Microalgae and Cyanobacteria: How Exploiting These Microbial Resources Can Address the Underlying Challenges Related to Food Sources and Sustainable Agriculture: A Review

For thousands of years, crop production has almost entirely depended on conventional agriculture. However, the reality is changing. The ever-growing population, global climate change, soil degradation and biotic/abiotic stresses are a growing threat to food production and security. Thus, sustainable alternatives to increase crop production for a population projected to reach 9.8 billion by 2050 are a major priority. In addition to vertical and soilless farming, innovative products based on bioresources, including plant growth stimulants, have been a target for sustainable food production. Such solutions have led to the exploitation of microorganisms, including microalgae and cyanobacteria as potential bioresources for food and plant biostimulant products. Microalgae (eukaryotic) and cyanobacteria (prokaryotic) are photosynthetic microorganisms with the capacity to synthesize a vast array of bioactive metabolites from atmospheric CO2 and inorganic nutrients. The present review outlines the nutritional value of microalgae and cyanobacteria as alternative food resources. The potential aspects of microalgae and cyanobacteria as stabilizers of the net change in soil organic carbon (C) levels for reduced farmland degradation are also highlighted. The applications of microalgae and cyanobacteria as remedies for improved soil structure and fertility, and as enhancers of crop productivity and abiotic stress tolerance in agricultural settings are outlined. This review also discusses the co-cultivation of crops with microalgae or cyanobacteria in hydroponic systems to favor optimum root CO2/O-2 levels for optimized crop production.