Process development of enzymatically-generated algal protein hydrolysates for specialty food applications

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

As the global demand for sustainable, nutrient-rich protein sources intensifies, microalgae have emerged as a promising alternative due to their unique biochemical, environmental, and functional properties. This narrative review synthesises the nutritional value, protein composition, functional behaviour, processing technologies, and food applications of microalgae proteins. A literature search was conducted using PubMed, Scopus, and Web of Science, with keywords including "microalgae proteins", "nutritional value", "functional properties", and "alternative protein sources". Priority was given to peer-reviewed articles from the past decade that addressed nutritional quality, extraction methods, and food applications. Key species, Spirulina, Chlorella, Nannochloropsis, and Haematococcus, are highlighted for their high protein content (up to 70% dry weight), complete amino acid profiles, and rich bioactive compound content. Microalgae proteins show excellent solubility, emulsification, gelation, and foaming abilities, enabling use in dairy alternatives, baked goods, snacks, and 3D-printed foods. Advances in extraction, purification, and protein modification have improved their functionality, while cultivation on non-arable land and integration into circular biorefineries enhance sustainability. Remaining challenges include scalability, sensory optimisation, and regulatory clarity. Future studies should focus on improving sensory acceptance, optimising cost-effective processing, and expanding consumer awareness. Overall, microalgae proteins offer a robust and eco-efficient solution to meet global nutrition and sustainability goals.

Methods to protein and peptide extraction from microalgae: a systematic review

Currently, there is a demand for protein sources that do not use soil management or animal breeding. Among these sources we highlight the microorganisms, such cyanobacteria and microalgae, which have a simple growth using light, CO2, water and some mineral salts to generate high protein production. The extraction of these proteins depends on the method used. The most used methods for extracting bio-functional proteins are mechanical, chemical and enzymatic. The aim of this work is to analyze the protein extraction methods in microalgae using Scielo, ScienceDirect and NCBI (PubMed) electronic databases that made it possible to select original studies published in the last five years (2018-2023). A total of 2707 articles, 25 of which were selected for further analysis and subjected to risk of bias assessment. The genera Chlorella, Scenedesmus and Nannochloropsis were the most studied due to their high protein content. Mechanical methods and chemical hydrolysis are the most used methods, achieving an extraction yield of 46.0 % and 64.0 %, respectively. The best extraction results are obtained with a combination of methods, reaching up to 80.0 % yield. However, some aspects need to be observed to choose an ideal protein extraction method.

Microalgal proteins: Unveiling sustainable alternatives to address the protein challenge

Recent breakthroughs emphasized the considerable potential of microalgae as a sustainable protein source. Microalgae are regarded as a substitute for protein-rich foods because of their high protein and amino acid content. However, despite their nutritional value, microalgae cannot be easily digested by humans due to the presence of cell walls. In the subsequent sections, protein extraction technology, the overview of the inherent challenges of the process, and the summary of the factors affecting protein extraction and utilization have been deliberated. Moreover, the review inspected the formation of proteolytic products, highlighting their diverse bioactivities, including antioxidant, antihypertensive, and immunomodulatory activities. Finally, the discussion extended to the emerging microalgal protein sourced foods, such as baked goods and nutritional supplements, as well as the sensory and marketing challenges encountered in the production of microalgal protein foods. The lack of consumer awareness about the health benefits of microalgae complicates its acceptance in the market. Long-standing challenges, such as high production costs, persist. Currently, multi-product utilization strategies are being developed to improve the economic viability of microalgae. By integrating economic, environmental, and social factors, microalgae protein can be sustainably developed to provide a reliable source of raw materials for the future food industry.

Recent developments and challenges in algal protein and peptide extraction strategies, functional and technological properties, bioaccessibility, and commercial applications

