Green Solvent-Based Antimicrobial Microemulsions: Formulation and Evaluation of Methyl Ester-Camphor Oil Systems for Surface Cleaning

Harshal Patil, Jyotsna Waghmare

Department of Oils, Oleochemicals and Surfactant Technology Institute of Chemical Technology

(ICT), Nathalal Parikh Marg, Matunga (E), Mumbai-400019, Maharashtra. India.

*Corresponding Author E-mail:

ABSTRACT:

The design of eco-friendly antimicrobial preparations is one of the crucial issues to be considered in terms of resolving the health- and ecological-related problems related to the use of traditional synthetic disinfectants. The study presents the development and an overall analysis of new green solvent based antimicrobial microemulsions using neem oil methyl ester, camphor oil, and ethoxylated vegetable oils as totally bio-based materials. Surfactants of different hydrophilic-lipophilic balance (HLB) (9.7, 11.7 and 12.5) were added to two oil blends (80:20 and 60:40 camphor oil to neem oil methyl ester) to create both the oil-in-water (O/W) and water-in-oil (W/O) microemulsion systems. Pseudo-ternary phase diagrams were plotted to establish stable microemulsion areas and twelve formulations were properly characterized based on physicochemical characteristics such as pH, density, conductivity, particle size, and stability. Dynamic light scattering examination showed that the size of the particles varies between 81.90 nm and 189.2 nm, and all of the preparations showed very good thermodynamic stability in 30 days. The testing of antimicrobial efficacy under the requirements of EN 1040:2005 standards showed a strong activity against Staphylococcus aureus and Escherichia coli, where log reductions were 2.90 to >4.35 and the percentage reductions were 99.87% to >99.99% on a 5-minute contact. It is worth mentioning that the Blend-1 JO-5 formulation (80:20 oil blend with HLB 11.7) showed the best antimicrobial activity with more than 4.35 log reduction to S. aureus. The findings support the argument that methyl ester solvents and fully bio-based microemulsion systems in soil cleaning applications can be used to offer an alternative to the synthetic disinfectants, as these systems are stable and can offer effective and efficient systems to counteract microorganisms, at the same time being environmentally sound.

KEYWORDS: Green Solvents, Antimicrobial Microemulsions, Neem Oil methyl Ester, Camphor Oil, Cleaning Agents.

1. INTRODUCTION:

The global trend of environmental sustainability and growing concern for human health and ecological safety have catalysed intensive research into the development of green alternatives to traditional synthetic disinfectants and cleaning agents. Most traditional surface disinfectants, though highly effective against microbes, are dominated by synthetic chemicals, petroleum-derived solvents, and VOCs that pose serious risks to human health, contribute to indoor air pollution, and form persistent organic pollutants in the environment.^1-2 Concerns about skin sensitization, respiratory irritation, aquatic toxicity, and the emergence of antimicrobial resistance have also been raised with the widespread use of quaternary ammonium compounds, chlorine-based disinfectants, and alcohol-based sanitizers. There is, therefore, a pressing need for the development of nontoxic, biodegradable, and efficient antimicrobial formulations that can deliver high performance with a minimum of detrimental environmental and health impacts.^3-4

Natural oils of botanical origin and their derivatives have been widely recognized for their tremendous potential for antimicrobial, antifungal, and antiviral activities; thus, they have had a significant role in various systems of traditional medicine for thousands of years. The interest in botanical antimicrobials is steered by their complex phytochemical compositions, multi-target mechanisms of action that reduce the likelihood of resistance development, and their innate biodegradability.^5-6 Among the large number of medicinal plants studied, neem, Azadirachta indica, has emerged as one of the most promising sources of bioactive phytoconstituents with broad-spectrum antimicrobial action. Neem oil is rich in limonoids, triterpenoids, and fatty acids, with major active principles such as azadirachtin, nimbin, nimbidin, and gedunin.^7-8 These compounds have been found to be active against a wide array of Gram-positive and Gram-negative bacteria, fungi, and some viruses due to several modes of action, including disruption of cellular membranes, interference with protein synthesis, and inhibition of enzymatic activity.^9-13

