2103.77 kJ/kW-hr, respectively, superior to other SO blends. Subsequently, it is of crucial significance to acknowledge the significance of the potential those microalgaeprovides for the production of sustainable energy through the reprocessing of industrial effluents.

Calcium Alginate Core–Shell Liquid Beads Encapsulated with Microalgae for Wastewater Treatment

Liquid beads are core–shell particles with a liquid core and a solid shell. Calcium alginate liquid beads have been emerging as a promising platform for cell encapsulation. These beads have demonstrated their capability of encapsulating and culturing a wide range of human cells for tissue engineering. However, a significant research gap remains in the application of alginate liquid beads for encapsulating photosynthetic microorganisms. Herein, fast‐growing microalgae strain Chlorella vulgaris is encapsulated into calcium alginate liquid beads to facilitate the removal of nutrients from wastewater, minimizing the risk of eutrophication. Liquid bead‐microalgae systems are prepared, using different calcium ion concentrations as crosslinking ions. It has been thoroughly characterized for their morphologies, cell growth patterns, nutrient removal capabilities, and overall stability throughout the wastewater treatment process, with upflow anaerobic sludge blanket effluent as the wastewater model. The results indicate that the liquid bead‐microalgae system with the highest calcium ion concentration (5%) performs more efficiently, exhibiting a well‐formed crosslinking structure, leading to rapid cell growth with the highest cell density and the most effective removal of nutrients. The findings from this study provide valuable insights for future optimization and upscaling efforts in wastewater treatment systems based on calcium alginate liquid beads.

Reduction in environmental hazards and enhance the energy conversion from microalgae wastewater: Characteristics evaluation

AbstractThe formation of algae blooms can influence uncontrolled growth, causing hazards to aquatic ecosystems. The attention of microalgae wastewater treatment is gathering significance in bio‐energy conversion, resulting in environmental sustainability. Gasification technology is found to improve energy conversion with improved environmental sustainability. The novel research is to treat microalgae wastewater via hydrothermal gasification process with the assistance of a potassium hydroxide catalyst (KOH). During the gasification process, the gasification time is varied from 10, 20, and 30 min under a higher gasification temperature of 900°C is maintained throughout the gasification process. Effect of gasification processing time with KOH catalyst action on the percentage of molar fractions including carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2) and methane (CH4), lower heating value (LHV), syngas H2 yield, and gasification efficiency of hydrothermal gasification process for microalgae wastewater are experimentally investigated. The results of the present investigation are exposed with higher processing time with maximum gasification temperature processed with KOH catalyst offered maximum H2 fraction of 59%, reduced CH4 and LHV of 15% and 10 MJ/Nm3, optimum H2 yield of 22 mol/kg, and attained maximum gasification efficiency of 55%, respectively. The optimum gasification process parameters, including a 30‐min processing time with a higher gasification temperature of 900°C gained H2, will be suggested for energy/alternative fuel applications.

Assessing the effect of Fe2O3 nanoparticle addition on microalgae wastewater treatment and biomass composition

The addition of Fe2O3 nanoparticles to microalgae cultures has gained popularity since it has been demonstrated to enhance microalgae growth and metabolite accumulation. However, most of the literature has been focused on small batch laboratory-scale studies under controlled conditions and the need of continuous studies under real environmental conditions is needed to demonstrate the feasibility of this process. In this study, the effect of Fe2O3 nanoparticles on the metabolism and nutrient uptake of a microalgae-cyanobacteria consortium cultivated in wastewater was elucidated. Different concentrations of Fe2O3 nanoparticles (10, 20, 30 and 70 mg L−1) were assessed at least for 21 days in outdoor cylindrical PBRs at 7 days of hydraulic retention time. No significant difference in microalgae growth, microalgae biomass composition and nutrient uptake was observed at concentrations <30 mg L−1. Moreover, when 30 mg L−1 were added to the culture, the carbohydrate content increased up to 38 % but a decrement in biomass concentration of 18 % was observed by the deposition of nanoparticles on the cyanobacteria cell wall. The addition of 70 mg Fe2O3 L−1 reduced the content of carbohydrate and biomass concentration but did not influence the nutrient uptake from wastewater. In brief, Fe2O3 NP supplementation at 30 mg L−1 can be added as a strategy to stimulate carbohydrate content during microalgae-based wastewater treatment.

