Unlocking the Functional and Nutritional Potential of Microalgae Proteins in Food Systems: A Narrative Review

Microalgae encompass a phylogenetically diverse group of unicellular, photosynthetic organisms that thrive in a wide variety of aquatic environments. This diversity includes prokaryotic cyanobacteria (such as Spirulina) and eukaryotic taxa like chlorophytes (e.g., Chlorella vulgaris), diatoms (e.g., Phaeodactylum tricornutum), and eustigmatophytes (e.g., Nannochloropsis) [8]. These microalgae differ widely in morphology, pigment content, growth characteristics, and metabolite production, enabling diverse applications in food and biotechnology.

Biochemically, many microalgal species exhibit high protein contents, ranging from 40% to 70% of dry biomass, making them highly competitive with conventional protein sources like soy or animal products [16]. The amino acid composition is often well-balanced, with many species providing all the essential amino acids necessary for human nutrition [17]. Genetic variability among species, along with external factors such as light intensity, salinity, pH, and nutrient availability, significantly influences protein yields and composition [18].

Furthermore, microalgae produce valuable bioactive compounds including polyunsaturated fatty acids, antioxidants (e.g., astaxanthin, β-carotene), vitamins (B12, E), and minerals (iron, magnesium), further increasing their appeal as functional ingredients [4,19]. For instance, Haematococcus pluvialis and Dunaliella salina are confirmed as the leading microalgae for the commercial production of astaxanthin and β-carotene, respectively, with astaxanthin reaching up to 7% and β-carotene up to 13% of dry weight [20].

The nutritional profile of microalgae proteins is increasingly well-documented. Proteins from species such as Spirulina and Chlorella exhibit high digestibility and excellent amino acid profiles, with PDCAAS and Digestible Indispensable Amino Acid Scores (DIAAS) often comparable to conventional protein sources [14]. These proteins support muscle synthesis, metabolic regulation, and tissue repair, making them ideal for use in general nutrition and sports recovery formulas. In addition to macronutrients, microalgae provide a rich profile of micronutrients and bioactive compounds. Spirulina is an exceptional source of iron and B-complex vitamins, especially of B12 in a form potentially bioavailable to humans [11], while Chlorella is noted for its chlorophyll and antioxidant contents [9]. Moreover, many microalgae contain omega-3 fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), offering a plant-based alternative to fish oils [21].

Hydrolysis of microalgae proteins can release peptides with biological activities. In vitro and in silico studies have shown that peptides derived from Chlorella and Spirulina can act as inhibitors of digestive enzymes such as α-amylase and α-glucosidase, making them promising for managing blood glucose and metabolic syndrome [17]. Other studies suggest that these peptides also possess antihypertensive, anti-inflammatory, and immunomodulatory effects [22], indicating a strong potential for future functional food and nutraceutical development.

Equally important are the functional properties of microalgae proteins, which enhance their value as food ingredients. Their amphiphilic structure allows microalgae proteins to act as effective emulsifiers, foaming agents, and gelling agents across diverse pH and temperature conditions [23]. For instance, Spirulina-based proteins have been used in dairy-free spreads and beverages to provide smooth textures and enhance stability, while Chlorella proteins support structure and gelation in meat analogues and baked products.

Pigmented microalgae such as Haematococcus and Dunaliella also provide natural colourants (e.g., astaxanthin and β-carotene), which can improve product aesthetics and support clean-label formulation strategies [24]. The multifunctional role of microalgae, providing both nutritional enhancement and techno-functional performance, streamlines ingredient lists and meets growing consumer preferences for natural, minimally processed foods.

Moreover, microalgae show promise in improving the sensory and structural attributes of food. In gluten-free bread, the inclusion of microalgae like Nannochloropsis and Chlamydomonas improved the protein content and textural quality while increasing micronutrient density and antioxidant capacity [25]. These functional advantages open new doors for microalgae in baking, dairy substitutes, snacks, and meat analogues.

