1. INTRODUCTION:

Increasing concerns for the environment and tighter regulatory requirements are accelerating the transition from petroleum-based chemicals to renewable and biodegradable substitutes worldwide and in many industrial sectors. One emerging product category is surfactants, which are amphiphilic molecules that reduce surface/interfacial tension. Conventional surfactants derived from petrochemicals contribute to significant environmental hazards, including a lack of degradability, aquatic toxicity, and persistent organic pollutants. As a result, it is critical to develop bio-based surfactants from renewable feedstocks, which coincide with the principles of green chemistry, and support a sustainable approach to development^1-2. Bio-based surfactants have many advantages, including greater biodegradability, reduced toxicity, and environmental impact. These alternatives can be derived from renewable sources such as plant oils, sugars, and microbial fermentation. Bio-based surfactants not only address environmental and sustainability concerns, but also provide opportunities for innovation in product formulation and performance for personal care, household cleaning, and industrial products^3-6. Due to their abundance, structural diversity, and inherent biodegradability, vegetable oils and their derivatives have grown to become the most promising renewable feedstocks for the production of bio-based surfactants. These oils mainly consist of triglycerides that are high in unsaturated fatty acids and are ideal precursors for chemical modification to develop a variety of surfactant molecules. The methyl and ethyl esters of vegetable oils produced by transesterification reactions are valuable intermediates for chemical modification. The long hydrophobic alkyl chains and functional groups based on esters of fatty acids can yield a variety of modifications (e.g., epoxidation, ethoxylation, amidation) with varying surface-active properties. An example of the variety of modifications these compounds can undergo is epoxidation reaction, which places a reactive oxirane group across an unsaturated bond, which can then undergo a subsequent ring-opening reaction to yield a polyhydroxylated surfactant with enhanced desired hydrophilic properties. An example of another example of variation is ethoxylation, whereby ethylene oxide is strategically added to modify a hydrophilic–lipophilic balance (HLB), which optimized solubility and detergency. Utilization of fatty acid esters with alkanolamines or amino alcohols to produce amide surfactants take advantage of emulsification properties that combine mildness and biodegradability with stability. The fact that these compounds are renewable provides an additional environmental benefit and decreases the carbon implications of surfactant production and utilization when compared to petroleum derivatives. In addition, the structural compatibility of derivatives of vegetable oils to biological degradation pathways allows for their degradation in the environment^7-12.

Environmental sustainability metrics biodegradability, aquatic toxicity, and life cycle assessment are now key aspects of evaluating and designing new surfactants. Research has shown that bio-based surfactants performed better in biodegradation with degradation rates often exceeding 90% in accordance with OECD protocols. The favourable biodegradability in bio-based surfactants can be primarily attributed to labile functional groups (ester, amide, glycosidic bonds) that can be hydrolysed or enzymatically cleaved in the aquatic environment^12-16. In addition, using low-cost, non-food, and waste oils, such as waste cooking oils, jatropha, neem, and castor oil, can also be aligned with the principles of green chemistry and circular economy. These feedstocks can both minimize waste production and prevent the competition for food oils. Converting renewable raw materials into effective, biodegradable surfactants can foster a sustainable value chain to establish an environmentally responsible industry with a balance between performance and sustainability. Therefore, increasing attention is being made for vegetable oil space surfactants for diverse applications, including detergents, personal care, textiles, and leather to further transition sustainable chemical manufacturing practices^14-16.

This literature review provides a thorough assessment of major classes of bio-based non-ionic & anionic surfactants, focusing on their synthesis mechanisms, catalytic approaches, and structure-property relationships: fatty ester derivatives, fatty amide surfactants, methyl ester sulfonate, and citric acid esters. It considers recent developments in reaction pathways, catalyst designs, and green chemistry strategies to shed light on the mechanistic basis for efficient and sustainable surfactant production. Mechanisms - both catalytic and reaction based are necessary to understand to further develop the industrial-scale application of bio-surfactants, and subsequently the next-generation bio-surfactants that will meet performance criteria and have environmental viability. The intersection of renewable feedstocks, active catalysts, and mechanistic understanding marks a foundational movement towards truly sustainable surfactant chemistry, while also extensible to the larger aspirations of green chemistry and the circular bioeconomy.

