Identifying Antimicrobial Agents from Chlorella sorokiniana: A Biotechnological Approach Utilizing Eco-Friendly...

It was already known that natural compounds offer a significantly reduced environmental footprint compared to their synthetic counterparts in various industrial and pharmaceutical applications. Conventional extraction methodologies frequently utilize hazardous chemicals such as chloroform or hexane, which contribute significantly to ecological degradation and persistent chemical pollution. These traditional processes often require extreme temperatures or high pressures to isolate secondary metabolites from complex biological matrices, leading to high energy consumption. While microalgae represent a vast and diverse reservoir of functional molecules with potent biological activities, the reliance on toxic solvents undermines the overall sustainability of their commercial exploitation. Existing protocols for characterizing these organisms typically prioritize the total mass yield over the environmental safety or the long-term toxicity of the reagents employed. The lack of standardized green chemistry protocols for microalgal processing hinders the transition toward a truly circular bioeconomy. This absence of evidence motivated the search for sustainable chemical alternatives that maintain high recovery rates without compromising ecological integrity or human health.

This investigation established an eco-friendly extraction framework to isolate and characterize antimicrobial agents from the autotrophic microalga Chlorella sorokiniana (C. sorokiniana). The researchers sought to determine if sustainable chemical alternatives like dimethyl carbonate (DMC) could effectively replace chloroform in the recovery of bioactive fractions. A primary objective involved assessing how sodium hydroxide (NaOH) pre-treatment influences the total yield and the subsequent biological potency of extracted substances from the biomass. The team aimed to quantify the inhibitory effects of these extracts against specific bacterial pathogens including Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). By comparing green solvents with traditional non-green options, the study intended to validate a more responsible approach to bioprospecting within the field of phycology. The work focused on identifying specific molecular correlations between the chemical composition of the extracts and their observed antimicrobial efficacy. This research aimed to provide a scalable model for the sustainable production of natural antibiotics from renewable aquatic resources.

The experimental design utilized Dimethyl Carbonate (DMC), Methoxycyclopentane (CPME), and Butan-2-one (MEK) as environmentally responsible solvents for biomass processing. Chloroform served as the non-green reference standard to benchmark the efficiency and selectivity of these sustainable chemical alternatives. Investigators applied Sodium Hydroxide (NaOH) to pre-treat the microalgae biomass, comparing these results against untreated samples to evaluate the necessity of cell wall disruption. Antimicrobial potency was measured using Minimum Inhibitory Concentration (MIC) assays against Escherichia coli (E. coli), Bacillus megaterium (B. megaterium), and Bacillus subtilis (B. subtilis). Chemical profiling of the resulting extracts was performed via Gas Chromatography-Mass Spectrometry (GC-MS) to identify specific bioactive constituents and volatile metabolites. Statistical validation involved Principal Component Analysis (PCA) to map complex correlations between molecular profiles and the degree of pathogen inhibition. Analysis of Variance (ANOVA) and post hoc tests (p < 0.05) ensured the statistical significance of findings regarding solvent selection and the impact of pre-treatment on yield.

Extraction using Butan-2-one (MEK) achieved the highest recovery rate among the tested solvents, reaching a yield of 182 ± 27 milligrams per gram of dry weight (mg/g DW). Untreated microalgae biomass consistently yielded extracts with superior antimicrobial efficacy compared to those derived from pre-treated samples, suggesting that alkaline conditions may degrade sensitive bioactive molecules. The most potent inhibitory effect occurred with the Methoxycyclopentane (CPME) extract from untreated biomass, which recorded a Minimum Inhibitory Concentration (MIC) of 4.89 ± 0.05 micrograms per milliliter (µg/mL) against Escherichia coli (E. coli). This performance closely approached the efficacy of the vancomycin control, which exhibited an MIC of 1.55 ± 0.03 µg/mL under identical experimental conditions. Principal Component Analysis (PCA) successfully linked specific compounds identified through Gas Chromatography-Mass Spectrometry (GC-MS) to the observed biological activity against Gram-positive and Gram-negative bacteria.

These findings demonstrate that green solvents represent viable and sustainable alternatives for the recovery of bioactive molecules from autotrophic microalgae like Chlorella sorokiniana (C. sorokiniana). The study confirms that Dimethyl Carbonate (DMC) and Methoxycyclopentane (CPME) can effectively replace hazardous chemicals in biotechnological workflows without sacrificing antimicrobial potency. Utilizing untreated biomass appears to preserve the integrity of antimicrobial compounds more effectively than alkaline pre-treatment methods, which may simplify future industrial processing steps. This research provides a foundation for developing large-scale, eco-friendly processes in the pharmaceutical and nutraceutical industries seeking natural alternatives to synthetic preservatives. Future efforts should focus on optimizing these green extraction parameters for other microalgal species to broaden the library of natural antibiotics available for clinical use. The integration of sustainable chemistry into microalgal bioprospecting significantly reduces the environmental burden of drug discovery and aligns with global sustainability goals.