Phenanthrene is a three-ring polycyclic aromatic hydrocarbon used in the study as a representative petroleum contaminant. Its hydrophobic structure limits its availability to microorganisms, while its persistence and toxicity make its removal environmentally important. Bacteria from several genera have been reported to degrade petroleum hydrocarbons, including Achromobacter, Acinetobacter, Bacillus, Marinobacter, Micrococcus, Pseudomonas and Rhodococcus. Many bioremediation experiments use agitated or well-aerated cultures, but the researchers selected static conditions to test whether degradation could occur without continuous mixing. Under those conditions, VITSVK4 degraded phenanthrene without an externally imposed aeration or agitation regime.

The researchers obtained soil from a depth of 5–10 cm in the Vallimalai hills near Katpadi, Vellore, India, after removing the exposed surface layer. They enriched the sample for seven days in Bushnell Haas broth containing 100 mg/L phenanthrene as the sole carbon source, keeping the cultures static throughout. Two isolates with distinct colony morphologies, designated VITSVK4 and VITSVK5, were selected. Both formed biofilms, and a 96-well assay classified both as strong producers. In the initial comparison, VITSVK4 degraded 45% ± 2.08% of 100 mg/L phenanthrene over seven days, compared with 29% ± 1.73% for VITSVK5. VITSVK4 also produced stronger biosurfactant activity, with an emulsification index of 73% ± 2.30%, compared with 62% ± 2.08% for VITSVK5.

Additional screening showed positive lipase and laccase activity for VITSVK4, whereas VITSVK5 was positive only in the lipase assay. Researchers therefore selected VITSVK4 for molecular characterization and the detailed degradation experiments. They amplified and sequenced a 1,418-base-pair segment of the isolate’s 16S rRNA gene. A BLASTN comparison with 100% query coverage showed 99.44% sequence similarity to a reference S. maltophilia strain, supporting the tentative identification. The gene sequence was deposited in GenBank under accession PX485663, and phylogenetic analysis was used to assess its relationship to reference sequences.

Growth measurements showed that dry biomass increased progressively during a 10-day experiment in medium containing phenanthrene and 0.3% yeast extract. It reached a maximum of 0.74 ± 0.05 g/L on day eight and declined over the following days. One-factor-at-a-time testing examined temperature, pH, inoculum volume and incubation time under static conditions. Among the levels tested, 32 °C, pH 7, a 2% inoculum and an eight-day incubation produced the highest phenanthrene degradation. Yeast extract was the most effective nitrogen-containing supplement among those tested. In a separate supplementation experiment, 0.3% yeast extract yielded 66% ± 2.3% degradation, higher than the values obtained with the other nitrogen sources evaluated.

Under the selected laboratory conditions, VITSVK4 achieved its highest measured removal of phenanthrene at an initial concentration of 100 mg/L: 72% ± 1.73% after eight days. Removal decreased as the starting concentration rose, although the strain still degraded 59.3% ± 2.08% at 500 mg/L under static conditions over the same eight-day period. A pronounced decline began at concentrations of 600 mg/L and above. These percentages describe losses of the parent compound from the test medium after extraction and comparison with abiotic controls; they do not represent a uniform degradation rate across soils, sediments or mixed petroleum contaminants.

Gas chromatography–mass spectrometry provided chemical evidence consistent with removal of phenanthrene. The uninoculated control produced a prominent chromatographic peak at a retention time of 15.20 minutes, corresponding to phenanthrene, whereas the degraded culture had no detectable peak at that retention time. The researchers also identified a limitation in the extraction procedure: hexane is poorly suited to recovering polar and acidic phenanthrene transformation products. The chromatogram therefore supports disappearance of the parent compound from the extractable fraction, but it does not identify the complete transformation pathway, establish the extent of mineralization or demonstrate that every resulting product is environmentally safe.

Seed-germination experiments indicated that treatment with VITSVK4 reduced the phytotoxicity associated with phenanthrene. In mung bean, Vigna radiata, 90% of seeds germinated in liquid treated with VITSVK4, compared with 10% in untreated phenanthrene and 100% in distilled water. Estimated phytotoxicity was 24.5% for treated phenanthrene and 94.7% for untreated phenanthrene. In wheat, Triticum aestivum, 70% of seeds germinated in the treated material, compared with no germination in untreated phenanthrene and 90% in distilled water. The treated wheat had estimated phytotoxicity of 13.1%. Treated mung-bean roots and wheat shoots and roots did not differ significantly from their distilled-water controls, whereas treated mung-bean shoots were significantly shorter than the water control. These measurements apply to the two tested plant species and the laboratory exposure conditions used in the assay.