Complementing the antimicrobial profile of neem, camphor oil from Cinnamomum camphora has shown strong antibacterial, antifungal, and insecticidal properties, arising from its rich monoterpene composition. Camphor, 1,8-cineole, α-pinene, camphene, and limonene are major bioactive compounds in camphor oil; their combined contribution to the antimicrobial efficacy of camphor oil is based on membrane disruption, induction of oxidative stress, and interference with microbial metabolic pathways. In this context, neem oil mixed with camphor oil might represent a promising natural antimicrobial system, with possible enhanced efficacy because of the complementary modes of action for both components and acceptable safety. However, a number of challenges regarding their inherently hydrophobic nature, high volatility with rapid evaporation and loss of activity, poor aqueous solubility, chemical instability under ambient conditions, and difficult uniform distribution on surfaces^14-19 have so far greatly restricted their practical application in commercial formulations. Thus, proper formulation of delivery systems by using environmentally benign solvents and bio-based surfactants is critical for the translation of this antimicrobial potential into effective, stable, and commercially viable products. This meets the broader principles of green chemistry, namely renewable feedstocks, reduction of hazardous substances, and design of safer chemicals and procedures.^20-25 The use of methyl esters in the organic phase of microemulsion formulations meets several goals for sustainability: reduces dependence on fossil fuel-derived solvents, opens additional value streams for biodiesel and vegetable oil processing, provides minimal environmental impact due to biodegradability, and maintains performance characteristics required for effective formulation stability and delivery against microbes. Furthermore, the structural diversity possible with methyl esters from a wide array of plant sources such as jatropha, grapeseed, soybean, palm, or other oil crops allows for optimization of solvent properties in concert with those required by a formulation and regional agricultural availability.^26-28 Despite the years of research into natural antimicrobials, green solvents, and bio-based surfactants, surprisingly few works have focused on the formulation of a complete, all biobased microemulsion system that brings these components together in synergy for practical applications in surface disinfection and cleaning. Most publications involve either proof-of-concept demonstrations with single natural antimicrobials or investigations of green solvents in isolation without considering complex formulation challenges associated with the creation of stable, effective, commercially viable products. Moreover, only a few studies so far have explored the particular combination of methyl ester solvents with neem-camphor oil antimicrobial blends stabilized by ethoxylated vegetable oil surfactants, despite such a system offering a theoretically advantageous combination of complete bio-based composition, potential synergistic effects, and circular economy principles.^28-32

This work aims to fill this gap by formulating and comprehensively evaluating novel, green solvent-based antimicrobial microemulsions composed of methyl esters as the organic phase, a neem-camphor oil blend as natural antimicrobial agents, and ethoxylated vegetable oil as a bio-based surfactant system. The study will involve formulation optimization through systematic investigation of component ratios and processing parameters, detailed physicochemical characterization including droplet size analysis, stability assessment, rheological profiling, and interfacial property evaluation, comprehensive antimicrobial efficacy testing against relevant pathogenic microorganisms, and practical surface cleaning performance evaluation under conditions representative of real-world applications. This paper is intended to contribute to the advancement of the principles of green chemistry in the development of antimicrobial formulations, provide an overview of the behavior of fully bio-based microemulsion systems, and present a practically applicable and environmentally friendly method of surface disinfection and cleaning that considers modern issues of sustainability, human health, and ecological safety.

2. MATERIALS AND METHODS:

2.1 Materials:

The oil used in the study was camphor oil, which was acquired at a local supplier and neem oil methyl ester, which was acquired at Rossari Biotech ltd, Mumbai. The emulsifying agents were castor oil ethoxylated with 35 moles of ethylene oxide (HLB 12.5), Jatropha oil ethoxylated with 15 moles (HLB 9.7) and 20 moles (HLB 11.7) of ethylene oxide both purchased at the Rossari Biotech Ltd. Reagents and chemicals used were of analytical grade and the suppliers were reputable and not purified further. To reduce ionic interactions, which would affect the outcomes of the experiment, deionized water that is less conductive than 1 uS/cm was used during the experimental process to enhance reproducibility.

2.2 Methods:

2.2.1 Characterization of Camphor oil & Neem oil methyl ester.

The characterization of camphor oil and Neem oil methyl ester was done to ascertain their physicochemical properties in as far as formulation development is concerned. The analyses were density, acid value, saponification value, and iodine value, Optical rotation, Refractive index of standard AOAC procedures. The data were measured at ambient temperature both in controlled lies within the laboratory to guarantee consistency and accuracy.

