Eleven lactobacilli strains of the lactobacilli (Table 1) deposited in the laboratory collection in the form of monocultures freeze-dried or frozen were used in our research. Cultures of each bacterial strain were conducted in three independent experiments. First, the cultures were revived in the MRS (de Mann, Rogosa, and Sharpe) broth supplemented with Tween 80™ (Sigma-Aldrich) in portions of 50 mL (incubation at 37°C for approx. 12 h). Tween 80™ is known to influence membrane fluidity and potentially impact fatty acid synthesis in lactobacilli (Al-Naseri et al., 2013; Zotta et al., 2017b; Reitermayer et al., 2018). Subsequently, the cultures were inoculated onto the surface of three parallel MRS agar plates with Tween 80™ and three parallel MRS agar plates without Tween 80™ (in two independent replicates for each growth medium). Cultures were incubated at 37°C for 24 h under anaerobic conditions. Anaerocult™ A (Merck) was used to produce an anaerobic milieu in the anaerobic jar™ (Merck). Anaerocult™ A is recommended for the cultivation of obligatory and facultative anaerobes. To minimize growth phase variation, we carefully harvested cells for biomass collection from the defined center sector of each plate using the secondary inoculum. This ensured a representative sample of the cultured population for fatty acid analysis (Asadi et al., 2015).

The fatty acids were extracted from the entire bacterial biomass according to recommendations (Haack et al., 1994; Buyer, 2002; Kankaanpaa et al., 2004). Each bacterial biomass sample was prepared for analysis and analyzed in two replicates. The chromatographic separation of fatty acid methyl esters was carried out by gas chromatography coupled with mass spectrometer (GC-MS QP 2010 Shimadzu, Shimadzu Corporation, Japan) using polar column 007-23-30-0.2F (30 m × 0.25 mm × 0.20 μm; Quadrex, Quadrex Corporation, United States). The sample was injected under a split ratio of 1:25 at the dispenser temperature equal to 230°C. The chromatographic separation was conducted in the following conditions: Initial temperature of column of 60°C, 2 min isotherm, the temperature increase of 4°C/min to 220°C, 10 min isotherm. The carrier gas was helium with a flow rate of 0.37 mL/min. The following detector conditions were used: Temperature of the ion source of 200°C, temperature of the line connecting GC with MS of 220°C, detector voltage of 1.45 kV, and quadrupole filter sweep in a range 50-400 m/z. The following standards were used for identifying fatty acids: oleic acid (Sigma Aldrich, United States), anteiso12-methyltetradecanoic acid (Sigma Aldrich, United States), 2-hydroxytetradecanoic acid (Sigma Aldrich, United States), nonadecanoic acid (Sigma Aldrich, United States), the BAME (bacterial acid methyl esters; Sigma Aldrich, United States), GLC-674 and GLC-617 (Nu-Chek-Prep., United States), and isomers of methyl esters of linoleic acid 18:2 (cis-9,trans-11 and trans-10,cis-12; Nu-Chek-Prep., United States). The composition of bacterial acid methyl esters (BAMEs) is presented in Supplementary Table 1S. In other cases of fatty acids (including lactobacillic acid), the comparisons were made with the literature data (Brondz, 2002; Christie et al., 2007; Montanari et al., 2010). The data obtained from GC-MS was analyzed using GCMS Solution v.2.50 (Shimadzu Corporation).

The statistical analysis was carried out using the statistical program Statistica v.10. The analysis of variance (ANOVA) was employed. In this study, ANOVA was complemented by Tukey’s test, conducted at a significance level of 0.05, to scrutinize the mutual influence of the factors and identify any statistically significant differences between them. Principal components analysis (PCA) was conducted to assess the relationship between fatty acid profiles and the presence or absence of Tween 80™ in the growth medium. In this case, PCA was used to identify the main components that influenced the variation in fatty acid profiles.