In additional screening assays, VITSVK4 degraded benzene, toluene and xylene, as well as phenol, mineral oil, crude oil and used engine oil. The strain’s cell-free supernatant showed biosurfactant activity in oil-displacement and drop-collapse tests, and its emulsification index reached 79.2% ± 2.51% under the optimized conditions. Fourier-transform infrared spectroscopy identified a peak at 2,984 cm−1 associated with C–H stretching, a peak at 1,736 cm−1 associated with C=O stretching and peaks at 1,233, 1,097 and 1,043 cm−1 associated with C–O–C and C–O stretching. The combination of lipid- and sugar-related bands supported classification as a glycolipid-type biosurfactant, rather than the identification of a particular purified molecule.

The biosurfactant retained substantial emulsifying activity from approximately pH 5 to 9, at temperatures up to 50 °C and at salinities up to 5%, with declining activity beyond those ranges. Residual activity was 94.9% ± 2.73% at 40 °C and 84.3% ± 2.59% at 50 °C. At pH 5 and 9, the respective values were 83.9% ± 2.59% and 81.8% ± 21.6%; at 1% and 5% salinity, they were 83.5% ± 2.04% and 67.4% ± 2.59%. In an oil-removal assay, the biosurfactant recovered 60% ± 2.51% of used engine oil from sterilized soil, compared with 19% ± 3.05% for distilled water and 73% ± 2.08% for Triton X-100.

The principal limitation is that all experiments were conducted under laboratory conditions. The study did not test field performance, environmental persistence or ecological compatibility in contaminated matrices. S. maltophilia is also a recognized opportunistic human pathogen, meaning that any environmental application of the living organism would require rigorous biosafety evaluation. The authors instead point toward possible use of cell-free extracts, purified enzymes or biosurfactant, but note that fuller characterization of the enzymes and biosurfactant would be necessary. The evidence therefore establishes laboratory degradation, reduced seed phytotoxicity and biosurfactant activity, while leaving field effectiveness, product safety and deployment readiness for further study.

Subject of Research: Laboratory evaluation of bacterial phenanthrene degradation and biosurfactant production for petroleum-contamination remediation

Article Title: Phenanthrene degradation and biosurfactant production by Stenotrophomonas maltophilia under static conditions: potential for bioremediation

Article References: Yuvaraja, S., Chakraborty, T., Gomathysankar, J., Kumar, S., & Krishnan, K. (2026). Phenanthrene degradation and biosurfactant production by Stenotrophomonas maltophilia under static conditions: potential for bioremediation. Frontiers in Bioengineering and Biotechnology, 14, Article 1983589. https://doi.org/10.3389/fbioe.2026.1983589

Image Credits: AI Generated

DOI: 10.3389/fbioe.2026.1983589

Keywords: phenanthrene degradation, Stenotrophomonas maltophilia, biosurfactants, bioremediation, petroleum hydrocarbons, static culture conditions, phytotoxicity, glycolipids, oil recovery, laboratory study, Phenanthrene, degradation

The review’s authors, based at ICFAI University Tripura and the National Institute of Technology Agartala in India, ground their analysis in the hard lessons of history. Catastrophes such as the Exxon Valdez, Deepwater Horizon and Hebei Spirit spills have left long-term ecological fingerprints that researchers are still documenting today. Comparative studies cited in the review show that spilled oil can persist in sediments and shorelines for decades, affecting everything from seabird populations to mangrove forests. The 1990-91 Gulf War, for example, left Iranian mangroves degraded for years, while the Prestige disaster off Galicia reshaped both coastal ecosystems and regional politics. Even relatively recent incidents, such as a sanctioned tanker spilling oil in the Baltic Sea near Gotland, demonstrate that the threat has not receded.

Understanding why oil spills are so damaging requires understanding how oil behaves once it hits water. The review details the physicochemical properties of spilled crude, including density, viscosity and the composition of hydrocarbon fractions, and explains how weathering processes transform the slick over time. Evaporation strips the lightest components, leaving behind denser residues that can sink or persist. Emulsification, driven by wave action, can multiply the volume of the pollutant several-fold. Oil also interacts with suspended sediments to form oil-particle aggregates, and recent work shows that marine bacteria play a surprising role in the formation and migration of these aggregates, potentially accelerating the natural removal of oil from the water column. Polycyclic aromatic hydrocarbons, the most toxic fraction, bioaccumulate and travel through marine food webs, reaching coral reef ecosystems and, ultimately, human consumers of seafood.