2.2.2 Preparation of Oil Blends:

Two blends of oil were made in various weight proportion of neem oil methyl ester and camphor oil;

Blend-1: 80: 20 of camphor oil and neem oil methyl ester.

Blend- 2: 60:40 neem oil methyl ester and camphor oil.

Weighed the oils were combined with a magnetic stirrer at 500 rpm in a mixture with a blend of 30 minutes at room temperature to guarantee total homogenization. The ready blends were described in physical appearance, odor, specific gravity, acid value and stability.

2.2.3 Characterization of Emulsifier:

The emulsifier was characterized by evaluating their essential physicochemical properties, including appearance, specific gravity, hydrophilic-lipophilic balance (HLB), and surface-active characteristics.

2.2.4 Preparation of Microemulsions:

Pseudo-ternary phase diagrams were constructed at room temperature (25 +- 2degC) using the water titration method to identify regions of microemulsion formation. The three components of the phase diagrams were: (1) oil phase (camphor oil-neem oil methyl ester blend), (2) surfactant (ethoxylated vegetable oils), and (3) aqueous phase (deionized water). The procedure involved mixing oil and surfactant in varying weight ratios from 0:10 to 10:0 in increments of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, and 10:0. For each oil-to-surfactant ratio, deionized water was added dropwise under constant magnetic stirring at 500 rpm using a burette until either a clear, transparent, isotropic solution transitioned to a turbid dispersion, or until the system could not incorporate additional water. The exact amount of water added at the point of turbidity onset was recorded. Clear, transparent, and isotropic single-phase regions in the pseudo-ternary phase diagrams were identified as microemulsion zones. The boundaries between microemulsion and non-microemulsion regions were carefully mapped by gradually increasing water content and noting the transition from clarity to turbidity.

2.2.5 Characterization of Microemulsions:

The prepared microemulsions were characterized to determine their physicochemical properties and stability behavior. The formulations were visually examined at 25 degC to assess clarity, homogeneity, and the absence of phase separation or turbidity. The pH of each formulation was measured in triplicate using a calibrated pH meter (Equiptronics Model EQ 621, India). Viscosity was determined using a Brookfield viscometer, while droplet size and polydispersity index (PDI) were analyzed by Dynamic Light Scattering (DLS) (Mastersizer 3000 Hydro, Malvern Panalytical, UK). The electrical conductivity of each sample was measured at 25 degC using a conductivity meter (LMCM20, Labman Scientific Instruments, India) to distinguish between oil-in-water (O/W) and water-in-oil (W/O) systems. To assess thermodynamic stability, the formulations were stored at room temperature for 30 days and periodically evaluated for changes in particle size, pH, conductivity, and viscosity. Additionally, samples were subjected to centrifugation at 3,000 rpm for 30 minutes to investigate their resistance to phase separation and confirm long-term stability.

2.2.6 Antimicrobial Activity Evaluation:

Antimicrobial efficacy was evaluated according to EN 1040:2005 standard method against two bacterial strains: Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 10536. Bacterial cultures were grown in nutrient broth at 37 +- 1degC for 24 hours, and inocula containing approximately 105 CFU/mL were prepared. Test solutions at 100 mL/L concentration were mixed with bacterial suspensions and exposed for 5 minutes at 25 +- 2degC. After neutralization using appropriate neutralizing agents, surviving organisms were enumerated using the standard plate count method. Log reduction and percentage reduction values were calculated to assess antimicrobial efficacy.

3. RESULT:

3.1 Characterization of Neem oil methyl ester and camphor oil

Table 1: Physicochemical parameters of Neem oil methyl ester

Sr.no	Parameter	Neem oil methyl ester
1	Physical appearance	Clear Yellow liquid
2	Specific Gravity	0.870
3	Acid Value	0.12
4	Iodine Value	68.3
5	Saponification value	192

Table -2: Physicochemical parameters of camphor oil

Sr.no	Parameter	Camphor oil
1	Physical appearance	Clear Yellow liquid
2	Specific Gravity	0.890
3	Odour	Characteristic camphoraceous
4	Optical rotation (°)	+ 6 °
5	Refractive index (25 °C)	1.471

Table -3: Physicochemical parameters of camphor oil & Neem oil methyl ester Blend