Application of algae in wastewater treatment

Nowadays, water contamination has become one of the most significant environmental issues. The creation and use of algal biotechnology with less investment, good effect and low operating cost has garnered a lot of attention. With the ongoing development of numerous new water treatment technologies, low-cost and effective ecological governance systems have been created quickly. Its purpose is to improve the sewage purification process by improving the inorganic process of organic matter, accelerating the expansion and multiplication of microorganisms, enhancing the metabolic function of microorganisms, and promoting the proliferation of microorganisms. In this article, the removal of nitrogen, phosphorus, heavy metals, antibiotics, pathogens and pesticides by algae was introduced. Additionally, typical algae systems including immobilized algae systems, algal-bacterial symbiotic systems and combination high-rate algae pond systems used in sewage treatment and the limitations and prospects of algae technology were discussed. Algal wastewater treatment is more effective in removing nitrogen and phosphorus than conventional activated sludge processes. Aquaculture wastewater, industrial drainage, municipal sewage, and other distinct forms of water treatment processes can all benefit from the simultaneous transformation and removal of nitrogen, phosphorus, sulfur, refractory organic matter, and heavy metals in sewage that is made possible by algae technology. Engineering techniques and technological advancement will be used to create high-efficiency microalgae wastewater treatment reactors, optimize conditions, increase the utilization efficiency of microalgae biological resources, and apply microalgae to wastewater treatment, which will have a significant impact on water quality and economy.

Enhancing biochar structure and removal efficiency of ammonium and microalgae in wastewater treatment through combined biological and thermal treatments

This study explored the efficiency of biological pre-treatment combined with thermal treatment to produce biochars, called E-biochars, for the removal of ammonium and microalgae without using chemical pre-treatment. The aim was to develop an environmentally sustainable approach for large-scale biochar production with high efficiency in wastewater treatment. The biological pre-treatment involved incubating the sawdust with Bacillus subtilis for 14 to 20 days and then subjected to pre-treatment at low temperatures (250-350 °C). This process broke down cellulose and altered its lignocellulosic structure, improving the biochar's morphology by leading to a more anisotropic pore structure. The thermal pre-treatment after that will help to open a broader range of pore sizes, spanning from macropores to micro-pores in the 1 μm to 5 μm dimension range. These alterations facilitated the efficient removal of ammonium and microalgae during adsorption experiments. The findings fit the Langmuir and the Freundlich models, according to the isotherm test of NH4+ and microalgae (R2 = 0.92÷0.99). The E-biochar termed EBH20, composted with Bacillus subtilis for 20 days at 350 °C, performed best, with Qmax equal to 40.2 mg/ g NH4+ under neutral conditions (pH = 7). Interestingly, the co-occurrence of ammonium and microalgae enhanced the removal of these contaminants. The interaction between microalgae cells and ammonium facilitated ammonium adsorption onto biochar and microalgae. The column breakthrough curves under NH4+ and NH4+ mixed microalgae adsorption were predicted using the Thomas model with the high agreement (R2 = 0.91÷0.99) for ammonium but for algae between prediction and running experimental column data.

Variation of the photosynthesis and respiration response of filamentous algae (Oedogonium) acclimated to averaged seasonal temperatures and light exposure levels

