Emerging trends in the pretreatment of microalgal biomass and recovery of value-added products: A review
Graphical abstract
Introduction
With rapid urbanization and industrialization, the rate of wastewater generation did not match the available wastewater treatment infrastructure and technology, thus leading to the discharge of poorly treated effluent (Mahari et al., 2022). According to Qadir et al. (2020), worldwide 380 trillion L/y of wastewater is generated, with a major contribution from Asian countries (nearly 159 trillion L/y), Europe (68 trillion L/y), and North America (67 trillion L/y). Of this huge amount of wastewater, only 52 % is treated globally and has different treatment rates ranging from low-income (4.3 %) to high-income (74 %) countries (Jones et al., 2021).
Biological wastewater treatments have recently gained significant interest and made much progress due to their sustainable and low-cost approach to treating and recovering resources from various waste streams (Ummalyma and Singh, 2022). Due to its multifaceted benefits, microalgae-based wastewater treatment has been widely explored to treat liquid waste streams and recover nutrients simultaneously. High growth rate, better photosynthesis efficiency, comparative calorific value to fossil fuel, the feasibility of large-scale production, and value-added product development are the key features of microalgae (Goswami et al., 2021, Guldhe et al., 2017). Despite all these desired characteristics, downstream processing of microalgae biomass is energy-intensive, costly, and time-consuming due to the cell’s complex tiny structure and thick cell wall (Phwan et al., 2018). Integrated approaches concerned with microalgae biorefinery targets the fractionation of microalgal biomass into fuel and commercially value-added products through enhanced downstream processing.
Wastewater sourced from industrial, agricultural, dairy, pharmaceutical, and swine contended with high nutrients, is considered a potential medium for microalgal biomass cultivation (Goswami et al., 2021). Microalgae-assisted integrated strategies toward pollutant remediation and value-added product formation by utilizing wastewater are highly promising (Goswami et al., 2021). But selecting appropriate species, optimizing cultivation conditions, and deploying efficient pretreatment methods for cell wall disruption to recover products are key governing factors (Zabed et al., 2020). Costly harvesting and extraction methods with poor product quality are still a challenging issue when applying a biorefinery concept for algal-based wastewater treatment systems (Zhou et al., 2022).
Pretreatment is, thus, recognized as a crucial step in the destruction of complex microalgal cell-wall and the recovery of intracellular products. Mechanical pretreatments such as ultrasonication, high-pressure homogenization, and thermal heating are prominently used for microalgae cell wall destruction (Phwan et al., 2018). In thermochemical pretreatment, the hydrothermal method is considered the most efficient compared to traditional approaches, including acid, microwave, and enzymatic methods (Passos et al., 2016). Microwave (Sirohi et al., 2021), enzymatic (Zhao et al., 2014), fungal (Zhao et al., 2014), and using cationic surfactants like cetylpyridinium chloride, cetylpyridinium bromide, and cetrimonium bromide are also explored as effective pretreatment methods.
Despite several reported microalgae-based wastewater treatment studies, research is still lagging in the direction of comparative assessment of microalgae valorization in different types of wastewater, cost-effective pretreatment strategies, extensive techno-economic analysis (TEA)-life cycle assessment (LCA) of value-added product recovery to find out economic feasibility and environmental sustainability of applied technology. In this direction, the present review provides an enhanced investigation of microalgae-based process integrations for the treatment of different types of wastewater with simultaneous production of commercially valuable products like proteins, lipids, carbohydrates, anti-cancer compounds, and animal feed (Fig. 1). This review critically analyses various conventional and novel pretreatment strategies applied for value-added product recovery from wastewater grown microalgae. Further, critical challenges concerned with pretreatment technologies are discussed based on large-scale applicability, input energy, cost, and recovery efficiency. Techno-economic feasibility analysis for microalgae cultivation in wastewater with value-added product formation is discussed. Thus, the current review highlights the advancements in pretreatment technology associated with microalgae-based biorefinery with in-depth analysis of different kinds of wastewater treatment and value-added product recovery.
