Cyanobacteria and microalgae represent promising sources for sustainable production of biofertilizers and biostimulants, which can improve crop yield and quality and contribute to food security. However, despite their potential, their exploration remains incomplete, hindered by technical and economic challenges that arise when attempting to scale up production. The primary focus of this review is to delve into the active chemical compounds responsible for the biofertilizing and biostimulating roles of cyanobacteria and microalgae. In addition, it explores the essential unit operations involved in transforming their biomass into potential bioproducts. Moreover, this review highlights studies that have employed cyanobacteria and microalgae as sources of biofertilizer in various crops, describing their mode of action and application. By integrating cyanobacteria and microalgae processing with other advanced biotechnological, the viability of these products for sustainable agriculture can be significantly enhanced.

The continued increase in human populations and use of chemical fertilizers remain a threat to the health and stability of human–ecological systems worldwide. To ameliorate this problem and achieve long-term food security, a variety of ecofriendly technologies have been developed, including the production of cyanobacteria-based biofertilizers. This technology can be optimized through experiments that assess how plant growth is enhanced under different biofertilizer concentrations (g L⁻¹). In this study, the biofertilizer capabilities of various concentrations of sonicated biomass (0, 2.5, 5, 10, 20, and 40 g L⁻¹) derived from the cyanobacteria Arthrospira maxima on the growth of basil (Ocimum basilicum, Lamiaceae) were assessed, comparing their effectiveness with that of a positive control, a commercial biofertilizer (OptiMar Algas Marinas^®) administered at 4 mL L⁻¹. Generally, increased concentrations led to enhanced growth parameters; however, discernible differences from the negative control (0 g L⁻¹) were often observed only when concentrations exceeded 5 g L⁻¹. Surprisingly, the negative and positive controls often yielded similar results. A chemical composition analysis of A. maxima revealed high concentrations of the phytohormones, macronutrients, and essential amino acids that likely explain how our A. maxima sample enhanced growth in basil. Further research is required to determine how other crop plants respond to different concentrations of A. maxima. Additionally, assessing the feasibility of creating an economically accessible product with a higher concentration of A. maxima is crucial for practical applications.

Continued increase of human populations and use of chemical fertilizers remain a threat to the health and stability of human-ecological systems worldwide. To ameliorate this problem and achieve sustainable agriculture, a variety of ecofriendly technologies have been developed, including the production of cyanobacteria-based biofertilizers. This technology can be optimized through experiments that assess how plant growth is enhanced under different biofertilizer concentrations (g L^− 1). Here we assess the biofertilizer potential of hydrolysates derived from the cyanobacteria Arthospira maxima on the growth of basil (Ocimum basilicum) under six different concentrations (0, 2.5, 5, 10, 20, and 40 g L^− 1), and an additional treatment where we applied the registered product Optimar ® (4 mL L^− 1). For all response variables except stem length, a concentration of 40 g L^− 1 yielded significantly higher values. The beneficial effects of the application of Optimar were often surpassed when plants received cyanobacteria concentrations above 10 g L^− 1. A chemical composition analysis of A. maxima revealed high concentrations of the phytohormones gibberellic acid (0.19 g L^− 1), 6-benzyladenine (0.37 g L^− 1), and 1-naphthaleneacetic acid (0.25 g L^− 1) that are likely responsible for the cyanobacteria’s biostimulant activity. Further research is required to determine how other crop plants respond to different concentrations of A. maxima and the viability of creating an economically accessible product with a higher concentration of A. maxima using circular economy and biorefinery concepts to obtain high value-added by-products.