Filamentous algae (FA) have potential advantages over microalgae for wastewater treatment. However, their implementation at a large-scale is hindered by an inability to predict performance. This study compared the cellular responses (photosynthesis and respiration) and composition (pigments and photosystem proteins) of FA Oedogonium acclimatised to average summer and winter conditions (Melbourne, Australia). After seven days of acclimation the Chl a content of ‘summer acclimated’ (SA) algae was about half that of the ‘winter acclimated’ (WA) algae, which can be related to a cellular strategy to reduce photodamage under high light intensities. No statistically significant changes were observed in any identified proteins associated with photosystem PSII and the reaction centre of PSI. Transmission electron microscopy images revealed more prominent lipid bodies within the SA filaments than in WA filaments, but no discernible difference in the abundance of starch granules.Photosynthetic irradiance curves were compared for the SA and WA algae. Consistent with the differences in chlorophyll, the specific gross photosynthetic rate (μP, gross) was generally higher for the WA algae. The relative difference increased from around 2-fold at 15 °C to 3-fold at 25 °C, and then decreased to <1.5-fold at 30 °C and 35 °C. At all the tested temperatures, saturation irradiance levels were in the range of 75–500 μmol/m2·s. Photoinhibition was observed at 30 °C (above ∼300 μmol/m2·s) and was more severe at 35 °C (above ∼500 μmol/m2·s), with WA algae showing greater inhibition. In contrast, the respiration response was similar for the SA and WA algae. The study emphasises the significance of accounting for seasonal variations and their effects on biomass productivity and utilisation. The data obtained will enable the incorporation of acclimation and its effect on biochemistry and photosynthetic response into predictive models of FA performance in outdoor cultures.

Phenol phycoremediation by Haematococcus pluvialis coupled with enhanced astaxanthin and lipid production under rac-GR24 supplementation for enhanced biodiesel production

The present study evaluated the impact of rac-GR24 on biomass and astaxanthin production under phenol stress coupled with biodiesel recovery from Haematococcus pluvialis. Phenol supplementation showed negative impact on growth, where the lowest biomass productivity of 0.027 g L-1 day−1 was recorded at 10 µM phenol, while 0.4 µM rac-GR24 supplementation showed the highest recorded biomass productivity of 0.063 g L-1 day−1. Coupling 0.4 µM rac-GR24 at different phenol concentrations confirmed the potential of rac-GR24 to mitigate the toxic effect of phenol by enhancing yield of PSII yield, RuBISCo activity, and antioxidant efficiency, which resulted in improved phenol phycoremediation efficiency. In addition, results suggested a synergistic action by rac-GR24 supplementation under phenol treatment where rac-GR24 enhanced lipid accumulation, while phenol enhanced astaxanthin production. Dual supplementation of rac-GR24 and phenol showed the highest recorded FAMEs content, which was 32.6% higher than the control, with improved biodiesel quality. The suggested approach could enhance the economic feasibility of triple-purpose application of microalgae in wastewater treatment, astaxanthin recovery, and biodiesel production.

Municipal Wastewater Effects on the Performance of Nutrient Removal, and Lipid, Carbohydrate, and Protein Productivity of Blue-Green Algae Chroococcus turgidus

The use of microalgae in wastewater treatment (WWT) is seen as a promising and sustainable alternative to conventional WWTs, and the obtained biomass is gaining importance as a bio-product. The present study aimed to investigate the effectiveness of using municipal wastewater (MWW) as a nutritional supplement for the cultivation of the cyanobacteria Chroococcus turgidus (Kützing) Nägeli 1849 and the pollutant removal potential of the microalgae. The WW received from the different treatment stages (primary, secondary, and final effluent) was applied to the microalgae culture, and algal growth was compared with regard to growth rate, nutrient removal efficiency, and final algal lipid (%) and protein (%) content. In 7-day batch experiments, except for BOD5 analysis, COD, PO4-P, and N forms analyses were carried out daily in parallel with in vivo Chl-a and Chl-b, DO, pH, temperature, and conductivity measurements. The growth rates and Chl-a quotas of the microalgae grown in trials were different, and the highest growth rate was with a 1.03 ± 0.06 d−1 in the primary effluent (PE). The highest Chl-a and Chl-b quotas among WW trials of microalgae were obtained from the PE trial as 252.4 ± 2 µg L−1 and 112 ± 18 µgL−1, respectively. NH4-N, NO3-N, NO2-N, PO4-P, BOD5, and COD treatment efficiencies were in the ranges of (74.6–83%), (16–71.2%), (22.2–63.6%), (89–95.3%), (50–76.2%), and (70.3–78.6%), respectively. The microalgae were observed to accumulate the highest lipid (28.05 ± 2.26%DW) content in secondary effluent (SE), the highest carbohydrate (43.93 ± 1.02%DW) content in the effluent (E), and the highest protein content (35.25 ± 1.22%DW) in the PE. The results of this study suggested that C. turgidus is a new candidate for bioremediate pollution load of MWW, and its biomass has the potential to offer options in bio-product applications.