Sr.no	Parameter	BLEND -1 Camphor oil & Neem oil methyl ester Blend (80 :20)	BLEND -2 Camphor oil & Neem oil methyl ester Blend (60:40)
1	Physical appearance	Clear Yellow liquid	Clear Yellow liquid
2	Odor	Characteristic Strong camphoraceous	Characteristic mild camphoraceous
3	Specific Gravity	0.890	0.885
4	Acid Value	0.1	0.1
5	Stability	Stable	Stable

Table -4:  physicochemical parameters of Surfactant

Sr.no	Parameter	Castor oil ethoxylated   35 moles	Jatropha oil ethoxylated 15 moles	Jatropha oil ethoxylated 20 moles
1	Physical appearance	Pale yellow clear liquid	Clear yellow Viscous liquid	Clear yellow Viscous liquid
2	pH (5% solution)	6.8	6.7	6.9
3	Saponification value	64	136	105
4	Moisture content	0.41	0.5	0.55
5	HLB value	12.5	9.7	11.7
6	Surface tension	40.35	44.32	41.44

Figure 1  Ternary Diagram: 80:20 Oil Blend HLB 9.7              Figure 2 Ternary Diagram: 80:20 Oil Blend HLB 11.7

Figure 3 Ternary Diagram: 80:20 Oil Blend HLB 12.5              Figure 4 Ternary Diagram: 60:40 Oil Blend HLB 9.7

Figure 5 Ternary Diagram: 60:40 Oil Blend HLB 11.7             Figure 6 Ternary Diagram: 60:40 Oil Blend HLB 12.5

Table -5: - Microemulsion with different HLB Physical parameter

Sr.no	Formulation	HLB	Type of emulsion	pH	Density	Conductivity	Particle size
1	Blend -1 CO -1	HLB 12.5	O/W	7.23	1.012	294.50	81.90
2	Blend -1 CO -2	HLB 12.5	W/O	7.16	1.013	90.21	100.3
3	Blend -1JO -3	HLB 9.7	O/W	7.31	1.011	310.40	189.2
4	Blend -1JO -4	HLB 9.7	W/O	7.34	1.014	71.25	150.30
5	Blend -1 JO -5	HLB 11.7	O/W	7.15	1.012	330.35	134.2
6	Blend -1 JO -6	HLB 11.7	W/O	7.31	1.013	75.64	121.2
7	Blend -2 CO -1	HLB 12.5	O/W	7.12	1.012	320.3	91.23
8	Blend -2 CO -2	HLB 12.5	W/O	7.09	1.014	82.4	98.24
9	Blend -2 JO -3	HLB 9.7	O/W	7.32	1.012	330.31	155.3
10	Blend -2 JO -4	HLB 9.7	W/O	7.21	1.013	81.27	143.2
11	Blend -2 JO -5	HLB 11.7	O/W	7.17	1.011	340.15	111.1
12	Blend -2 JO -6	HLB 11.7	W/O	7.21	1.012	85.64	91.23

Table -6: - Microemulsion Centrifuge stability data

Sr.no	Formulation	HLB	Centrifuge stability Before	Centrifuge stability After 30 days
1	Blend -1 CO -1	HLB 12.5	Stable	Stable
2	Blend -1 CO -2	HLB 12.5	Stable	Stable
3	Blend -1JO -3	HLB 9.7	Stable	Stable
4	Blend -1JO -4	HLB 9.7	Stable	Stable
5	Blend -1 JO -5	HLB 11.7	Stable	Stable
6	Blend -1 JO -6	HLB 11.7	Stable	Stable
7	Blend -2 CO -1	HLB 12.5	Stable	Stable
8	Blend -2 CO -2	HLB 12.5	Stable	Stable
9	Blend -2 JO -3	HLB 9.7	Stable	Stable
10	Blend -2 JO -4	HLB 9.7	Stable	Stable
11	Blend -2 JO -5	HLB 11.7	Stable	Stable
12	Blend -2 JO -6	HLB 11.7	Stable	Stable