Section snippets
Wastewater for microalgal cultivation
Microalgae are explored as a potential feedstock for biofuel production and high-value products with a reduced greenhouse gas footprint. Microalgae culture can be cultivated in three types of modes: photoautotrophic, heterotrophic, and mixotrophic. However, large-scale cultivation requires a large quantity of water and nutrients; thus, wastewater may be considered an inexpensive source to cultivate lipid-rich biomass (see Supplementary material). As a phycoremediation agent, microalgae exhibit
Pretreatment methods for microalgae
Marine or freshwater microalgal species can be grown using different wastewater, and harvested biomass can be used as a source or supplement in foods, feed additives, and raw materials in pharmaceutical and cosmetic industries (Hu et al., 2018, Liaqat et al., 2022). But, the extraction and purification of different valued compounds (i.e., protein, fat, polysaccharides, carotenoid, lutein) from algae are complex and depend on its cell wall composition and structure, which further varies
Polysaccharides
Polysaccharides are one of the major components obtained from microalgae (Table 2), and they are also exploited for their gelation properties in different industrial sectors. Both homo- and heteropolysaccharides can exist as structural, storage, and extracellular polysaccharide (Mendez et al., 2013). However, the occurrence of heteropolysaccharides is predominantly observed with microalgae. The carbohydrate profile generally varies among the species and growth stages of microalgae. Glucose,
Techno-economic analysis of microalgae-based value-added products
Algae-based products are used in different sectors, starting with pharmaceuticals, pigments, chemicals, biofuel, food, and feed additives (Bhatia et al., 2022, Zhang et al., 2021). Interestingly, the United States Foods and Drug Administration considers the variety of algal-based products that are especially used as food and feed additive is generally considered safe. This created a niche market demand for various algal-based products; however, the supply is limited due to various
Challenges and future perspective
Currently, available pretreatment processes have certain drawbacks and can markedly affect the overall production cost. For example, the physical methods currently available are expensive due to high energy input, while the chemicals treatment are either corrosive (due to the use of acids) or result in poor digestibility in the case of alkaline hydrolysis. Small-scale studies on the application of sonication and microwave disruption have been done extensively. But energy input needs to be
Conclusions
Commercialization of algal biorefinery relies on the successful extraction and purification of value-added intracellular products. Approximately 50 % of the cost is used for the pretreatment of algal biomass. The physical pretreatment method is simple but energy-intensive; chemical pretreatment is efficient but generates toxic byproducts. Similarly, biological methods are environmentally friendly but time-consuming; hence ionic liquids or physicochemical-based are becoming more promising but
CRediT authorship contribution statement
Nirakar Pradhan: Writing – original draft, Writing – review & editing, Formal analysis, Resources. Sanjay Kumar: Writing – original draft. Rangabhashiyam Selvasembian: Writing – original draft, Writing – review & editing. Shweta Rawat: Writing – original draft. Agendra Gangwar: Writing – original draft. R. Senthamizh: Writing – original draft. Yuk Kit Yuen: Writing – original draft. Lijun Luo: Writing – original draft. Seenivasan Ayothiraman: Writing – original draft. Ganesh Dattatraya Saratale:
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
This work was supported by the Hong Kong Baptist University with grant numbers: RC-OFSGT2/20-21/SCI/010.
References (138)
- et al.
Natural pigments from microalgae grown in industrial wastewater
Bioresour. Technol.
(2020) - et al.
Bacterial pretreatment of microalgae and the potential of novel nature hydrolytic sources
Environ. Technol. Innov.
(2021) - et al.
Extracellular polysaccharide produced by Chlorella vulgaris–Chemical characterization and anti-asthmatic profile
Int. J. Biol. Macromol.
(2019) Micro-algae as a source of protein
Biotechnol. Adv.
(2007)- et al.
Enhanced productivity of lipid extraction by urea stress conditions on marine microalgae Coelastrum sp. for improved biodiesel production
Bioresour. Technol. Rep.
(2021) - et al.
Biological pretreatments of microalgal biomass for gaseous biofuel production and the potential use of rumen microorganisms: A review
Algal Res.
(2016) - et al.
Pressurized liquid extraction of Neochloris oleoabundans for the recovery of bioactive carotenoids with anti-proliferative activity against human colon cancer cells
Food Res. Int.
(2017) - et al.
A review of microalgae-based biorefineries approach for produced water treatment: Barriers, pretreatments, supplementation, and perspectives
J. Environ. Chem. Eng.
(2022) - et al.
Physical pretreatments of wastewater algae to reduce ash content and improve thermal decomposition characteristics
Bioresour. Technol.
(2014) - et al.
Microalgae biomass from swine wastewater and its conversion to bioenergy
Bioresour. Technol.
(2019)
A critical review on antibiotics and hormones in swine wastewater: Water pollution problems and control approaches
J. Hazard. Mater.
Production of brown algae pyrolysis oils for liquid biofuels depending on the chemical pretreatment methods
Energy Convers. Manag.