Detecting a slick quickly and accurately is the first battle, and the review devotes extensive attention to the technology involved. Synthetic aperture radar remains the workhorse of satellite-based oil spill detection because oil dampens the small wind-driven ripples on the sea surface, creating dark patches that stand out against the brighter ocean. Sensors operating in the C-band, such as those on Sentinel-1A, have been used to map spills along the east coast of India, while dual-polarized Radarsat-2 and TerraSAR-X imagery can help distinguish mineral oil slicks from look-alike ocean phenomena. Yet radar has well-known pitfalls: low-wind areas, algal blooms and rain cells can all mimic oil, producing false positives that complicate response decisions.

Optical and hyperspectral remote sensing complement radar by characterizing what the slick actually is. Hyperspectral sensors can identify different types of spilled oil and, in the shortwave infrared domain, estimate slick thickness and emulsion content. Thermal infrared imaging adds another layer of discrimination, and recent research combines hyperspectral data with thermal infrared to improve classification accuracy. For submerged oil, which is far harder to detect than floating slicks, high-spectral polarization detection based on multi-dimensional information represents a cutting-edge frontier. Laser-induced fluorescence, deployed from ships, aircraft and even unmanned underwater vehicles, exploits the fact that petroleum compounds fluoresce when excited by ultraviolet light, allowing responders to map oil that other sensors miss.

The review also highlights how machine learning is transforming spill detection. Algorithms trained on satellite imagery can classify slicks, estimate their thickness and predict their drift, dramatically improving the accuracy and efficiency of response operations. Drone-based fluorosensors and unmanned surface vehicles carrying laser fluorosensors extend monitoring to scales and conditions that crewed aircraft cannot safely reach. In situ sensors are advancing too: dual-modality capacitive-ultrasonic devices can measure floating oil thickness directly, capacitance arrays can detect small leaks from underground tanks, and fiber-optic hydrophones track acoustic signatures in the water column. The authors argue that integrating these active and passive technologies into unified monitoring systems, enhanced by artificial intelligence, should be a research priority.

Once oil is found, the cleanup toolbox offers several options, each with trade-offs. Physical containment with floating booms is the classic first response, but booms perform poorly under strong waves and currents, and structural analysis shows their effectiveness depends heavily on hydrodynamic conditions. Skimmers, from weir-type designs to sponge-covered drums with advanced oleophilic coatings, recover oil mechanically, while sorbents, including hydrophobic chitosan-based materials and natural by-products, soak up slicks at small scales. Chemical dispersants break slicks into droplets that microbes can degrade faster, though their effectiveness in stimulating biodegradation depends on careful formulation and application. In situ burning can remove large volumes of oil quickly, and offshore field experiments have quantified both its burn efficiency and its emissions, but the technique raises air quality concerns and is weather-dependent.

Against these options, the review finds bioremediation to be the most sustainable and economical path. Hydrocarbon-degrading bacteria, including metabolically versatile strains such as Rhodococcus erythropolis isolated from spill-affected lakes, can be deployed as native or engineered consortia, sometimes immobilized on carriers like rice husk biochar to boost their performance in seawater. Biosurfactants produced by microbes such as Pseudomonas cepacia help disperse oil with low ecotoxicity. Fungi contribute through mycoremediation, with species like Trametes, Ganoderma and Trichoderma breaking down stubborn petroleum compounds in soils and sediments, while microalgae such as Nannochloropsis oculata and Chlorella vulgaris can degrade dissolved oil in coastal waters. Plant-based approaches, from duckweed in constructed wetlands to mangroves and salt-marsh grasses, round out the biological toolkit.

Looking forward, the authors identify clear research gaps. They call for integrated monitoring systems that fuse satellite, aerial and in situ data, for environmentally sustainable remediation technologies that avoid trading one form of pollution for another, and for predictive modeling tools that can forecast spill trajectories and ecological consequences before responders arrive on scene. They also connect the agenda to global policy, noting that better oil spill management directly supports United Nations Sustainable Development Goals 6 on clean water and sanitation and 14 on life below water. The bibliometric analysis embedded in the review maps publication trends and emerging themes, giving researchers a roadmap of where the field is heading and where investment is most needed.

The message for policymakers and the public is that oil spill response is entering a data-driven, biology-powered era. Satellites and artificial intelligence can now spot a slick within hours, and carefully managed microbial communities can finish the job that booms and skimmers begin. No single technology is sufficient on its own, but the review makes a compelling case that combining smart detection with sustainable bioremediation offers the best chance of protecting marine and freshwater ecosystems from one of humanity’s most persistent forms of pollution.