2. NON-IONIC SURFACTANTS DERIVED FROM FATTY ACID AND VEGETABLE OIL:

The use of renewable fatty sources for the synthesis of non-ionic surfactants has been given significant interest as a replacement for traditional petroleum-based surfactants because of their mildness, biodegradability, and adjustable physicochemical properties. The methyl and ethyl esters of vegetable oils are valuable intermediates for the manufacturing of green surfactants. Among different modification strategies, ethoxylation and epoxidation with subsequent ring-opening reaction with polyethylene glycols (PEGs) have come up as green approaches for the production of non-ionic surfactants with variable hydrophilic–lipophilic balance (HLB) and surface activity. These routes not only provide versatility in the control of surfactant performance but also embrace the principles of green chemistry in employing renewable resources and avoiding toxic reagents The synthesis of non-ionic surfactants from fatty acid and vegetable oil derivatives offers a sustainable alternative to conventional petroleum-based products. These bio-based surfactants can be tailored to meet specific application requirements by adjusting their molecular structure and composition. The ability to fine-tune properties such as HLB and surface activity makes these surfactants particularly attractive for use in various industries, including personal care, household cleaning, and industrial applications.¹⁷ Recent progress shows that epoxidized oleate esters can be successfully functionalized through solventless, heterogeneously catalysed ring opening with PEGs of different chain lengths. A three-step synthesis pathway for transesterification of methyl oleate to alkyl oleates, epoxidation of olefinic double bonds, and ring opening with PEGs at mild conditions has been reported by Ogunjobi et al. with yields greater than 80% and minimal side reaction¹⁷. The surfactants formed had critical micelle concentrations (CMC) less than 0.1 mg/mL, showing high surface activity. The research highlighted that the manipulation of alkyl chain length and PEG molecular weight tunes surfactant polarity and micellization behaviour, which are key for use in detergents, emulsifiers, and wetting agents. Significantly, the heterogeneous catalytic system substituted conventional corrosive catalysts like boron trifluoride, erbium triflate, or tin tetrachloride and hence improved process sustainability. Parallel developments have also been noted in the creation of Polyoxyethylene fatty acid ester surfactants, which include biodegradable linkages to enhance environmental performance. European Patent EP0844016A2 discloses PEG–fatty acid esters with methylene diester units (-CO–O–C(R1) (R2)–O–CO-), which exhibit higher biodegradability than traditional PEG esters.¹⁸ These surfactants are structurally arranged to enable controlled hydrolytic cleavage, enabling enhanced rapid biodegradation in aquatic settings. The equilibrium between fatty acyl chain length and PEG polymerization level allows modulation of HLB values, facilitating use as antistatic agents, solubilizers, emulsifiers, and conditioners in cosmetic and pharmaceutical products¹⁸. Use of biodegradable linkages is an important advance toward implementing environmentally benign non-ionic surfactant systems The incorporation of methylene diester units in PEG-fatty acid esters represents a significant advancement in surfactant design, addressing both performance and environmental concerns. These novel structures offer improved biodegradability while maintaining the versatility and functionality of traditional PEG esters. The ability to fine-tune the hydrophilic-lipophilic balance through careful selection of fatty acyl chain length and PEG polymerization degree provides formulators with a powerful tool for developing tailored surfactant solutions