Table 7: - Antimicrobial activity Data

Sample Identification	Test Organism	Count of test organism			Antimicrobial activity
		Initial Count (CFU/ml)	After Exposure
			CFU/ml	Log	Log Reduction	Percentage Reduction
Blend -1 CO -1	Staphylococcus aureus	2.10 x 10^5Log =5.32	2.37x10^2	2.37	2.94	99.89
Blend -1 CO -1	Escherichia coli	2.24 x 10^5 Log=5.35	2.50x10^2	2.39	2.95	99.89
Blend -1 JO -5	Staphylococcus aureus	2.24 x 10^5Log=5.35	<10	<1	>4.35	>99.99
Blend -1 JO -5	Escherichia coli	2.08 x 10^5 Log=5.31	2.52x10^2	2.40	2.91	99.88
Blend -2 CO -1	Staphylococcus aureus	1.90 x 10^5Log=5.27	1.00x10^2	2.00	3.27	99.95
Blend -2 CO -1	Escherichia coli	2.10 x 10^5Log =5.32	2.37x10^2	2.37	2.94	99.89
Blend -2 CO -2	Staphylococcus aureus	2.08 x 10^5 Log=5.31	2.52x10^2	2.40	2.91	99.88
Blend -2 JO -2	Escherichia coli	2.08 x 10^5Log=5.31	2.60 x10^2	2.41	2.90	99.87

4. DISCUSIION:

The current paper has managed to prove that it is indeed possible to create purely bio-based antimicrobial microemulsion systems that are both environmentally friendly and useful in terms of antimicrobial activity. The detailed description of the neem oil methyl ester and camphor oil gave the necessary groundwork data towards formulation optimization. The value of specific gravity of neem oil methyl ester and camphor oil (0.870 and 0.890 respectively) is used to determine the compatibility of the two substances in that particular blend and the specific gravity of this blend (0.890 and 0.885 respectively) is the result of this compatibility. The acid values (0.12 neem oil methyl ester and 0.1 both blends) confirm the chemical stability and quality of the oil components which is essential to preserve shelf-life of formulations as well as antimicrobial activity performance. The use of ethoxylated vegetable oils as the surfactants is a strategic decision that is within the principles of green chemistry. Castor oil ethoxylate (HLB 12.5) and jatropha oil ethoxylates (HLB 9.7 and 11.7) were suitable in terms of surface-active properties, where the surface tension values were between 40.35 and 44.32 mN/m, which is sufficient to have interfacial activity to form and stabilize microemulsions. The HLB variation facilitated the ease with which the formulation space could be explored systematically and the fact that both O/W and W/O microemulsion systems could be optimized to give flexibility to meet different application needs.

The pseudo-ternary phase diagram experiments showed clear-cut microemulsion phases of all the tested mixtures, proving the thermodynamic compatibility of the chosen components. The effectiveness of the system based on the methyl ester-camphor oil-ethoxylated vegetable oil shows the strength of the system due to the successful development of twelve stable formulations with different ratios of oil blends and HLB. The particle size analysis showed that droplet sizes were 81.90 nm to 189.2 nm in size, which is the size range of microemulsions (usually 10-200 nm). It is worth noting that the HLB 12.5 formulations were always able to generate smaller particle sizes (81.90-100.3 nm range) and this can be explained by the fact that the higher the hydrophilicity of the castor oil ethoxylate the more effective the curvature in the oil-water interface and formation of finer droplets.

The measurements of conductivity successfully differentiated between O/W and W/O systems with O/W microemulsions recording a range of 294.50-340.15 uS/cm in corresponding conductivity owing to continuous aqueous phase, whereas W/O systems had a range of 71.25-90.21 uS/cm in accordance with the non-conductive continuous oil phase. The formulations were kept at almost neutral pH (7.09-7.34), which is very beneficial towards the users and compatibility with different surface materials. The values of density (1.011-1.014 g/cm3) showed little variation with all the formulations indicating that there was no significant effect of HLB change on the bulk physical properties. The stability test was excellent as all the twelve formulations still retained their original attributes after storage time of 30 days in room temperature and none of the formulations phase-separated after centrifugation at the rate of 3,000 rpm over 30 minutes. Such thermodynamic stability is specifically important when using complex multi-component systems and proves the suitability of the chosen surfactant concentrations and the ratios of oil to surfactant. These formulations are also strongly indicated by their stability results to be robust enough to be subjected to commercial development and real-world application situations where temperature variations and mechanical stress can be experienced.