Subject of Research: Oil spill detection technologies and sustainable remediation strategies in aquatic environments

Article Title: Managing oil spills in aquatic environments: detection techniques and sustainable remediation strategies

Article References: Dhar, M., Ojha, A., Dey, P., & Das, D. (2026). Managing oil spills in aquatic environments: detection techniques and sustainable remediation strategies. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-026-38257-y

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38257-y

Keywords: oil spills, bioremediation, remote sensing, machine learning, synthetic aperture radar, marine pollution, biosurfactants, mycoremediation, in situ burning, oil spill booms, aquatic pollution, sustainable development goals

The research, published in Discover Green Chemistry by Yog Prakash Yadav, Madhab Gautam, Anju Kumari Das, Sanjay Singh, Chandradip Kumar Yadav, and Ajaya Bhattarai of Tribhuvan University, examines the combined anticorrosive power of saponin and sodium dodecyl sulfate, or SDS, on mild steel immersed in 0.5 molar sulfuric acid. Saponin is a naturally occurring biosurfactant best known as the source of the foamy lather in soap bark, Quillaja saponaria, and soapnut trees. Its molecules carry multiple polar functional groups, including hydroxyl and carbonyl moieties, alongside nonpolar hydrocarbon regions, giving them the amphiphilic character that defines all surfactants. SDS, by contrast, is a synthetic anionic surfactant familiar to anyone who has read the ingredient list of a shampoo bottle. The team reasoned that if the two molecules could cooperate at the steel–acid interface, the resulting protective film might outperform either compound acting alone.

The experimental design was thorough, combining classical gravimetric testing with modern electrochemical and spectroscopic techniques. Mild steel specimens, cut to 3 by 3 centimeter squares containing less than 0.3 percent carbon, were polished with silicon carbide papers of progressively finer grit, from 180 up to 2000, then cleaned in distilled water and sonicated in ethanol for twenty minutes. Pre-weighed samples were immersed in sulfuric acid solutions of varying concentrations, from 0.0125 to 0.5 molar, at temperatures spanning 298.5 to 328 kelvin, for exposure periods ranging from 3 to 96 hours. Some baths contained saponin alone, others contained saponin with SDS, and control baths contained only acid. After immersion, the specimens were reweighed on a precision semi-micro balance, and the weight loss was converted into corrosion rates expressed in millimeters per year.

The gravimetric results told a clear story. Saponin on its own achieved an inhibition efficiency of 64.30 percent at a concentration of 2.92 grams per liter, meaning nearly two-thirds of the corrosion that would have occurred in plain acid was suppressed. When SDS was added to the saponin solution, the efficiency climbed by 13.35 percentage points to 77.66 percent, and the corrosion rate fell to a minimum of 0.37 mils per year in the mixed system. The researchers attributed this improvement to a synergistic effect: the two surfactants interact in solution to form mixed micelles with improved stability, a conclusion supported by conductivity measurements showing that the critical micelle concentration of saponin drops from 0.734 grams per liter to 0.679 grams per liter when SDS is present. A lower critical micelle concentration means the molecules begin assembling into surface-active aggregates at lower doses, which translates into better surface coverage on the metal.

Electrochemical measurements provided even more striking evidence. In potentiodynamic polarization experiments, using mild steel as the working electrode, a saturated calomel electrode as the reference, and graphite as the counter electrode, the team measured corrosion current densities after stabilizing each system at open circuit potential for thirty minutes. Bare steel in sulfuric acid exhibited a corrosion current density of 2.62 times ten to the minus two milliamperes per square centimeter, a signature of severe attack. SDS alone halved the damage, achieving roughly 50 percent inhibition, while saponin alone reduced the current to 8.64 times ten to the minus three milliamperes per square centimeter, corresponding to 67 percent efficiency. But the mixed saponin–SDS system was in a different league entirely: the corrosion current density plummeted to 8.55 times ten to the minus four milliamperes per square centimeter, yielding an inhibition efficiency of 96.70 percent. Crucially, both the anodic reaction, in which iron dissolves into solution, and the cathodic reaction, in which hydrogen gas evolves, were suppressed, identifying the mixture as a mixed-type inhibitor that does not fundamentally alter the corrosion mechanism.

Electrochemical impedance spectroscopy reinforced the picture. Nyquist plots recorded from 100 kilohertz down to 1 hertz showed a very small semicircle for steel in plain acid, indicating low charge transfer resistance and rapid metal dissolution. With inhibitors present, the semicircles grew dramatically, and the largest capacitive loop, the highest charge transfer resistance, and the lowest double-layer capacitance appeared in the saponin–SDS system. Fitting the spectra to a Randles circuit with chi-square values below ten to the minus two confirmed that the mixed formulation delivers inhibition efficiencies of 70 percent or above at the interface. A higher charge transfer resistance means electrons face a greater barrier moving between the metal and the electrolyte, which is exactly what a dense, well-ordered protective film should produce.