The determined fatty acid profile of L. rhamnosus GG, L. rhamnosus MB, and L. rhamnosus ATCC 4769 cells demonstrated the presence of 29 fatty acids after the incubation on the growth medium with Tween 80™ (Table 2). The strains of L. rhamnosus used in our study were characterized by an intense growth on the MRS agar without Tween 80™. The character of the growth of this species’ colonies was different from other lactobacilli species used for this study. The colonies on the line of loop movement were snow-white with characteristic papules and damming, and so obtaining the biomass required for the analysis was not difficult. Nineteen fatty acids were identified in the fatty acid profile of L. rhamnosus GG cells, while the presence of 21 fatty acids was noted in the case of L. rhamnosus MB and L. rhamnosus ATCC 7469 cells (Table 2).

By comparing the test strains of L. rhamnosus species acid, similarities were observed in the sequence fatty acid dominant in the fatty acid profile of the cells. The comparative analysis (conducted using Tukey’s test) of the share of all dominant fatty acids in the fatty acid profiles obtained from the biomass of all strains showed significant differences. The fatty acid profile of the L. rhamnosus GG strain was dominated (the share >10%) by palmitic (C16:0), dihydrosterculic (cycC19:0,cis-9,10), lactobacillic (cycC19:0,cis-10,11), and oleic (C18:1,cis-9,) fatty acids. Meanwhile, the fatty acid profile of the L. rhamnosus MB strain was dominated (the share >10%) by palmitic acid, dihydrosterculic acid (cycC19:0,cis-9,10), oleic acid, and cis-vaccenic fatty (C18:1,cis-11) acids. As for the fatty acid profile of L. rhamnosus ATCC 7469 strain, it was dominated by palmitic (C16:0), dihydrosterculic (cycC19:0,cis-9,10), lactobacillic (cycC19:0,cis-10,11), and cis-vaccenic acid (C18:1,cis-11) acids (the share >10%). Their contribution to the fatty acid profile changed significantly when Tween 80™ was eliminated from the growth medium. The only fatty acids whose proportion in the fatty acid profile did not change significantly were the following fatty acids: caproic (C10:0), anteiso-12-methyltetradecanoic (C15:0,anteiso), palmitoleic (C16:1,cis-9), and linoelaidic (C18:2,trans-9,trans-12) fatty acids. In general, removal of Tween 80™ from the growth medium resulted in a decrease in the proportion of 14 fatty acids in the fatty acid profile, both saturated and unsaturated fatty acids, and an increase in the proportion of 11 fatty acids in the profile of fatty acids, mainly unsaturated fatty acids. Of course, these changes were not observed in every L. rhamnosus strains tested. Consequently, this resulted in a significant reduction in the calculated the ratio dihydrosterculic acid (cycC19:0,cis-9,10)/lactobacillic acid (cycC19:0,cis-10,11) (St/Lb ratio) with the exception for the L. rhamnosus MB strain, the ratio oleic acid (C18:1,cis-9)/cis-vaccenic acid (C18:1,cis-11) (O/V ratio), and the ratio unsaturated acids/saturated fatty acids (U/S ratio). It is worth noting that removal of Tween 80™ from the growth medium resulted in a significant reduction in the proportion of total unsaturated fatty acids, including conjugated fatty acids (CLA), in the fatty acid profile, but also did not result in a complete change in the proportion of saturated fatty acids in the fatty acid profile.