The antimicrobial efficacy test produced very encouraging data that affirm the basis of the hypothesis of this study. The formulations used against Staphylococcus aureus, a prototype Gram-positive pathogen and frequent cause of healthcare-associated infections and skin infections, displayed log reductions between 2.91 and more than 4.35 with the Blend-1 JO-5 formulation showing outstanding performance with 100 percent elimination of organisms detected (<10 CFU/mL of initial counts of 2.24x105 CFU/mL). In comparison to Escherichia coli, a paradigm Gram-negative bacterium and one of the indicators of fecal pollution, the log reductions were between 2.90 and 2.95, with the percentage reductions of 99.87 and 99.89%. It is of particular interest that the Blend-1 JO-5 (80:20 camphor oil to neem oil methyl ester blend with HLB 11.7 jatropha oil ethoxylate) is better performing than the other ones. This is probably due to a number of factors. The increased components of camphor oil (80) present high concentrations of active monoterpenes such as camphor, 1, 8 -cineole, and a-pinene that are known to disrupt bacterial cell membranes due to their highly lipophilic property and capability to penetrate and destabilize membrane structures. The middle HLB figure of 11.7 could be a good compromise between hydrophilic and lipophilic properties which allows effective delivery of antimicrobial compounds to bacterial surfaces and an adequate interfacial concentration of active ingredients. The size of the particle used in this formulation (134.2 nm) lies in the gold mean of the observed systems, which may provide a beneficial compromise between surface area and delivery of antimicrobials and stability to resist Ostwald ripening. The neem-camphor oil combination is probably multi-factorial and synergistic in terms of its antimicrobial actions. It has been reported that components of neem oil like azadirachtin and nimbin interfere with bacterial protein synthesis and disrupt the action of enzymes whereas the monoterpenes of camphor oil mostly act by disrupting membranes and causing oxidative stress. Such a combination of mechanisms, which address various cellular structures and metabolic processes, lowers the chances of developing resistance and improves the general antimicrobial activity. The solvent system of methyl ester could also help in antimicrobial effects by being able to solubilise effects which increase the bioavailability and delivery of the active phytochemical compounds to the microbial targets.

These differences in antimicrobial activity between different formulations indicate that oil blend ratios, HLB values and the type of microemulsion (O/W vs. W/O) should be carefully optimized to achieve maximum performance. The O/W formulations tended to have a little better performance which may be as a result of the increased release of antimicrobial compounds of the dispersed oil phase into the continuous aqueous phase where the bacteria cells are suspended during testing. Nevertheless, in certain usage cases, the benefits of W/O formulations can be demonstrated, e.g. when a residual level of antimicrobial activity is needed, or when water evaporation would be problematic. These bio-based microemulsions have a number of unique benefits as compared to traditional synthetic disinfectants. To begin with, they remove the environmental persistence issues that are attributed to quaternary ammonium compounds and chlorine-based disinfectants because all of the components are easily biodegradable. Second, active ingredients have a natural source requiring less risks of skin sensitization and respiratory irritation that are often characteristic of the synthetic chemicals. Third, natural anti microbials have multi-target mechanisms, which can be used to overcome the issue of increasing antimicrobial resistance. Fourth, the renewable feedstocks are in line with the idea of the circular economy and decrease the reliance on petroleum-based materials.

5. CONCLUSION:

The present study manages to show that completely bio-based microemulsion systems with neem oil methyl ester, camphor oil, and ethoxylated vegetable oils can be designed to offer effective antimicrobial activity to be used as a disinfect surface. By systematic exploration of oil blend ratios and surfactant HLB values twelve stable formulations were prepared and fully characterized. All the formulations were found to have good physicochemical characteristics, with the particle sizes in the nanometre range (81.90-189.2 nm), near-neutral pH values, which were favourable to handle safely and excellent thermodynamic stability maintained throughout the 30 days storage, as well as centrifugation stress. The antimicrobial efficacy test showed a high bactericidal effect on the Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria with the log reduction between 2.90 and >4.35 and percentage reduction between 99.87 and >99.99 on the bacteria even after 5 minutes of exposure. The effectiveness of the Blend-1 JO-5 formulation (80:20 camphor oil to neem oil methyl ester with HLB 11.7) is a higher level of success compared to standard synthetic formulations and, therefore, indicates that bio-based systems can be as antimicrobial effective as commercial synthetic counterparts when component ratios and surfactant properties are optimized.

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Received on 06.11.2025     Revised on 20.11.2025

Accepted on 26.11.2025 Published on 28.11.2025

Available online from December 31, 2025

Research J. Engineering and Tech. 2025; 16(4):153-161.

DOI: 10.52711/2321-581X.2025.00015

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