Thermodynamic analysis revealed the nature of the protective layer. The experimental data fit the Langmuir adsorption isotherm closely, with correlation coefficients between 0.94 and 0.98 across all temperatures, indicating that the inhibitor molecules arrange themselves as a single monolayer on the steel surface. The standard Gibbs free energy of adsorption remained below minus 20 kilojoules per mole at every temperature tested, a threshold that points to physical adsorption driven by electrostatic attraction and van der Waals forces rather than the formation of new covalent bonds. Notably, both the enthalpy and entropy of adsorption were positive, meaning the process is endothermic and accompanied by increasing disorder, likely as water molecules are displaced from the metal surface. Consistent with this physical mechanism, inhibition efficiency declined as temperature rose, dropping from 93.46 to 80.57 percent for saponin and from 95.55 to 88.33 percent for the saponin–SDS mixture between 298.5 and 328 kelvin, because thermal agitation loosens the grip of adsorbed molecules.

Microscopic and spectroscopic examinations made the protection visible. Optical microscopy revealed extensive pitting and roughening on steel immersed in plain acid, while saponin-treated surfaces were noticeably smoother and the saponin–SDS surfaces were the most intact of all, retaining much of the original polished finish. Field-emission scanning electron microscopy confirmed these observations at higher magnification, showing that the mixed inhibitor preserved the polished surface even in a highly corrosive environment. Energy-dispersive X-ray analysis added elemental proof: carbon and oxygen signals increased on saponin-treated steel, and sulfur appeared when SDS was included, confirming that a carbon-, oxygen-, and sulfur-rich organic film had deposited over the iron. Fourier-transform infrared spectroscopy identified the functional groups involved, including broad hydroxyl stretches near 3400 wavenumbers, carbonyl stretches near 1700, and the characteristic sulfate vibrations of SDS between 1200 and 1300 wavenumbers, with the spectra indicating physical interactions and cooperative adsorption rather than the formation of a new chemical compound.

What makes this work resonate beyond the laboratory is its environmental framing. More than 60 percent of synthetic surfactants used industrially ultimately reach aquatic ecosystems, where petroleum-derived compounds can persist, accumulate in organisms, and harm aquatic life. By anchoring a biodegradable, plant-derived molecule at the heart of the formulation and using the synthetic component only as a synergistic partner, the Nepali team has sketched a template for greener corrosion control: formulations that are effective at low doses, inexpensive, and far less damaging when released. The authors note that efficiency does decline over prolonged immersion as the protective film partially desorbs, and that thermal stability remains a limitation, so engineering challenges remain before industrial deployment. Still, the demonstration that a soap bark extract and a detergent molecule can jointly block more than 96 percent of electrochemical corrosion in sulfuric acid is a vivid reminder that some of the most advanced materials science solutions may be growing quietly in trees, waiting to be tested against humanity’s oldest chemical enemies.

Subject of Research: Synergistic corrosion inhibition of mild steel in sulfuric acid using saponin and sodium dodecyl sulfate

Article Title: Anticorrosive efficacy of saponin and sodium dodecyl sulfate on mild steel specimens immersed in acidic medium

Article References: Yadav, Y. P., Gautam, M., Das, A. K., Singh, S., Yadav, C. K., & Bhattarai, A. (2026). Anticorrosive efficacy of saponin and sodium dodecyl sulfate on mild steel specimens immersed in acidic medium. Discover Green Chemistry, 1(1), Article 10. https://doi.org/10.1007/s44509-026-00008-0

Image Credits: AI Generated

DOI: 10.1007/s44509-026-00008-0

Keywords: corrosion inhibition, mild steel, saponin, sodium dodecyl sulfate, sulfuric acid, surfactants, electrochemical polarization, impedance spectroscopy, Langmuir adsorption isotherm, green chemistry, biosurfactants, physical adsorption

The motivation behind the work stems from a growing environmental reckoning with conventional surfactants. These workhorse molecules, which make up 10 to 20 percent of most cosmetic emulsions, are designed to reduce tension at the boundary between water and oil, allowing otherwise incompatible phases to blend into smooth, shelf-stable products. Yet many synthetic surfactants persist in the environment for years. Perfluorinated compounds in particular are prized by formulators for their robustness but are notoriously resistant to degradation, while linear alkylbenzene sulfonates have been linked to biochemical and pathological harm in aquatic ecosystems. Regulators and consumers alike have been pushing the cosmetics industry to find biodegradable alternatives that do not sacrifice performance.

