Microalgae as a sustainable source of edible proteins and bioactive peptides - Current trends and future prospects

The global demand for protein ingredients is continuously increasing owing to the growing population, rising incomes, increased urbanization, and aging population. Conventionally, animal-derived products (dairy, egg, and meat) satisfy the major dietary protein requirements of humans. With the global population set to reach 9.6 billion by 2050, there would be a huge deficit in meeting dietary protein requirements. Therefore, it is necessary to identify sustainable alternative protein sources that could complement high-quality animal proteins. In recent years, microalgae have been advocated as a potential industrial source of edible proteins owing to their wide and excellent ecological adaptation. Microalgae can grow in marginal areas utilizing non-potable wastewaters with high photosynthetic efficiency. Previously microalgae species such as Arthospira, and Chlorella have been used as single-cell proteins (SCP) with limited application in pharmaceutical industries. In recent years, the demand for innovative and sustainable functional ingredients for food applications has renewed the interest worldwide in microalgae proteins. The present review aims to provide a holistic view of various aspects related to the production and processing of edible proteins from microalgae biomass. A critical review of available literature on the nutritional quality, techno-functional properties, applications in food and feed sectors, and biological activities is presented. Further, challenges associated with each stage of processing are discussed. From the literature review, it can be summarized that microalgae proteins are comparable to reference proteins both in terms of amino acid (AA) quality and techno-functional properties. However recalcitrant cell wall poses a challenge in digestibility and effective utilization of the microalgae proteins. Further, poor sensory scores and palatability of microalgae biomass limit its applications in the food and feed sector. Novel applications of microalgae proteins include meat analogues, emulsifying agents, and bioactive peptides. Development of low-cost cultivation strategies, wet biomass-based downstream processing along with the bio-refinery approach of complete biomass volarization would enhance the sustainability quotient for human food applications.