Kankaanpaa et al. (2004) found that L. rhamnosus GG cells grown with Tween 80™ contained oleic (21.5%), cis-vaccenic (21.8%), dihydrosterculic (23.5%), and lactobacillic (2.1%) acids as major fatty acids, along with conjugated acids at about 3%. Bacteria produce unsaturated fatty acids with various functionalities de novo (Zhu et al., 2019). These modifications, along with other fatty acids, increase the fluidity of the cytoplasmic membrane through their specific structures (Kaneda, 1991). The ability of the strains to synthesize cis-vaccenic acid and convert it to lactobacillic acid is noteworthy, with minimal de novo synthesis of oleic acid, especially in the absence of Tween 80™. The presence of Tween 80™ appears to inhibit the FAS system, as suggested by (Zhang et al., 2020). Our study indicates that all strains produced vaccenic acid even under anaerobic conditions, which is significant since anaerobic conditions favor the anaerobic vaccenic acid pathway. This contrasts with aerobic conditions in L. casei N87, which enhance growth, metabolism, and stress tolerance, influencing vaccenic acid synthesis (Ianniello et al., 2016). Refrigerated storage before biomass extraction can increase the proportion of unsaturated fatty acids (Zhu et al., 2019), which helps maintain membrane fluidity and protein activity (Santivarangkna et al., 2008; Parsons and Rock, 2013). The absence of oleic acid stimulates lactobacillic acid synthesis, while its presence increases dihydrosterculic acid levels (Kankaanpaa et al., 2004). This adaptive modification in fatty acid composition helps control membrane fluidity, aiding bacterial stress defense (Beal et al., 2001; Murga et al., 2001; Montanari et al., 2010; Pawar and Aranha, 2022). Environmental factors significantly influence unsaturated fatty acid proportions in lactobacilli membranes (Zotta et al., 2017a; Fonseca et al., 2019), with oxygen availability playing a crucial role (López de Felipe, 2023). Under aerobic conditions, lactobacilli can convert palmitoleic acid to cis-vaccenic acid (Cronan, 2002; Schujman and Mendoza, 2008; Jimenez et al., 2023). Corcoran et al. (2007) noted a rise in certain acids in L. rhamnosus GG cells when exposed to oleic acid (C18:1,cis-9). Our research found that adding oleic acid via Tween 80™ increased dihydrosterculic acid (cycC19:0,cis-9,10), oleic acid (C18:1,cis-9), and conjugated fatty acids, while reducing palmitic (C16:0) and stearic (C18:0) acids. Furthermore, L. rhamnosus GG, L. rhamnosus MB, and L. rhamnosus ATCC 7469 cells cultured without Tween 80™ showed lactobacillic acid (cycC19:0,cis-10,11) dominance in their fatty acid profiles. This difference is likely due to the lack of separation of cyclic acids in the Corcoran et al. (2007) study.

The identified fatty acid profile of L. casei 393, L. casei 431, and L. paracasei subsp. paracasei MB grown on MRS agar with Tween 80™ contained 29 and 27 fatty acids for L. casei and L. paracasei, respectively (Table 3). The predominant fatty acids in the fatty acid profile of the first of these strains were: palmitic acid (C16:0), dihydrosterculic acid (cycC19:0,cis-9,10), lactobacillic acid (cycC19:0,cis-10,11), and cis-vaccenic acid (C18:1,cis-11). Meanwhile, fatty acids such as palmitic acid, oleic acid (C18:1,cis-9), cis-vaccenic acid (C18:1,cis-11), and dihydrosterculic acid (cycC19:0,cis-9,10) were found to be dominant for the fatty acid profile of L. casei 431. On the other hand, dominant fatty acids in the L. paracasei subsp. paracasei MB fatty acid profile included oleic acid (C18:1,cis-9), dihydrosterculic acid (cycC19:0,cis-9,10), and palmitic acid (C16:0). While dihydrosterculic acid (cycC19:0,cis-9,10) could potentially be used to differentiate between L. casei and L. paracasei subsp. paracasei MB, the high proportion observed in this study might be due to stress experienced by the bacteria during growth (Rouch et al., 2002; Wu et al., 2020; Klein et al., 2022). Cyclic fatty acids, including dihydrosterculic acid (cycC19:0,cis-9,10), are known markers of stress in LAB. Further studies are needed to investigate the influence of growth conditions on the fatty acid profile of L. paracasei subsp. paracasei MB and confirm its potential as a differentiating factor. L. casei and L. paracasei grown without Tween 80™ displayed altered fatty acid profiles compared to cultures with Tween 80™. Notably, the absence of oleic acid (C18:1,cis-9) triggered cis-vaccenic (C18:1,cis-11) and lactobacillic acid (cycC19:0,cis-10,11) synthesis. Total saturated fatty acids, especially iso-13-methyltetradecanoic (C15:0,iso) and stearic (C18:0) acids, increased in bacteria lacking Tween 80™, although this effect was not universal. Conversely, unsaturated fatty acid content and the U/S ratio decreased without Tween 80™. Interestingly, total CLA and St/Lb and O/V ratios also significantly declined. These changes in L. casei and paracasei are distinct from those observed previously inL. rhamnosus.