across various applications. Fatty acid ester ethoxylation is another pillar of surfactant synthesis. Lukosek et al. prepared and characterized ethoxylated methyl and ethyl esters of unsaturated fatty acids via calcium-based and aluminium–magnesium oxide catalysts under reaction conditions that were optimized¹⁹. Gas chromatography and mass spectrometry established that catalyst composition was responsible for significant effects on product distribution and by-product suppression. The resultant ethoxylated esters showed attractive physicochemical properties such as low foaming, very good emulsification, and high biodegradability. In addition, OECD-guideline-compliant biodegradation studies supported the environmentally friendly profile of these surfactants and asserted their compatibility in detergents, textile lubricants, and personal care products. The results also underscore that the increasing market for non-ionic surfactants is prompted by regulatory forces and consumer calls for safer, biodegradable products. In addition to ethoxylation, transesterification of fatty esters is still a crucial method for obtaining intermediates for the synthesis of surfactants. Olutoye and Hameed showed how to effectively transesterify used cooking oil into fatty acid methyl esters (FAMEs) by employing a reusable Mg–Zn mixed oxide catalyst²⁰. Under mild conditions, the process produced an ester yield of 80% and demonstrated the possibility of turning waste oils into useful raw materials for the synthesis of surfactants. By turning waste into useful bio-based chemicals, this is consistent with the ideas of the circular economy. In a similar vein, Nguyen produced polyethylene glycol ester surfactants that were tailored for water-in-oil emulsions, highlighting their function in improving interfacial tension control and stabilizing multiphase systems ²¹. Rapeseed methyl ester ethoxylates (RAMEE) are a promising class of bio-based non-ionic surfactants that exhibit superior surface performance and biodegradability. According to Renkin et al.'s assessment of RAMEE's eco-profile, they are less ecotoxic and have detergency comparable to alcohol ethoxylates²². RAMEE surfactants have favourable rheological characteristics, high solubility, and good cleaning efficiency. They also blend in perfectly with liquid detergents. Their synthesis emphasizes regional sustainability by utilizing rapeseed oil, a plentiful feedstock in Europe. The direct ethoxylation of inedible Jatropha and leftover vegetable oils was also shown by El-Shattory et al. and Nashy et al. to produce non-ionic fat liquors appropriate for leather finishing^23-24. The functional potential of these ethoxylated products was confirmed by their superior oil-in-water emulsification stability and enhanced leather softness, tensile strength, and elongation at break. These ethoxylated products exhibited excellent oil-in-water emulsification stability and improved leather softness, tensile strength, and elongation at break, confirming the functional potential of bio-derived non-ionic surfactants in industrial applications. The development of fatty ester-based non-ionic surfactants illustrates a synthesis of sustainable chemistry, catalytic processes, and enhanced material functionality. The use of renewable feedstocks like vegetable oils, the application of heterogeneous catalytic systems, and the creation of biodegradable linkages together tackle the environmental challenges posed by conventional surfactants. Recent developments in synthesis methods like epoxidation, ethoxylation, and transesterification allow for meticulous control over molecular structure and HLB, thereby customizing surfactant behaviour for targeted applications. The advancements being made are leading us toward a new era of sustainable surfactants that fulfil both performance and environmental standards.

