Influence of Different Extraction Solvents and the Micronutrient Composition on the Bioactive Properties and Antimicrobial Efficacy of Spirulina Maxima Extracts

Abstract

Spirulina is a highly valued, nutrient-rich, blue-green alga and is recognized for its high protein content, as well as for its functional food components such as vitamins, amino acids, minerals, and antioxidants, with potential benefits for immune health. The growing recognition of Spirulina’s nutritional and health-promoting properties has contributed to its rising demand as a functional food ingredient. The present study aimed to evaluate the influence of different extraction solvents and the micronutrient composition on the bioactive properties and antimicrobial efficacy of Spirulina maxima extracts. In the current study, S. maxima was successively extracted based on solvent polarity, and each extract was identified by TLC analysis. The micronutrient content of the powdered sample was determined using an Atomic Absorption Spectrophotometer (AAS). Fe (2.43 mg/g) and Cu (0.72 mg/g) were the predominant micronutrients, while Ni and Cd were not detected in the raw powdered sample. High-Performance Liquid Chromatography (HPLC) was used to identify and estimate Phycocyanin. The antimicrobial activity for both the extract and phycocyanin against Gram-positive and Gram-negative bacteria — Pseudomonas aeruginosa (ATCC 15692), Staphylococcus aureus (ATCC 23235), Bacillus subtilis (ATCC 15245), Klebsiella pneumoniae (ATCC 700603), and Escherichia coli (ATCC 25922) — was evaluated using the agar diffusion method, and the results were compared with those of the standard Gentamicin (50 μg/mL). The serial dilution method was used to determine the Minimum Inhibitory Concentration (MIC) of the S. maxima extract, using Gentamicin as the positive control. The ethanolic extract exhibited the highest activity, and the MIC values ranged from 16.8 to 146.7 μg/mL. The findings highlight S. maxima as a promising natural source of bioactive compounds, where solvent polarity and micronutrient composition significantly contribute to its antimicrobial potential.