We observed significant differences in the proportions of saturated, unsaturated, and cyclic fatty acids compared to previous studies (Rizzo et al., 1987; Kankaanpaa et al., 2004; Machado et al., 2004; Liong and Shah, 2005; Corsetti et al., 2010; Rodrigues et al., 2012). Notably, our findings revealed substantial levels of dihydrosterculic and lactobacillic acids, cyclic derivatives of oleic and vaccenic acids, respectively. These results contrast with some prior studies that may have missed these cyclic acids due to separation and detection challenges (Machado et al., 2004; Liong and Shah, 2005). For L. casei, our dominant fatty acids included dihydrosterculic and lactobacillic acids, alongside palmitic acid. This aligns with the findings of Rizzo et al. (1987) who reported palmitic, octadecenoic, and cyclopropane acids as the major components in L. casei ATCC 393. However, some discrepancies exist, such as the presence of palmitoleic acid in Machado et al. (2004) which we did not observe. These differences could be attributed to various factors, including strain variations and growth conditions. While comparisons for L. paracasei subsp. paracasei MB were limited due to a scarcity of data specifically for this subspecies, it’s important to acknowledge that the L. casei group taxonomy has undergone revisions in recent years. Some strains previously classified as L. casei may now be identified as L. paracasei. Future studies that incorporate a wider range of Lactobacillus species, including recently reclassified members of the casei group, along with standardized protocols, would offer valuable insights into the influence of growth media components on bacterial fatty acid composition.

The fatty acid profile of bacterial biomass of L. fermentum ATCC 9338 and L. reuteri DSM 17938 cultured on growth medium with Tween 80™ was characterized by the presence of 27 and 28 fatty acids, respectively (Table 4). We demonstrated that L. fermentum ATCC 9338 was characterized by the share of palmitic (C16:0), oleic (C18:1,cis-9), lactobacillic (cycC19:0,cis-10,11), cis-vaccenic (C18:1,cis-11), and dihydrosterculic fatty (cycC19:0,cis-9,10) acids, while L. reuteri DSM 17938 by palmitic, cis-vaccenic (C18:1,cis-11), dihydrosterculic (cycC19:0,cis-9,10), and lactobacillic (cycC19:0,cis-10,11) acids. Each of these strains demonstrated the ability to synthesize vaccenic and lactobacillic (cycC19:0,cis-10,11) acids, which were in a pool of dominant fatty acids. We also demonstrated the presence of oleic acid (C18:1,cis-9) and its cyclic derivative, dihydrosterculic acid (cycC19:0,cis-9,10) (Table 4). L. fermentum ATCC 9338 and L. reuteri DSM 17938 showed excellent growth on MRS agar without Tween 80™. The fatty acid profile of the first of these strains contained 20 fatty acids, while the second strain was characterized by 22 fatty acids. Removal of Tween 80™ from the growth medium resulted in statistically significant changes in the fatty acid profile of bacterial strains: an increase in the share of 8 fatty acids (5 unsaturated fatty acids and 3 saturated fatty acids) and a decrease in the share of 11 fatty acids (4 saturated fatty acids and 7 unsaturated fatty acids). This significantly reduced the calculated ratios of O/V and U/S, but increased the calculated St/Lb ratio. It is also worth noting that the changes observed were not the same across all bacterial strains tested, which, as with the lactobacilli strains discussed previously, allows for some differentiation.

Our study confirmed previous findings (Johnsson et al., 1995) that Tween 80™ significantly alters the fatty acid profile of L. fermentum. Oleic (C18:1,cis-9) and dihydrosterculic (cycC19:0,cis-9,10) acids, undetectable without the surfactant, became enriched upon its addition. This effect occurred without affecting growth rate, suggesting independent processes. Furthermore, our results aligned with Rizzo et al. (1987) regarding the overall fatty acid composition of L. fermentum, highlighting the consistency of this profile across strains.

