Bio‐Based Sodium Alginate Beads Reinforced With Microalgae ( Limnospira platensis ): Structure–Property Relationships and Controlled Release Potential

ABSTRACT

Agricultural productivity depends on efficient nutrient management, currently dominated by synthetic inorganic fertilizers. Considering the projected depletion of phosphate reserves within the next five decades, sustainable alternatives are increasingly required. Biopolymer‐based matrices have emerged as promising systems for controlled nutrient release, potentially mitigating leaching losses. In this study, sodium alginate (SA) beads incorporating microalgal biomass ( Limnospira platensis ) were produced via Ca ⁺² mediated ionic crosslinking to investigate how biomass incorporation influences the physicochemical behavior of the polymeric network. The composite systems were characterized by TGA, SEM, and FTIR‐ATR to evaluate structural and thermal properties. Swelling degree, aqueous degradation, soil biodegradability, and nitrogen and phosphorus release were analyzed. Microalgal incorporation modified the swelling behavior and degradation profile of the alginate matrix, and formulations incorporating microalgal biomass at 1% and 2% (w/v) exhibited enhanced water retention and gradual nutrient diffusion. These findings highlight the role of bio‐based fillers in modulating the architecture and performance of ionically crosslinked alginate networks, suggesting potential applicability in controlled nutrient delivery systems.