Table 1 consolidates data across major microalgae species used in food systems. It compares protein content, essential amino acid balance, presence of bioactive compounds, and functional traits such as solubility, emulsification, and gelation. For instance, Spirulina is characterised by a high protein content and excellent foaming capacity, while Chlorella vulgaris provides a well-rounded amino acid profile and gelation support. Nannochloropsis offers a strong profile in omega-3 fatty acids, whereas Haematococcus pluvialis is a source of the potent antioxidant astaxanthin. This integration serves as a practical tool for food technologists and researchers, enabling the rapid assessment of microalgae species for specific product applications. Importantly, cultivation parameters and downstream processing techniques can be fine-tuned to further enhance desired traits such as pigment concentration or peptide bioactivity [26].

Microalgal proteins are located intracellularly, necessitating effective cell wall disruption for extraction. The complexity and rigidity of microalgae cell walls vary across species, influencing the required extraction technique. For example, Chlorella vulgaris has a particularly tough, cellulose-rich wall, while Spirulina lacks a conventional cellulose wall, allowing for easier extraction [70].

Mechanical disruption methods remain among the most widely used for breaking these barriers. High-pressure homogenization subjects microalgal biomass to extreme shear forces, rupturing cell walls but potentially denaturing sensitive proteins due to friction-induced heat. Ultrasonication, another common method, employs high-frequency sound waves to generate cavitation bubbles that physically disrupt cells. Although it reduces thermal damage compared to homogenization, it requires careful energy control to prevent localised overheating [71].

Emerging non-thermal approaches like pulsed electric field (PEF) treatment offer a more protein-friendly solution. PEF applies short high-voltage bursts to induce electroporation, forming temporary pores in the cell membrane. This allows intracellular proteins to diffuse out with minimal structural degradation, particularly useful for preserving heat-sensitive fractions [72].

Enzymatic lysis represents a complementary or alternative approach. By targeting specific cell wall components using cellulases, proteases, or lysozymes, enzymatic treatments offer a selective and mild strategy to extract proteins while minimising energy input and protein denaturation [73,74]. When paired with mechanical disruption, enzymatic treatment enhances extraction efficiency and protein integrity [75,76].

Following extraction, purification is essential to isolate the protein fraction and remove unwanted components such as pigments, lipids, and carbohydrates. One of the most accessible methods is isoelectric precipitation, where proteins are precipitated at their isoelectric point (pI), the pH at which their net charge is zero. This technique allows for bulk protein recovery, especially in species with well-characterised pI values [77].

Membrane-based technologies such as ultrafiltration and diafiltration are widely used in continuous production environments. These techniques separate molecules based on size, concentrating proteins while removing small molecular weight impurities like salts or pigments. Their scalability and chemical-free nature make them attractive for food-grade applications [78].

For applications requiring highly pure protein fractions, chromatographic methods such as ion exchange, affinity, and size-exclusion chromatography can be employed. These are particularly effective for isolating bioactive proteins, like phycocyanin from Spirulina, or low-molecular-weight peptides with specific functionalities [75]. However, their resource and cost intensity may limit industrial-scale adoption unless integrated efficiently.

Once isolated, proteins can be further modified to enhance functional properties such as solubility, emulsification, foaming, or bioactivity. Among these, enzymatic hydrolysis is one of the most promising. Controlled treatment with proteases like Alcalase or Trypsin cleaves specific peptide bonds, reducing molecular weight and exposing functional groups. These modifications increase digestibility and often produce peptides with antioxidant or antihypertensive activity [62].

For example, hydrolysates from Scenedesmus obliquus prepared using optimised Alcalase–Trypsin treatment showed an excellent emulsifying and fat-binding capacity, especially for peptides under 10 kDa [62]. Similarly, Chlorella-derived peptides under 3 kDa produced using ultrasound-assisted enzymatic hydrolysis demonstrated both ACE-inhibitory and antioxidant activity, highlighting their dual nutritional and functional roles [79].