Microalgal biomass generation by phycoremediation of dairy industry wastewater: an integrated approach towards sustainable biofuel production
Bioresour. Technol.
Progress in the physicochemical treatment of microalgae biomass for value-added product recovery
Bioresour. Technol.
Microalgal biomass pretreatment for integrated processing into biofuels, food, and feed
Bioresour. Technol.
Integrating bioremediation of textile wastewater with biodiesel production using microalgae (Chlorella vulgaris)
Chemosphere
Hydrolysis of microalgae cell walls for production of reducing sugar and lipid extraction
Bioresour. Technol.
Linking microalgae and cyanobacteria culture conditions and key-enzymes for carbohydrate accumulation
Biotechnol. Adv.
Microalgae-based biorefineries for sustainable resource recovery from wastewater
J. Water Process. Eng.
Prospects, recent advancements and challenges of different wastewater streams for microalgal cultivation
J. Environ. Manage.
Development of a multi-stage continuous fermentation strategy for docosahexaenoic acid production by Schizochytrium sp
Bioresour. Technol.
Application of pulse electric field pretreatment for enhancing lipid extraction from Chlorella pyrenoidosa grown in wastewater
Renew. Energy
Enhanced methane production from microalgal biomass by anaerobic bio-pretreatment
Bioresour. Technol.
Enhanced the energy outcomes from microalgal biomass by the novel biopretreatment
Energy Convers. Manag.
Pressurized liquid extraction with ethanol as a green and efficient technology to lipid extraction of Isochrysis biomass
Bioresour. Technol.
Heterotrophic cultivation of microalgae for pigment production: A review
Biotechnol. Adv.
Physical and chemical pretreatment of lignocellulosic biomass
Valorization of microalgae into 5-hydroxymethylfurfural by two-step conversion with ferric sulfate
J. Environ. Manage.
Insights into the structure-bioactivity relationships of marine sulfated polysaccharides: A review
Food Hydrocoll.
Photoautotrophic organic acid production: Glycolic acid production by microalgal cultivation
Chem. Eng. J.
Modeling and technoeconomic analysis of algae for bioenergy and coproducts
Synergy of biofuel production with waste remediation along with value-added co-products recovery through microalgae cultivation: a review of membrane-integrated green approach
Sci. Total Environ.
Effect of sonication frequency on the disruption of algae
Ultrason. Sonochem.
Historical perspectives on the impact of n-3 and n-6 nutrients on health
Prog. Lipid Res.
Cell disruption and lipid extraction for microalgal biorefineries: A review
Bioresour. Technol.
Development of a pretreatment method based on Fenton-like reaction combined with hydrodynamic cavitation for lipid extraction from wet microalgae
Renew. Energy
Distribution of 21: 6 hydrocarbon and its relationship to 22: 6 fatty acid in algae
Phytochemistry
The lipid biochemistry of eukaryotic algae
Prog. Lipid Res.
Steam explosion as a fractionation step in biofuel production from microalgae
Fuel Process. Technol.
Sulfite-based pretreatment promotes volatile fatty acids production from microalgae: Performance, mechanism, and implication
Bioresour. Technol.
Nutrient removal and lipid production by Coelastrella sp. in anaerobically and aerobically treated swine wastewater
Bioresour. Technol.
Effect of an enzymatic treatment with cellulase and mannanase on the structural properties of Nannochloropsis microalgae
Bioresour. Technol.
Protease cell wall degradation of Chlorella vulgaris: effect on methane production
Bioresour. Technol.
Anticoagulant activity of a sulfated polysaccharide from the green alga Arthrospira platensis
Biochim. Biophys. Acta - Gen. Subj.
Alkali pretreatment method of dairy wastewater based grown Arthrospira platensis for enzymatic degradation and bioethanol production
Fuel
C-phycocyanin extraction assisted by pulsed electric field from Artrosphira platensis
Food Res. Int.
Parametric study of a brewery effluent treatment by microalgae Scenedesmus obliquus
Bioresour. Technol.
Enhancing methane production of Chlorella vulgaris via thermochemical pretreatments
Bioresour. Technol.
Current advances in biological swine wastewater treatment using microalgae-based processes
Bioresour. Technol.
Pretreatment of microalgal biomass for efficient biohydrogen production–Recent insights and future perspectives
Bioresour. Technol.
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