On Aug 14, 2025, Sorour et al. from the Department of Botany and Microbiology, Faculty of Science, Alexandria University, published an article in the journal Scientific Reports entitled "Rhamnolipid from Pseudomonas sp. as a green surfactant for enhanced phytoremediation." The article focuses on the sustainable Microbial Production of Rhamnolipids—a class of valuable glycolipids—and demonstrates their profound efficacy in significantly enhancing the capacity of sunflower plants to clean up soils contaminated with heavy metals like cadmium (Cd) and zinc (Zn). This work establishes a novel, dual-action strategy for efficient and environmentally sound phytoremediation. Rhamnolipids are complex carbohydrate-based amphiphilic molecules, typically featuring one or two L-rhamnose sugar units linked to β-hydroxy fatty acid chains, which grant them exceptional surface-active properties. The ability to produce these high-value specialty carbohydrates from waste streams fundamentally shifts the economic viability of green chemistry solutions for environmental challenges, moving biosurfactants from niche markets toward large-scale industrial use.

Overview

Phytoremediation—the use of plants to clean up environmental pollutants—is widely recognized as a sustainable and aesthetically pleasing alternative to costly, disruptive civil engineering approaches. However, its effectiveness in treating severely contaminated sites is often hampered by the low bioavailability of heavy metals, which are frequently bound tightly within the soil structure. Previous attempts to improve metal uptake using synthetic chemical surfactants introduced secondary pollutants due to poor biodegradability and inherent toxicity. This created an urgent demand for "green" enhancers. Rhamnolipids, as non-toxic, highly effective, and easily biodegradable glycolipid biosurfactants, perfectly address this gap. This study delivers the missing quantitative and molecular data required to transition these promising carbohydrate-based agents from lab curiosity to industrial reality. Historically, biosurfactant research has struggled to compete with synthetic alternatives due to batch-to-batch variability and high production costs. This research provides a crucial counterpoint by demonstrating a robust, waste-stream-fed process. The necessity for non-polluting remediation enhancers is especially acute in agricultural settings where soil health and crop safety are paramount, making the use of a natural, microbially-derived carbohydrate compound vastly preferable to petrochemically sourced alternatives.

Research Results

• Sustainable Glycolipid Manufacturing via Biorefinery

This research successfully engineered a cost-effective and green production route for high-performance biosurfactants. The researchers cultivated Pseudomonas aeruginosa strain ZF2MGHSO (producing Rha1) and Pseudomonas sp. strain AHE16 (producing Rha2) utilizing used vegetable oil as the primary carbon and energy source. This not only addresses waste management but also drastically reduces the feedstock costs associated with traditional carbohydrate manufacturing. Gas chromatography-mass spectrometry (GC-MS) confirmed the high purity and structural integrity of the resulting rhamnolipid glycolipids. Furthermore, the compounds exhibited robust surface activity, including an impressive 80% emulsification index against benzene, confirming their utility as potent surfactant molecules.

Fig.1 GC-MS spectrum of the biosurfactant produced by Pseudomonas sp. strain AHE16. (Sorour, et al., 2025)

• Mobilizing Heavy Metals for Enhanced Bioavailability

The core application of these microbially-derived glycolipids lies in their ability to interact with the soil matrix, enhancing the solubility and mobility of entrenched contaminants. When applied to contaminated soil, both Rha1 and Rha2 significantly increased the concentration of Zn and Cd available for plant uptake. The Rha1 treatment delivered particularly dramatic results, boosting root Zn accumulation to an astounding 724 mg/g DW and root Cd accumulation to 173 mg/g DW. These findings confirm the glycolipids' role as powerful, biodegradable chelating agents that effectively solubilize metal ions, making them biologically accessible to the sunflower plants.

• Glycobiology Mechanism: Upregulation of Metal Transporter Genes

Moving beyond simple chelation, the study provided critical molecular evidence of the synergistic mechanism at play. The team monitored the relative expression levels of the HaZIP1 gene—a known plant transporter involved in Zinc homeostasis—in the roots and shoots of treated plants. Treatment with the Rha1 glycolipid led to a substantial ~6.9-fold upregulation of HaZIP1 expression in the roots and a ~4.8-fold increase in the shoots compared to control plants. This mechanistic insight is groundbreaking, showing that the rhamnolipids not only make the metals available in the soil (extracellular effect) but also trigger the plant's genetic machinery to actively transport the mobilized metals across the cell membrane (intracellular effect).

Fig.2 Relative expression levels of HaZIP1 in roots and shoots of H. annuus plants grown in the experimental soil with two rhamnolipids. (Sorour, et al., 2025)

Conclusion

The combined findings of this paper offer a significant stride forward in both Carbohydrate Manufacturing and environmental remediation. By confirming a sustainable, waste-oil-based production method for high-yield rhamnolipids and definitively proving their dual function—metal mobilization and plant gene activation—the researchers have mapped out a superior, environmentally responsible strategy. Rhamnolipid-enhanced phytoremediation represents an economically feasible and high-performing method for large-scale cleanup of contaminated land, securing the future role of advanced glycolipids as a critical tool in sustainable environmental biotechnology. The commercial implications are substantial: the process achieves the triple bottom line of sustainability, converting waste into a high-value carbohydrate product while simultaneously creating a viable technology for land reclamation. Future research will likely focus on optimizing the rhamnolipid composition (mono- vs. di-rhamnolipids) for maximum efficiency across different soil types and heavy metal profiles. This breakthrough solidifies the position of carbohydrate chemistry as an indispensable pillar in the rapidly expanding field of eco-friendly industrial solutions, promising safer, cleaner environments globally.