Sub-pilot scale cultivation of Tetradesmus dimorphus in wastewater for biomass production and nutrients removal: Effects of photoperiod, CO2 concentration and aeration intensity

The potential of microalgae in wastewater treatment and resource utilization has received considerable interest. For better outcomes in large-scale cultivations, it is usually essential to optimize the microalgal culture parameters in a sub-pilot cultivation system. Herein, a series of experiments were carried out to investigate the effects of photoperiod, CO2 concentration and aeration intensity on nutrients removal and biomass production of Tetradesmus dimorphus under the 50 L culture scale. The results showed that the removal rates of chemical oxygen demand (CODcr), NH4+-N and total phosphorus (TP) in primary effluent (PE) were 93.9 %, 92.3 % and 84.8 %, respectively. Compared with 15 h:9 h (15 h light and 9 h dark cycle), the maximum Chlorophyll-a content of 2797.78 mg/m3 was reached at 24 h:0 h. The maximum microalgae biomass (OD680 = 0.56) was obtained when the CO2 concentration was 200 mL/min, but CO2 enrichment inhibited nitrogen removal. At optimal aeration intensity (60 L/h), the highest chlorophyll-a content was recorded on day 3. The removal rates of NH4+-N and TP were 92.1 % and 89.7 %, respectively.

Life cycle assessment of microalgae systems for wastewater treatment and bioproducts recovery: Natural pigments, biofertilizer and biogas

The aim of this study was to assess the potential environmental impacts associated with microalgae systems for wastewater treatment and bioproducts recovery. In this sense, a Life Cycle Assessment was carried out evaluating two systems treating i) urban wastewater and ii) industrial wastewater (from a food industry), with the recovery of bioproducts (i.e. natural pigments and biofertilizer) and bioenergy (i.e. biogas). Additionally, both alternatives were compared to iii) a conventional system using a standard growth medium for microalgae cultivation in order to show the potential benefits of using wastewater compared to typical cultivation approaches. The results indicated that the system treating industrial wastewater with unialgal culture had lower environmental impacts than the system treating urban wastewater with mixed cultures. Bioproducts recovery from microalgae wastewater treatment systems can reduce the environmental impacts up to 5 times compared to a conventional system using a standard growth medium. This was mainly due to the lower chemicals consumption for microalgae cultivation. Food-industry effluent showed to be the most promising scenario for bioproducts recovery from microalgae treating wastewater, because of its better quality compared to urban wastewater which also allows the cultivation of a single microalgae species. In conclusion, microalgae wastewater treatment systems are a promising solution not only for wastewater treatment but also to boost the circular bioeconomy in the water sector through microalgae-based product recovery.

Enhancement of black and odorous water treatment coupled with accelerated lipid production by microalgae exposed to 12C6+ heavy-ion beam irradiation

In this study, Auxenochlorella protothecoides (AP-CK) was selected due to its reported high growth potential in sterilized black and odorous water (SBOW). In order to improve the resource utilization level of microalgae for wastewater treatment, AP-CK was mutated using 12C6+ heavy-ion beam irradiation, and a high lipid-containing mutant (AP-34#) was isolated and further evaluated to treat original black and odorous water (OBOW). Compared with the wild type, the maximum removal rates of COD, NH4+-N and TP of the mutant increased by 8.12 ± 0.33%, 10.43 ± 0.54% and 11.97 ± 0.16%, respectively, while maximum dissolved oxygen content increased from 0 to 4.36 ± 0.25 mg/L. Besides, the mutant lipid yield increased by 115.87 ± 3.22% over the wild type in OBOW. The fatty acid profile of AP-34# grown in SBOW and OBOW showed higher proportion of saturated fatty acids (C16:0 and C18:0) and valuable polyunsaturated fatty acids (mainly C20:5n3 and C22:6n3) which are more suitable for biodiesel production and value-added products, respectively. This work provides a new perspective on improving the characteristics of microalgae and an innovative approach for resource-based microalgae wastewater treatment through bioremediation of black and odorous water.