3. SYNTHESIS MECHANISMS OF FATTY AMIDE-BASED SURFACTANTS:

Eco-friendly Synthesis of Non-ionic Surfactants from Renewable Feedstocks: A Brief Review Recent advancements in surfactant chemistry highlight the shift from petrochemical sources to renewable feedstocks for the production of sustainable surfactants. The conversion of vegetable oil waste and by-products into non-ionic surfactants presents a promising pathway for manufacturing aligned with circular economy principles. Abdiyev et al. synthesized fatty carboxylic acid monoethanolamide (FCA-MEA) and diethanolamide (FCA-DEA) surfactants from sunflower oil production waste via alkaline hydrolysis followed by amidation, achieving yields exceeding 90%. The diethanolamide derivative demonstrated enhanced surface activity and emulsion stability, highlighting its potential application as a foaming and emulsifying agent in detergents and cosmetics²⁵. In parallel, WO2010042462A1 describes a method for synthesizing non-ionic surfactants via the ethoxylation of fatty acid esters, utilizing a controlled approach for the addition of ethylene oxide to improve product consistency and minimize by-products^25,26. The patent emphasizes techniques for process intensification that reduce energy input while attaining high conversion efficiency, presenting an industrially scalable method that aligns with the principles of green chemistry. In a similar vein, US20240218287A1 presents structured non-ionic surfactant compositions designed for high-performance cleaning. These compositions incorporate bio-based alcohols with ethoxylated or propoxylated chains to enhance the hydrophilic–lipophilic balance and improve foam control²⁷. The combination of renewable feedstocks, advancements in catalysts, and refined reaction pathways (such as ethoxylation, amidation, and esterification) significantly improves surfactant efficacy while reducing environmental consequences. The movement towards multifunctional and biodegradable surfactants demonstrates the industry's dedication to sustainability. Recent investigations demonstrate that renewable non-ionic surfactants not only meet but frequently exceed the efficiency and stability of traditional petroleum-based counterparts. Future advancements are expected to focus on enzymatic catalysis and continuous-flow processes to enhance the efficiency of green synthesis. Fatty amide–based surfactants, especially fatty alkanolamides like monoethanolamide (MEA) and diethanolamide (DEA) derivatives, constitute a significant category of non-ionic surfactants sourced from renewable oils. These substances find extensive application in detergents, cosmetics, lubricants, and petroleum formulations due to their biodegradability, mildness, and emulsifying properties. The formation of these compounds occurs via the amidation process involving fatty acids, fatty acid methyl esters, or triglycerides in conjunction with alkanolamines. The effectiveness of amidation is influenced by several factors, including the catalyst, temperature, molar ratio, and energy input method, all of which play a crucial role in determining the conversion rate and purity of the resulting surfactant. Two main pathways are utilized in the amide surfactant synthesis enzymatic catalysis and chemical (heterogeneous or homogeneous) catalysis, with recent developments also involving non-catalytic microwave and green solvent-free processes. Masyithah maximized the lipase-catalysed oleic acid and diethanolamine amidation by using Response Surface Methodology (RSM). The investigation detected an optimum at 60–65°C with a 1:3 molar ratio of DEA/OA, 5–9wt% enzyme loading, and obtained 78% conversion. The immobilized Candida antarctica lipase showed regioselectivity and stability, validating the feasibility of enzymatic amidation at low temperatures²⁸. In the same way, Suhendra et al. immobilized Calophyllum inophyllum kernel oil by lipase Thermomyces lanuginosus (Lipozyme TL IM) to yield fatty diethanolamide with a 44% yield within 2h at 40°C. Biocatalytic pathways offer high selectivity and less side products but are bounded by enzyme expense and greater reaction time²⁹. Chemical catalytic systems are more practical for industrial purposes by virtue of