Molecular Soil Biology 2026, Vol.17, No.1, 1-11 http://bioscipublisher.com/index.php/msb 8 Figure 8 Changes in carbohydrate content of microalgae SA-2 Note: (a) Standard curve for carbohydrate content; (b) treatment groups with different concentrations of EDTA-Ca; (c) treatment groups with different concentrations of EDTA-Fe. Different lowercase letters indicate a significant difference(P<0.05) The chelating effect of EDTA plays a key role in microalgal cultivation. By binding Fe3+ andCa2+, EDTA prevents the rapid precipitation of these metal ions in the medium, thereby maintaining their bioavailability and extending their effective period in the culture. EDTA not only facilitates the uptake of metal ions but also indirectly regulates metabolic processes, improving light energy utilization and carbon flux allocation. Chelation of Fe by EDTA ensures the normal synthesis of key cellular components, such as iron–sulfur proteins and cytochromes, enhancing electron transport efficiency and promoting accumulation of photosynthetic products. Proper levels of EDTA-Ca help stabilize cell structure and regulate transmembrane ion channels, thereby improving overall cellular homeostasis. These positive effects synergistically enable higher growth rates and biomass production, with the presence of EDTA being a critical prerequisite for the promotive effects of both elements. EDTA’s chelation satisfies the continuous demand for metal ions during metabolic processes. Microalgae, as microorganisms with high light energy utilization efficiency and short growth cycles (Zhou and Ruan, 2014), hold significant potential in sustainable energy and biofuel production, the production of high-value nutrients and food additives, environmental remediation and carbon neutrality, as well as agriculture and fertilizer applications. Their further potential remains to be explored. This study systematically investigated the differential effects of EDTA-chelated metal ions (Fe and Ca) on microalgal biomass accumulation, providing new insights into strategies for enhancing biomass production. By referring to domestic and international reports on microalgal physiological responses to stress and the role of metal chelators in plants and algae, this study analyzed the effects of EDTA-Fe and EDTA-Ca on microalgal growth characteristics, cell viability, and biomass components including proteins, lipids, pigments, and carbohydrates. It was found that appropriate concentrations of EDTA-Fe and EDTA-Ca promoted the accumulation of various biomasses and cell biomass in SA-2, whereas excessive concentrations inhibited both biomass content and cell growth. These findings provide a theoretical basis for effective micronutrient supplementation strategies in microalgal cultivation. Future studies could further explore the synergistic effects of combined EDTA-Fe and EDTA-Ca supplementation, and, based on the specific metabolic characteristics of target algal species, develop customized chelated micronutrient nutrition schemes. Such approaches could enable integrated strategies for EDTA-Fe and EDTA-Ca supplementation in large-scale algal cultivation systems, improving biomass yield and the concurrent accumulation of high-value products such as lipids, polysaccharides, or pigments. With further process optimization and ecological safety evaluation, these findings are expected to advance the application of microalgae in biofuels, carbon mitigation, and bioproduct development. 4 Materials and Methods 4.1 Materials The microalga Nannochloris sp. SA-2 used in this study was isolated from saline-alkaline soil in Anda City, Heilongjiang Province, and was previously identified and preserved in our laboratory. It was cultured in Bold’s Basal Medium (BBM) under shaking conditions at 100 r/min. The cultivation temperature was maintained at (23±1) ℃, with a light/dark photoperiod of 16 h:8 h and a light intensity of 2 000 lx.
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