Biosurfactants, amphiphilic molecules produced by microorganisms that combine a water-loving polar head with an oil-loving hydrophobic tail, have long been touted as such an alternative. Lactic acid bacteria are especially attractive producers because they carry the Generally Recognized as Safe designation, meaning their metabolites face fewer regulatory hurdles in food and personal-care applications. The obstacle has been practical: production yields are often low and fermentation substrates expensive, pushing up costs and limiting commercial adoption. Researchers have therefore been hunting for high-performing producer strains in unconventional places, from cassava-processing effluents to traditional fermented foods.

Pendidam, the spontaneously fermented skimmed cow’s milk consumed around Ngaoundere in Cameroon’s Adamaoua region, had already caught the attention of the research group. Earlier work by Mbawala and colleagues had shown that the drink teems with Lactobacillus strains capable of producing surface-active compounds. In the new study, the team collected six Pendidam samples from vendors at four sites across the city, including the Petit marché, Dang, Wakwa and the Grand marché, and transported them to the laboratory under refrigeration within two hours of purchase.

From those samples the researchers isolated twelve presumptive Lactobacillus strains, all of which proved to be Gram-positive, non-motile, catalase- and oxidase-negative rods with heterofermentative metabolism, growing across a temperature range of 15 to 45 degrees Celsius and tolerating salt concentrations up to 6.5 percent. The authors are careful to note that these phenotypic traits, while consistent with members of the former Lactobacillus group and suggestive of the reclassified genus Lactiplantibacillus, are not sufficiently discriminating for definitive taxonomic assignment following the genus’s recent fragmentation into more than twenty genera; molecular identification by 16S rRNA gene sequencing remains a stated priority for future work.

Screening for biosurfactant production relied on two complementary assays. In the hydrocarbon overlay test, bacterial colonies grown on agar were covered with palm oil; the appearance of clear halos containing microemulsions signaled secretion of surface-active compounds. The oil spreading test provided quantitative confirmation: drops of cell-free culture supernatant were deposited onto a thin oil layer floating on water, and the diameter of the resulting clear zone, which correlates with biosurfactant concentration, was measured. Five isolates, subsequently designated S1 through S5, produced clear zones ranging from 6 to 28 millimeters, comfortably exceeding the 3-millimeter threshold above the negative control that the field considers evidence of genuine biosurfactant production.

The crude biosurfactants were then extracted by ethanol precipitation from scaled-up cultures and put through their paces. Emulsification indices, a measure of the emulsified layer formed when biosurfactant solution is mixed with palm oil, ranged from 67.33 to 72 percent, values slightly below those reported for some purified lactobacilli biosurfactants in the literature but respectable for unpurified crude extracts. More striking were the surface tension measurements. At a concentration of 4 grams per 100 milliliters, solutions of the biosurfactants from isolates S1 and S5 lowered the surface tension of water from 70.90 millinewtons per meter to levels comparable with sodium dodecyl sulfate, the benchmark anionic surfactant used as the positive control.

The decisive test came when the biosurfactants were formulated into water-in-oil beauty milks alongside xanthan gum, sesame oil, glycerol and shea butter, with the commercial sorbitan monostearate SPAN 60 and a marketed body milk serving as positive controls. Laser diffraction analysis using a Malvern Mastersizer 2000 revealed that emulsions stabilized with the bacterial surfactants formed droplets between 4.94 and 7.61 micrometers in diameter, dramatically finer than the 16.34-micrometer droplets of the negative control. The standout was isolate S5, whose biosurfactant yielded the smallest droplets of all, significantly finer even than those produced by the synthetic SPAN 60. According to the authors, this reflects rapid adsorption of the amphiphilic molecules at newly created oil-water interfaces during high-shear homogenization, where they form protective films that generate steric and, depending on molecular composition, electrostatic repulsion between droplets, suppressing coalescence and Ostwald ripening.

Viscosity told a complementary story. Formulations containing the bacterial biosurfactants ranged from 967 to 1715 millipascal-seconds, compared with roughly 1998 millipascal-seconds for both controls, and the differences tracked closely with droplet size. Emulsions with the finest droplets, such as those made with the S5 biosurfactant, maintained relatively high viscosity, consistent with emulsion theory: smaller droplets present a larger total interfacial area, increasing interactions between dispersed and continuous phases and raising resistance to flow. Higher viscosity in turn slows droplet mobility, reducing collision frequency and the risk of creaming or phase separation during storage. The combination of fine droplet size and appropriate rheology, the authors argue, positions the S5 biosurfactant as the most promising candidate of the five tested for cosmetic formulation.