greater throughput. Kumar et al. illustrated one-pot solvent-free amidation of triglycerides with Li-doped CaO nanoparticles, resulting in 98 % conversion of pongamia and jatropha oils in 1h at 90°C. The solid catalyst was recyclable up to six cycles without notable loss in activity³⁰. Utami et al. utilized K₂CO₃-modified zeolite for amidation of methyl esters obtained from waste cooking oil, giving 92% diethanolamide³¹. The heterogeneous catalyst offered increased surface basicity and avoided product phase contamination. Heterogeneous catalysts were the focus in both studies as environmentally friendly substitutes for homogeneous alkalis (KOH, NaOH, CH₃ONa), which tend to produce wastewater and make purification difficult. Microwave irradiation has been investigated to enhance the amidation process. Ginting et al.obtained a 98.89% conversion of palm fatty acid distillate (PFAD) and MEA under microwave radiation at 100% power in 18.5min³². The non-catalytic process is based on uniform heating and dipole polarization of reactants, greatly speeding up the nucleophilic substitution. This new method avoids catalyst separation and provides an energy-efficient way of synthesizing bio-surfactants. Variability in feedstock also affects product properties. Sari et al. studied the alkaline conversion of coconut and palm oil to alkanolamides with KOH catalyst³³. Coconut oil was observed to produce products of higher purity and lower viscosity, whereas palm oil, being more unsaturated, was susceptible to oxidation. Pawignya et al. have described a two-step esterification followed by amidation of methyl esters of palm oil with DEA employing NaOH with 68.95 % conversion and CMC value of 5 g/mL. These examples illustrate how fatty acid profile controls hydrophilic–lipophilic balance (HLB) and emulsifying properties³⁴. Chemical amidation mechanism follows the mechanism of nucleophilic acyl substitution. First, the diethanolamine nitrogen molecule attacks the electrophilic carbonyl carbon of a fatty acid or ester to yield a tetrahedral intermediate. The intermediate collapses with loss of leaving group water in direct amidation or methanol in aminolysis of esters to give the fatty alkanolamide. Ongoing removal of water or alcohol pushes the equilibrium towards amide formation. Hartyányi et al. and Yanovsky et al. (2018) stressed the fact that amidation of fatty acids involves high temperatures (150–180°C) and effective dehydration to inhibit esterification side reactions³⁵. In heterogeneous catalysis, basic sites on CaO or zeolite activate the carbonyl group, promoting nucleophilicity of amines and transition state stabilization, consequently lowering activation energy. In enzymatic amidation, the process involves an acyl-enzyme pathway. Lipase first acts on the fatty acid or ester to produce an acyl-enzyme intermediate through its active-site serine. This intermediate is then attacked by diethanolamine with expulsion of the amide product and restoration of free enzyme^36-37. The reaction is carried out under mild conditions (40–70 °C) with prevention of oxidation of unsaturated fatty acids. The hydrophobic environment of the immobilized lipase promotes long-chain substrate binding, thus its high selectivity in oleic and lauric acids. The microwave-activated mechanism, as reported by Ginting et al., is based on the quick energy uptake by polar molecules like MEA, resulting in localized superheating and molecular agitation^37-38. The influence raises the frequency of amine and carbonyl group collisions and reduces the reaction time significantly. The process is similar in basic nucleophilic substitution but enjoys faster kinetics with no added catalysts. Solvent and physical parameters also become very important. Masyithah et al. reported 4:1 solvent ratio (tert-amyl alcohol/FAME) and stirring rate of 300rpm to be the optimal for conversion of fatty acid methyl esters into coco-monoethanolamide with ZrCl₄ as catalyst. Ideal mixing enhances mass transfer between non-polar and polar phases, while stabilization of intermediates and avoiding localized overheating are provided by solvents. The reaction pathway and yield are consequently greatly affected by mechanical, and solvent conditions.