In addition to hydrolysis, pH shifting (exposing proteins to extreme acidic or alkaline conditions) can be used to unfold and refold protein structures, enhancing solubility and gelation. Thermal treatments, if carefully controlled, can expose hydrophobic regions that improve the emulsifying capacity without causing aggregation or loss of functionality [77].

Cross-linking techniques, whether enzymatic (e.g., transglutaminase) or physical (e.g., high-pressure processing), can further tailor the texture and network-forming abilities of proteins. This is particularly useful in applications such as plant-based meat or dairy analogues, where gelling and water retention are critical [75].

Each processing step, from cell disruption to final modification, directly impacts the techno-functional and nutritional properties of the protein product. Overly aggressive mechanical treatment may yield high protein recovery but result in denaturation that reduces solubility and bioactivity. In contrast, a mild enzymatic treatment may produce a lower yield but result in peptides with superior emulsification, digestibility, and health benefits [71].

The ability to selectively enhance certain functionalities, such as improving foaming for whipped toppings or boosting solubility for beverages, through controlled processing is one of the key advantages of microalgal proteins. This flexibility supports their use in a wide variety of formulations, from sports nutrition to dairy alternatives, clean-label sauces, and even functional snacks [62].

In summary, the ability to integrate and optimise cell disruption, extraction, purification, and protein modification techniques is vital to unlocking the potential of microalgae as sustainable protein sources. These strategies must strike a careful balance between maximising recovery and preserving the molecular characteristics responsible for desirable nutritional and functional properties. Continued innovations in non-thermal, enzymatic, and eco-friendly approaches will be essential in making microalgae proteins competitive in the growing market for alternative and functional protein ingredients.

Microalgae proteins hold significant potential as functional ingredients in the development of dairy alternatives such as plant-based yoghurts, milks, cheeses, and probiotic beverages. Their complete amino acid profiles, high digestibility, and excellent emulsifying and water-holding capacities allow them to replicate the structural and textural roles of bovine milk proteins, making them well-suited for dairy-mimetic formulations [80]. For example, proteins from species like Spirulina and Chlorella have been shown to stabilise emulsions and improve mouthfeel in plant-based milks, while also contributing valuable micronutrients such as vitamin B12 and iron [21].

In fermented dairy alternatives, microalgae proteins enhance both functional and nutritional attributes. Chlorella vulgaris and Pavlova lutheri, when incorporated into yoghurt-like products, have been reported to boost antioxidant activity, increase mineral bioavailability (e.g., iron and magnesium), and positively influence sensory qualities such as colour and flavour [81]. In addition, fermentation may improve the release and bioaccessibility of microalgae-derived nutrients, contributing to enhanced functional properties [18].

Recent studies also suggest that the fermentation of microalgae-enriched matrices can enhance protein digestibility and release bioactive peptides with antihypertensive or antioxidant activity, supporting their role in functional fermented foods [22]. These multifunctional traits make microalgae proteins promising candidates for formulating the next generation of clean-label, plant-based dairy alternatives tailored for both health benefits and consumer acceptance.

The bakery industry is another area where microalgae proteins are being actively explored. For instance, Chlorella vulgaris has been used to replace 100% of animal-based fat and protein in brioche-type baked goods without compromising texture or flavour, and in some cases improving them [82]. Microalgae proteins enhance dough elasticity, improve moisture retention, and extend shelf life, making them a valuable functional addition in both traditional and gluten-free formulations.

In pasta and noodles, the incorporation of microalgae proteins contributes not only to the protein content but also to cooking stability and firmness. Fortified pasta enriched with Spirulina or Chlorella exhibits higher levels of micronutrients such as iron and vitamin B12, and retains an appealing texture during cooking [6].

Extruded snack products also benefit from the structure-forming and water-binding abilities of microalgae proteins. Their integration into cereals, crackers, and chips results in snacks with enhanced crispness and protein density, while also contributing antioxidant and anti-inflammatory benefits [83].