The study’s novelty lies less in the individual measurements than in its integrated approach and its source material. Biosurfactants from lactic acid bacteria have mostly been studied for antimicrobial, antiadhesive and probiotic properties; direct deployment as emulsifiers in cosmetic products has rarely been evaluated, and never before with strains from Pendidam. By connecting microbiological screening with rigorous physicochemical characterization of finished emulsions, the work makes the case that traditional fermented foods are an underexplored reservoir of industrially useful microbes, and one that comes with built-in cultural and economic advantages for the communities that produce them. The path to commercialization still requires purification and structural characterization of the biosurfactants, definitive molecular identification of the producing strains, long-term stability testing and safety evaluation, but the baseline data now exist. For an industry under pressure to replace persistent synthetic surfactants with biodegradable molecules, the answer may have been fermenting quietly in a Cameroonian milk calabash all along.

Subject of Research: Biosurfactants from Lactobacilli isolated from Pendidam fermented milk for stabilizing water-in-oil cosmetic emulsions

Article Title: Improvement of water in oil emulsion physicochemical stability using biosurfactants from indigenous Lactobacilli isolated from Pendidam

Article References: Wandji, V. N., Tsatsop, R. K. T., Mouafo, H. T., & Mbawala, A. (2026). Improvement of water in oil emulsion physicochemical stability using biosurfactants from indigenous Lactobacilli isolated from Pendidam. Discover Industrial Chemistry and Materials, 1(1), Article 20. https://doi.org/10.1007/s44508-026-00021-y

Image Credits: AI Generated

DOI: 10.1007/s44508-026-00021-y

Keywords: biosurfactants, Lactobacilli, Pendidam, emulsifiers, cosmetics, lactic acid bacteria, water-in-oil emulsion, droplet size, viscosity, surface tension, fermented milk, sustainable ingredients

The review, led by Aditya Thapliyal, Aishwary Purohit, Souvik Kumar Paul and Amar Jyoti Das, critically assesses the microbial conversion of sugarcane bagasse into rhamnolipids within circular bioeconomy frameworks. Its central message is that turning bagasse into biosurfactants is not merely an environmental nicety but a technically plausible route to cheaper, more sustainable surfactant production, provided that the right combination of pretreatment, microbial strain engineering, fermentation strategy and downstream processing can be assembled at scale. The authors frame the work explicitly against United Nations Sustainable Development Goal 9 on industry, innovation and infrastructure, and SDG 12 on responsible consumption and production.

The environmental case begins with the waste problem itself. Bagasse that is not burned for energy is frequently dumped or left in the open, where wind disperses it and open burning releases ash, greenhouse gases, particulate matter, nitrogen oxides and carbon monoxide. Inhaled bagasse ash can penetrate deep into the respiratory tract, while landfilling and open dumping generate leachate and harbour pathogens and pests. These hazards have prompted strict regulation: India’s Air Act of 1981 and its 1987 amendment prohibit open burning of agricultural residues, while Brazil has legislated the phased elimination of pre-harvest cane burning under State Law No. 11,241/2002 and the Green Ethanol Agreement, and the United States regulates bagasse combustion under the Clean Air Act. Redirecting bagasse into bioprocesses thus addresses both a pollution problem and a resource opportunity.

Chemically, bagasse is well suited to microbial upgrading. Roughly half of its mass is cellulose, about a quarter hemicellulose and a quarter lignin, with a notably low ash content compared with residues such as rice straw or wheat straw. The cellulose and hemicellulose fractions can be hydrolysed into fermentable sugars, chiefly glucose and xylose, that microorganisms can convert into rhamnolipids. Because bagasse is generated continuously and centrally at sugar mills, it offers a consistent, scalable and inexpensive carbon source, in sharp contrast to the refined glucose, glycerol and vegetable oils that dominate conventional rhamnolipid fermentation and drive up costs.

Rhamnolipids themselves are glycolipid biosurfactants composed of one or two rhamnose sugar units linked to beta-hydroxy fatty acid chains. This amphiphilic architecture lets them cut the surface tension of water from about 72 millinewtons per metre to roughly 25 to 30, and they do so at low critical micelle concentrations, meaning small amounts are effective. They remain stable across wide ranges of pH, temperature and salinity, and they are readily biodegradable and far less toxic than synthetic surfactants. These properties underpin their use in bioremediation, microbial enhanced oil recovery, anti-biofilm pharmaceutical applications, cosmetics, food processing and agriculture as biocontrol agents and formulation stabilizers.

The dominant natural producer, however, is a problem. Pseudomonas aeruginosa synthesizes rhamnolipids through the rhlA, rhlB and rhlC enzymes, regulated by quorum sensing, but it is an opportunistic pathogen classified at biosafety level 2 and is not on the US FDA’s GRAS list, forcing costly containment and purification for food, cosmetic and pharmaceutical uses. The review highlights how metabolic engineering is mitigating this. Replacing the native rhlAB promoter with the stronger constitutive poprL promoter in engineered strain WJPAB raised yields to 57.83 grams per litre, a 91 percent increase over wild type, while systematic gene deletions in strain 8D lifted production from 8.567 to 14.53 grams per litre. Heterologous expression of the rhlAB operon in safe hosts such as Pseudomonas putida KT2440 has produced 40.2 grams per litre in optimized fed-batch fermentation, and non-pathogenic producers including Pseudomonas chlororaphis, Acinetobacter calcoaceticus and Burkholderia thailandensis offer further regulatory advantages, albeit often at lower native yields.