4. SYNTHESIS MECHANISMS OF CITRIC ACID ESTER SURFACTANTS:

Citric acid-derived surfactants are a promising group of biodegradables, mild, and multifunctional amphiphiles with considerable interest as renewable replacements for petroleum-derived surfactants. Their synthesis generally takes advantage of the multifunctional nature of citric acid, having three carboxyl and one hydroxyl group, allowing selective esterification with numerous hydrophobic alcohols or sugar derivatives. Initial synthetic methods depended on esterification of citric acid directly with fatty alcohols under elevated temperature (120–140°C) and low pressure, as mentioned in initial patents and commercial compositions. The conditions usually yielded intricate mixtures of mono-, di-, and tri-esters with the yield being merely 60–70%, and the products were darkened and insoluble because of over-esterification^39-40. A significant innovation was presented by Weil and co-workers at Lever Brothers, who reported an indirect, anhydride-mediated pathway to salts of citric acid monoesters with long-chain alcohols (C₁₀–C₁₈). Here, the initial conversion of citric acid to citric acid anhydride is achieved using acetic anhydride, and the anhydride is subsequently esterified with a fatty or polyglucoside alcohol to give a monoester with very little diester or tri-ester formation⁴¹. The most important benefit of this path is its selectivity: the cyclic anhydride intermediate restricts over-esterification through the presence of a single reactive carbonyl that is accessible to nucleophilic attack. Neutralization with sodium or potassium hydroxide then generates water-soluble monoester salts, often in yields greater than 90%. The surfactants have good foamability, good stability in hard water, and skin mildness because of the presence of more than one carboxylate group as inherent complexing agents ^42-43. The mechanism of the reaction is a nucleophilic acyl substitution route via the electrophilic carbonyl of citric acid anhydride. Intramolecular dehydration of two carboxyl groups of citric acid first forms the cyclic anhydride intermediate. When treated with an alcohol or polyglucoside (ROH), the carbonyl carbon of the hydroxyl oxygen attacks to give a tetrahedral intermediate that collapses to produce the monoester and regenerate a free carboxyl group. Neutralization of the excess unreacted carboxyls produces the disodium salt of the monoester, giving an amphiphilic molecule with hydrophobic alkyl tails and hydrophilic carboxylate headgroups. This regulated esterification prevents uncontrolled poly-substitution that is characteristic of direct heat, retaining monoester purity and consistent performance. Subsequent progress extended this chemistry to sugar- and ethoxylate-type systems to reach hybrid surfactants with tunable hydrophilic–lipophilic balance (HLB) and good water solubility. Research by Zhou et al. and Zhu et al. illustrated the effective synthesis of alkyl polyglucoside citrates (APG-EC) and alkyl mono-glucoside citric monoesters (AG-EC) through this indirect anhydride route from glucose-derived alcohols and natural fatty alcohols. These anionic green surfactants-maintained mildness and biodegradability of alkyl polyglucoside but addressed their poor solubility. Structural confirmation by FTIR indicated disappearance of bands due to anhydrides (~1800 cm⁻¹) and appearance of strong ester carbonyl peaks at ~1735 cm⁻¹, whereas LC–MS spectra established monoester molecular ions, supporting the suggested mechanism^39-42. Surface tension measurements showed that AG-EC and DAPGC surfactants lowered surface tension to approximately 28 mN m⁻¹ and exhibited low critical micelle concentrations (CMC) and, thus, were efficient surface adsorbents. Gibbs adsorption isotherm calculations predicted high surface excess and tight interfacial packing. The carboxylate groups of the citric moiety in these molecules interact by hydrogen bonding and electrostatic repulsion, and the hydrophobic tails aggregate to form stable micelles. The presence of ethoxylated or glycosidic linkages improved hydrophilicity and foaming stability with sustained performance even in hard water. European Patent EP 0199131 A2 also indicated citric acid esters of polyoxyethylated alcohols with the chain length C₈–C₂₀ and 4–8 ethoxy units, showing adjustable solubility and good compatibility with other surfactants while maintaining > 90% biodegradability⁴³. The mechanism is similar: nucleophilic attack of the ethoxylated alcohol hydroxyl on citric acid anhydride results in mono- or diester formation, the distribution of product being determined by reactant molar ratio. These molecules, along with the multifunctional citrate esters disclosed in WO 1999059406 A1, represent the union of mechanistic accuracy and molecular design, generating surfactants that balance hydrophobic–hydrophilic interactions through controlled ester architecture. Together, these researches prove that anhydride-catalysed esterification of citric acid allows for rational preparation of well-defined monoesters with better interfacial activity, stability, and environmental compatibility, making citric acid derivatives a pillar in the area of bio-based surfactants.^43-44.