Monitoring PHB production in Synechocystis sp. with hyperspectral images.

Microalgae wastewater treatment systems have the potential for producing added-value products. More specifically, cyanobacteria are able to accumulate polyhydroxybutyrates (PHBs), which can be extracted and used for bioplastics production. Nonetheless, PHB production requires proper culture conditions and continue monitoring, challenging the state-of-the-art technologies. The aim of this study was to investigate the application of hyperspectral technologies to monitor cyanobacteria population growth and PHB production. We have established a ground-breaking measurement method able to discern spectral reflectance changes from light emitted to cyanobacteria in different phases. All in all, enabling to distinguish between cyanobacteria growth phase and PHB accumulation phase. Furthermore, first tests of classification algorithms used for machine learning and image recognition technologies had been applied to automatically recognize the different cyanobacteria species from a complex microbial community containing cyanobacteria and microalgae cultivated in pilot-scale photobioreactors (PBRs). We have defined three main indicators for monitoring PHB production: (i) cyanobacteria specific-strain density, (ii) differentiate between growth and PHB-accumulation and (iii) chlorosis progression. The results presented in this study represent an interesting alternative for traditional measurements in cyanobacteria PHB production and its application in pilot-scale PBRs. Although not directly determining the amount of PHB production, they would give insights on the undergoing processes.

Production of Biofertilizer from Industrial Waste Water by Microalgal Treatment

Due to rapid industrialization and the depletion of non-renewable fossil fuels, alternative feasible renewable alternatives are being sought to supply rising energy demand while reducing carbon dioxide emissions. Microalgae cultivation has the to meet these criteria in today's world energy strategy, which is centred on cost-effective and environmentally friendly alternatives. Microalgae has been discovered as a promising and long-term solution for wastewater treatment and the generation of valuable products. Microalgae, which have a short life cycle, a rapid growth rate, and a high CO2 usage efficiency, are one of the most feasible renewable resource technologies for producing biomass from wastewater nutrients. Technology and cost are now the key issues limiting industrial-scale use, which necessitates an optimum downstream process to reduce manufacturing costs. These issues have become feasible and economically viable thanks to the utilisation of microalgae for wastewater treatment and biofuel generation at the same time. The efficacy of microalgae for the removal of ammonia, phosphorus, and heavy metals, as well as the creation of biofuel and biofertilizer, is examined. It also aims to concentrate on current breakthroughs in wastewater microalgae growth, as well as the response of microalgae to various stimuli and their implications on the quality and quantity of high-value products.

Microalgal Biorefinery Concepts' Developments for Biofuel and Bioproducts: Current Perspective and Bottlenecks.

Microalgae have received much interest as a biofuel feedstock. However, the economic feasibility of biofuel production from microalgae does not satisfy capital investors. Apart from the biofuels, it is necessary to produce high-value co-products from microalgae fraction to satisfy the economic aspects of microalgae biorefinery. In addition, microalgae-based wastewater treatment is considered as an alternative for the conventional wastewater treatment in terms of energy consumption, which is suitable for microalgae biorefinery approaches. The energy consumption of a microalgae wastewater treatment system (0.2 kW/h/m3) was reduced 10 times when compared to the conventional wastewater treatment system (to 2 kW/h/m3). Microalgae are rich in various biomolecules such as carbohydrates, proteins, lipids, pigments, vitamins, and antioxidants; all these valuable products can be utilized by nutritional, pharmaceutical, and cosmetic industries. There are several bottlenecks associated with microalgae biorefinery. Hence, it is essential to promote the sustainability of microalgal biorefinery with innovative ideas to produce biofuel with high-value products. This review attempted to bring out the trends and promising solutions to realize microalgal production of multiple products at an industrial scale. New perspectives and current challenges are discussed for the development of algal biorefinery concepts.