One of the most exciting areas of application is 3D food printing, where rheological control and structural stability are critical. Microalgae proteins enhance batter printability, helping maintain shape fidelity and texture in extrusion-based printing systems. Research has shown that snacks enriched with 3–5% Chlorella or Spirulina maintain structural accuracy and show improved nutritional value [84].

Although higher concentrations may affect sensory appeal due to strong pigmentation, emerging technologies such as coaxial printing are being explored to mask colour while preserving nutritional value. This opens pathways for personalised nutrition, where microalgae can be tailored to create meals that target specific dietary needs.

Microalgae proteins are also being used in functional beverages and plant-based smoothies. Their high solubility and complete amino acid content make them ideal for sports recovery drinks, senior nutrition supplements, and high-performance wellness beverages. When combined with fruits or plant milks, microalgae proteins contribute not only to protein content but also to antioxidant capacity and micronutrient delivery [18].

Beyond conventional food applications, microalgae proteins are increasingly incorporated into functional foods and nutraceutical products. Enzymatic hydrolysis of these proteins yields bioactive peptides with significant health benefits, including antihypertensive, antioxidant, anti-inflammatory, and cholesterol-lowering effects [85]. These peptides can be used in dietary supplements and fortified foods aimed at managing chronic diseases, particularly cardiovascular conditions.

Peptides derived from Spirulina and Chlorella have demonstrated ACE-inhibiting activity, a target in hypertension management. Their integration into capsule, powder, or beverage forms enables flexible delivery platforms in health and wellness markets [10].

Many species of microalgae, such as Haematococcus pluvialis and Dunaliella salina, produce highly pigmented compounds like astaxanthin and β-carotene. These pigments serve dual purposes: they act as natural antioxidants and provide a vibrant colour that enhances product appeal [24]. With the rising consumer demand for clean-label products, replacing synthetic dyes with microalgae-derived pigments offers a valuable marketing and health advantage.

Applications include natural food colourants in beverages, confections, yoghurts, and sauces. The added nutritional benefits make them a multifunctional solution for food developers looking to combine aesthetics and health.

The integration of microalgae proteins into food systems spans both traditional and emerging formats, demonstrating their multifunctionality and future potential (see Table 1). From improving dough structure in baked goods to supporting muscle recovery in drinks, or even building structural frameworks in 3D-printed snacks, microalgae proteins are pushing the boundaries of food innovation. Their clean-label credentials, functional health benefits, and environmental sustainability make them well-positioned to play a major role in the next generation of food products. Continued advances in cultivation, processing, and sensory optimisation will further expand their utility across mainstream and specialised food markets.

Figure 1 illustrates the relative extent to which key microalgae species are utilised in various food applications, including dairy alternatives, baked goods, meat analogues, snacks, functional beverages, and 3D-printed foods. These proportions reflect both reported functional suitability and prevalence in the literature.

Microalgae are widely recognised as one of the most promising sustainable protein sources due to their low land footprint, high productivity, and capacity to thrive in conditions unsuitable for conventional agriculture. They can be cultivated on non-arable or marginal lands using saline or brackish water, significantly reducing dependence on freshwater and eliminating competition with food crops [86].

Microalgae also offer substantial environmental benefits through their rapid growth cycles and high photosynthetic efficiency, allowing for exceptional areal productivity. Many species double their biomass within 24–48 h, far outpacing terrestrial crops in growth rates and yield per hectare [87]. Moreover, their photosynthetic mechanism enables the direct capture and conversion of carbon dioxide into biomass, contributing to greenhouse gas mitigation and aligning with global decarbonization goals [88].

An especially impactful application lies in coupling microalgae cultivation with wastewater treatment. Industrial and municipal effluents, rich in nitrogen and phosphorus, can be repurposed as nutrient sources, thus eliminating the need for synthetic fertilisers while reducing the ecological burden of wastewater discharge [89]. This approach turns waste into a valuable input, exemplifying circular bioeconomy principles and supporting closed-loop production models [90]. However, it is important to note that the use of biomass grown on such substrates for human or animal consumption is subject to strict regulatory scrutiny. While promising from an environmental standpoint, such applications currently face significant legislative hurdles and are typically limited to non-food uses unless thorough safety validation is performed.