Getting the sugars out of bagasse is the first technical hurdle. Pretreatment options include physical milling, steam explosion, chemical methods using dilute sulphuric acid to hydrolyse hemicellulose or alkali treatments with sodium hydroxide and lime to remove lignin, and biological delignification with fungi such as Trametes versicolor and Phanerochaete chrysosporium. Each approach involves trade-offs: chemical pretreatments can generate fermentation inhibitors, steam explosion is energy intensive, and biological methods are slow. Once sugars are released, fermentation can proceed in batch, fed-batch or continuous modes, with fed-batch generally preferred because it sustains high cell density and supports secondary metabolite production. Carbon catabolite repression, in which glucose suppresses xylose utilization through the Crc/Hfq regulatory system, and careful optimization of the carbon-to-nitrogen ratio, with a ratio of around 22 reported as optimal for one Pseudomonas strain, are key determinants of yield.

Practical demonstrations of the concept are encouraging. Camilios-Neto and colleagues achieved 45 grams per litre of rhamnolipids from Pseudomonas aeruginosa UFPEDA 614 grown on a solid mixture of bagasse and corn bran supplemented with glycerol and soybean oil. El-Housseiny’s gamma-irradiated P. aeruginosa mutant produced 46.85 grams per litre over ten days on bagasse and sunflower seed meal with glycerol, roughly 5.5 times more than submerged fermentation. A co-culture of P. aeruginosa and Saccharomyces cerevisiae on steam-exploded bagasse simultaneously yielded 9.1 grams per litre of rhamnolipids and 8.4 grams per litre of ethanol. Downstream, recovery relies on acid precipitation at low pH, solvent extraction with ethyl acetate, foam fractionation that exploits the molecules’ own surface activity, and membrane ultrafiltration, each balancing cost, purity and environmental burden.

The review insists that neither economic viability nor sustainability claims can rest on substrate choice alone, and it makes a strong case for integrating techno-economic analysis and life cycle assessment. Reported production costs vary almost a hundredfold, from about 7.64 US dollars per kilogram for digestate-based processes to 600 dollars per kilogram in some simulated scenarios, while glucose-based production can reach 56 dollars per kilogram. Fermentation consistently emerges as the dominant environmental hotspot, contributing roughly 76 percent of the global warming potential in one assessment, driven by aeration, mixing and thermal energy demands, while purification steps such as acetone precipitation or solvent extraction account for 35 to 43 percent of the environmental burden in others. Because substrate substitution alone shifts these numbers relatively little, the authors argue that process intensification, energy recovery from residual biomass, solvent recycling and industrial symbiosis with sugar mills offer the greatest sustainability gains.

The market context makes the timing compelling. The global biosurfactant market, in which rhamnolipids are a major component, is projected to grow from about 14.15 kilotons in 2026 to nearly 71 kilotons by 2031, a compound annual growth rate of over 38 percent, driven by consumer demand for eco-friendly ingredients in personal care, agriculture, food and bioremediation. If metabolic engineering, tailored pretreatment, co-product biorefineries and rigorous life cycle assessment continue to converge, the review concludes, sugarcane bagasse could shift from a burning liability to the foundation of economically and environmentally resilient bio-based surfactant production, turning one of agriculture’s largest waste streams into a cornerstone of the circular bioeconomy.

Subject of Research: Microbial production of rhamnolipid biosurfactants from sugarcane bagasse waste in circular bioeconomy frameworks

Article Title: From waste to rhamnolipid biosurfactant production using sugar industry waste in circular bioeconomy frameworks

Article References: Thapliyal, A., Purohit, A., Paul, S. K., & Das, A. J. (2026). From waste to rhamnolipid biosurfactant production using sugar industry waste in circular bioeconomy frameworks. Discover Green Chemistry, 1(1), Article 31. https://doi.org/10.1007/s44509-026-00030-2

Image Credits: AI Generated

DOI: 10.1007/s44509-026-00030-2

Keywords: sugarcane bagasse, rhamnolipids, biosurfactants, circular economy, fermentation, Pseudomonas aeruginosa, lignocellulosic biorefinery, metabolic engineering, life cycle assessment, techno-economic analysis, waste valorization, sustainable development goals