The burgeoning demand for protein, exacerbated by population growth and recent disruptions in the food supply chain, has prompted a rapid exploration of sustainable protein alternatives. Among these alternatives, algae stand out for their environmental benefits, rapid growth, and rich protein content. However, the widespread adoption of algae-derived proteins faces significant challenges. These include issues related to harvesting, safety, scalability, high cost, standardization, commercialization, and regulatory hurdles. Particularly daunting is the efficient extraction of algal proteins, as their resilient cell walls contain approximately 70% of the protein content, with conventional methods accessing only a fraction of this. Overcoming this challenge necessitates the development of cost-effective, scalable, and environmentally friendly cell disruption techniques capable of breaking down these rigid cell walls, often laden with viscous polysaccharides. Various approaches, including physical, chemical, and enzymatic methods, offer potential solutions, albeit with varying efficacy depending on the specific algal strain and energy transfer efficiency. Moreover, there remains a pressing need for further research to elucidate the functional, technological, and bioaccessible properties of algal proteins and peptides, along with exploring their diverse commercial applications. Despite these obstacles, algae hold considerable promise as a sustainable protein source, offering a pathway to meet the escalating nutritional demands of a growing global population. This review highlights the nutritional, technological, and functional aspects of algal proteins and peptides while underscoring the challenges hindering their widespread adoption. It emphasizes the critical importance of establishing a sustainable trajectory for food production, with algae playing a pivotal role in this endeavor.

Influence of magnesium concentrations on the biomass and biochemical variations in the freshwater algae, Chlorella vulgaris

The current study deals with the biological response variations on some biochemical properties of the freshwater green algae Chlorella vulgaris by exposure to different Mg²⁺ concentrations (5, 10, and 15) mg/L. Physiological and biochemical parameters, including growth curve, doubling time, photosynthesis pigments, total protein and carbohydrates were investigated. Moreover, enzymatic parameters such as catalase (CAT), superoxide dismutase (SOD), and reactive oxygen species (ROS) were also examined. The maximum growth rate was 0.482/day during the 9th day with 5 mg/L Mg²⁺, while the minimum was 0.019/day during the 13th and 14th days with 10 mg/L Mg²⁺. Furthermore, doubling time ranged between 15.501 during the 13th day with 10 mg/L Mg²⁺, and 0.624 during the 9th day with 5 mg/L. The maximum value of chlorophyll-a was 0.157 μg/mL during the 1st day with 10 mg/L Mg²⁺, while the minimum was 0.062 μg/mL during the 14th day with 15 mg/L Mg²⁺. The carotenoid ranged between 0.029 μg/mL during the 7th day with 15 mg/L Mg²⁺ and 0.002 μg/mL during the 14th day. The maximum protein value was 9.620 μg/L during the 1st day with 15 mg/L Mg²⁺, while the minimum was 1.772 μg/L during the 14th day with 15 mg/L Mg²⁺. The carbohydrate showed a maximum value of 0.824 μg/mL during the 1st day with 10 mg/L Mg²⁺, while the minimum was 0.293 μg/mL during the 14th day with 15 mg/L. Moreover, SOD ranged between 0.884 unit/L during the 1st day with 15 mg/L Mg²⁺, and 0.073 unit/L as the minimum value during the 14th day with 15 mg/L Mg²⁺. The maximum value of ROS was 3.627 mM/mL during the 1st day with 5 and 15 mg/L Mg²⁺, while the minimum was 1.674 mM/mL during the 14th day with 10 mg/L. The results show that values of CAT ranged between 0.200 unit/mL during the 7th day with 10 mg/L Mg²⁺, and 0.010 unit/mL during the 14th day with 15 mg/L. Overall, 5 mg/L for biomass production and 15 mg/L for protein and carbohydrate production were optimum doses.

Feasibility of membrane ultrafiltration as a single-step clarification and fractionation of microalgal protein hydrolysates

Protein hydrolysates are one of the most valuable products that can be obtained from lipid-extracted microalgae (LEA). The advantages of protein hydrolysates over other protein products encompass enhanced solubility, digestibility, and potential bioactivity. The development of an economically feasible process to produce protein hydrolysates depends on maximizing the recovery of hydrolyzed native protein from the lipid-extracted algal biomass and subsequent fractionation of hydrolyzed protein slurry. Previously, we reported a method for fractionation of enzymatically generated protein hydrolysates by acidic precipitation of algal cell debris and unhydrolyzed protein, precipitate wash, centrifugation, and depth filtration. The present study evaluates tangential flow ultrafiltration as a single-step alternative to centrifugation, precipitate wash, and depth filtration. The results demonstrate that the tangential flow ultrafiltration process has a potential that deserves further investigation. First, the membrane diafiltration process uses a single and easily scalable unit operation (tangential flow filtration) to separate and “wash out” hydrolyzed protein from the algal residue. Second, the protein recovery yield achieved with the tangential flow process was >70% compared to 64% previously achieved by centrifugation and depth filtration methods. Finally, protein hydrolysates obtained by membrane ultrafiltration exhibited slightly better heat and pH stability.