Additionally, microalgae cultivation integrates well with flue gas recycling from industrial sources, providing a dual benefit of carbon sequestration and biomass generation. Some pilot projects have demonstrated reductions in net CO₂ emissions of over 50% when flue gases are used as a carbon input for microalgal growth [91].

Despite their potential, the transition from laboratory-scale to commercial-scale microalgae production is fraught with technical and operational challenges. Open raceway ponds, though cost-effective, are highly susceptible to contamination, evaporation, and environmental fluctuations that can disrupt growth and reduce protein yields. They also offer limited control over nutrient delivery and pH stabilisation, which are essential for producing consistent biomass quality [87].

In contrast, closed photobioreactors (PBRs) provide better control over temperature, CO₂ levels, and contamination, resulting in higher biomass and protein quality. However, PBRs involve significantly higher capital and operating costs, often requiring energy-intensive lighting, mixing, and CO₂ regulation. Hybrid systems, combining the scalability of open ponds with the precision of PBRs, are being explored as a potential compromise [92].

Another critical barrier is the harvesting process. Techniques such as centrifugation are effective but energy-intensive and costly, while flocculation, though more affordable, raises concerns regarding the safety of chemical additives for food or feed applications. Regulatory frameworks may restrict the use of certain flocculants unless proven to be food-grade or used in closed-loop systems. As the reviewer noted, biomass produced via fermentation may offer a more controlled and compliant route for human and animal nutrition. These factors must be carefully considered when designing scalable and compliant harvesting strategies.

One major bottleneck in scalability is the biomass variability resulting from external factors such as light intensity, nutrient availability, and water chemistry. This inconsistency affects downstream processes like extraction, purification, and formulation. To mitigate this, real-time monitoring technologies using machine learning, sensor networks, and automated feedback systems are being adopted to ensure optimal growth conditions and standardise output quality [91].

Furthermore, genetic engineering and strain improvement strategies hold promise for enhancing protein yields and resistance to environmental stressors. Selective breeding and CRISPR-based editing can lead to strains with improved uniformity, enabling more predictable scaling and efficient downstream processing [86].

Achieving economic viability remains one of the biggest hurdles for commercial microalgae protein production. High production and processing costs continue to limit scalability, especially when microalgae are treated as single-output systems. As a solution, the integrated biorefinery model is gaining traction, an approach that enables the recovery of multiple co-products from a single biomass input.

For example, while protein may be the primary target, high-value pigments like phycocyanin from Spirulina and astaxanthin from Haematococcus can generate substantial revenue in the nutraceutical and cosmetic markets [24]. Lipid fractions containing omega-3 fatty acids can also be purified for food and feed, while residual biomass may be converted into biofertilizers or biochar, completing the resource loop [89].

Integrating renewable energy sources such as solar thermal or photovoltaic systems into cultivation operations can significantly lower energy inputs. Automation, such as AI-based light modulation or nutrient dosing, also reduces labour and enhances reproducibility, contributing to long-term economic resilience [90].

Finally, regulatory frameworks and market acceptance play a crucial role in economic viability. Harmonised safety and labelling standards will reduce barriers to entry, while educational campaigns about the nutritional and ecological benefits of microalgae can accelerate consumer uptake, especially in high-growth markets for plant-based and functional foods [85]. For example, Spirulina and Tetraselmis chui have received Generally Recognised As Safe (GRAS) status in the US and Novel Food approval in the EU.

Microalgae proteins represent a promising, sustainable, and innovative solution for the global protein crisis. Their potential to be cultivated on non-arable land using waste streams while simultaneously capturing carbon dioxide places them at the forefront of environmentally responsible food technologies. However, achieving large-scale adoption requires addressing several technical and economic bottlenecks. Integrated biorefineries, automation, genetic optimisation, and hybrid cultivation systems are paving the way toward commercial viability.

No new data were created or analysed in this study. Data sharing is not applicable to this article.