5. METHYL ESTER SULFONATE:

Methyl ester sulfonate (MES) is a newly developed green anionic surfactant that is made from renewable oils including palm, sesame, and used cooking oil. As there are increasing concerns about the ecological impact of surfactants from petrochemicals, MES provides a biodegradable, inexpensive and high-performance alternative. It is synthesized in two steps, the transesterification of oils to conduct methyl esters then the sulfonation. The resulting surfactant formulation has excellent detergency and calcium tolerance even in hard water⁴⁴. Sahila et al. described the synthesis of MES from palm oil using microwave-assisted transesterification and sulfonation with sodium bisulfite as the sulfonating agent and CaO as the catalyst. The reaction produced a yield of up to 98.67% and obtained a surface tension of 32.23 dyne/cm. The microwave energy resulted in significant time savings and increased efficiency over normal heating⁴⁴. Expectingly, Qadariyah et al. also optimized the process and obtained a product with a surface tension of 27.34 dyne/cm and a high level of biodegradability, while demonstrating that this approach is both green and energy efficient ⁴⁵. Recent research has centered on waste valorization to enhance sustainability. For instance, Yusmin and Jumal (2025) synthesized MES from used cooking oil (UCO), changing that waste to a high value ingredient in detergent. They used KOH as a catalyst and ZnO nanoparticles to improve cleaning efficiency, while incorporating carboxymethylcellulose (CMC) to stabilize the product. Nanoparticles improved detergency even further while also introducing antibacterial and photocatalytic synergies that opened avenues for new nanofluid detergent^46-47. In addition to palm and waste oils, sesame oil demonstrates other novel renewable feedstocks. Soy et al. synthesized sesame fatty methyl ester sulfonate (SEFAMESO) while confirming successful formation of the interfaced surfactant complex using FTIR, NMR, and HPLC-MS. The SEFAMESO surfactant complex had lower critical micelle concentration (CMC) than sodium dodecyl sulfate (SDS), indicating enhanced surface activity. The SEFAMESO surfactant was exothermic and showed signs of stable spontaneous micellization thermodynamics confirming its application use in detergents and cosmetics^48-49. MES has shown better performance over traditional surfactants in detergent formula. Murad et al. studied palm derived C16/18 MES in liquid detergents and found good detergency, stability, and biodegradation above 60% in 3-8 days, much sooner compared to LAS which was up to 24 days⁵⁰. Lim et al. studied α-sulfo methyl ester sulfonate (α-MES) vs LAS and found MES to have excellent cleaning performance in hard water conditions allowing for a reduction in builder dosage of up to 33% without losing performance with MES compared to LAS. The higher tolerance for calcium ions and increased interfacial activity make MES advantageous^51-52. Overall, MES is a major innovation for greener surfactant technology. Its renewable oil-based synthesis through efficient catalytic and microwave-assisted synthesis offers a pathway for high-performance performance detergents. Studies have continued to show that MES offers great cleaning efficiency, high biodegradability, and tolerance to hardness to be a good and environmentally friendly alternative to petrochemical based surfactants in both home and industrial posing multiple applications.

6. SUMMARY:

The production of bio-based surfactants from renewable sources is an important development in sustainable chemistry. Mechanistic studies show that the three transesterification routes, together with ethoxylation, amidation, and sulfonation, lead to the design of effective surfactants with tunable hydrophilic lipophilic balances (HLB) and levels of biodegradability. The use of waste or non-food oil substrates makes the production more environmentally and economically sustainable by reducing dependency on petrochemical feedstocks. The use of heterogeneous catalysis, enzymatic measures, and microwave processes improve selectivity, energy efficiency, and reduce waste. In terms of surfactants, fatty amide and citric acid-based surfactants are mild and biodegradable, while methyl ester sulfonates have the best detergency and hardness tolerance. Overall, moving toward this type of surfactant manufacturing is a major step toward green surfactants that support a circular economy and low-carbon industry. Ongoing studies on catalyst design, process intensification, and life-cycle assessment will be important to continue developing bio-based surfactants beyond laboratory proof of concept and into industrial scale use.

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Received on 01.11.2025 Revised on 23.12.2025

Accepted on 02.02.2026 Published on 25.04.2026

Available online from April 28, 2026

Research J. Science and Tech. 2026; 18(2):165-172.

DOI: 10.52711/2349-2988.2026.00023

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