Taranto et al. (2006) determined the dominant fatty acid in L. reuteri CRL 1098 to be palmitic acid (57.7%). Our study found a similar proportion of palmitic acid (40.07%) in L. reuteri cells, suggesting a relatively consistent fatty acid profile for this species. Similar results were observed for stearic acid (3.86% and 3.28%, respectively) and the ratio of oleic acid (C18:1,cis-9) to cis-vaccenic acid (C18:1,cis-11) ratio (0.70% and 0.62%). Comparison of cyclic acids was difficult due to limitations in the cited study (Taranto et al., 2006). The ability of L. reuteri strains to synthesize CLA from linoleic acid (C18:2,cis-9,cis-12) has been demonstrated previously (Jenkins and Courtney, 2003; Hernandez-Mendoza et al., 2009; Macouzet et al., 2010). Our study confirmed CLA synthesis by L. reuteri DSM 17938 at a level comparable to other strains. The dominant CLA profile was cis-9,trans-11-octadecadienoic acid, and the strain exhibited the ability to synthesize CLA even without added oleic acid. Lactic acid bacteria possess the ability to transform unsaturated fatty acids in their conjugated form (i.e., CLA) (Kishino et al., 2002; Lin et al., 2002; Lin et al., 2003; Ogawa et al., 2005; Lin, 2006).

Our study examined three strains of L. plantarum, all of which exhibited efficient growth on MRS agar with or without Tween 80™. Interestingly, the fatty acid profiles of L. plantarum 299v and L. plantarum B.01149cultured on growth medium with Tween 80™ exhibiting profiles with 24 fatty acids, and B.01834 exhibiting a 24-fatty acid profile. Cultivation on growth medium with the addition of Tween 80™ resulted in the fatty acid profile of all three strains examined being dominated by palmitic acid (C16:0), dihydrosterculic acid, cis-vaccinic acid and lactobacillic acid (cycC19:0,cis-10,11), with the involvement of the last two of these fatty acids differentiating the strains examined (Table 5). Removal of Tween 80™ from the growth medium resulted in a decrease in the share of 11 fatty acids (4 saturated and 7 unsaturated) in the fatty acid profile and an increase in the share of 9 fatty acids (6 saturated and 3 unsaturated) in the fatty acid profile. It is also worth mentioning that the overall contribution of CLA to the fatty acid profile of the tested strains was also statistically reduced due to the removal of Tween 80™ from the growth medium. As a result, the proportion of total saturated and unsaturated fatty acids in the fatty acid profile increased significantly in some bacterial strains. Instead, a significant increase in the St/Lb ratio and a significant decrease in the O/V ratio were observed.

We identified discrepancies with Johnsson et al. (1995) regarding oleic acid (C18:1,cis-9) and lactobacillic acid (cycC19:0,cis-10,11) production by L. plantarum 2004. Our strains displayed a dominance of lactobacillic acid (11.02%–14.46%) and lower levels of oleic acid (up to 4.18%) compared to their findings. We attribute these differences to potential limitations in their methodology, such as sample size and incubation temperature. Our results for strains cultured without Tween 80™ showed a high proportion of palmitic acid (52.82%–54.78%), aligning with Rozès and Peres (1998). Both studies highlighted the prominence of C18:1 and cyclic C19:0 acids, although the specific compositions were not identical. Similarly, Russell et al. (1995) reported palmitic acid dominance, but stearic acid (C18:0) was not a major component in our analysis. These variations likely stem from differing incubation temperatures and analytical methods. Rizzo et al. (1987) identified palmitic (C16:0), cis-vaccenic (C18:1,cis-11), and cyclic C19:0 acids in L. plantarum ATCC 14917. However, their classification of the latter solely as lactobacillic acid (cycC19:0,cis-10,11) might not account for all possible isomers. L. plantarum’s ability to produce dihydrosterculic acid (cycC19:0,cis-9,10), as demonstrated by Johnsson et al. (1995), supports this notion. Our findings support this notion, revealing the presence of both lactobacillic (cycC19:0,cis-10,11) and dihydrosterculic (cycC19:0,cis-9,10) acids. Our research confirms the ability of L. plantarum strains to synthesize CLA (conjugated linoleic acid) from various substrates, as reported in previous studies (Ogawa et al., 2005; Kishino et al., 2009; Corsetti et al., 2010; Rodríguez-Alcalá et al., 2011). Studies by Kishino et al. (2009) CLA levels were significantly higher in cultures supplemented with Tween 80™ (1.67%–2.21%) compared to those without (0.16%–0.19%). The two predominant CLA isomers identified (cis-9,trans-11 and trans-10,cis-12) are consistent with Rodriguez-Alcalá et al. (2011). This study highlights the variability in fatty acid profiles of L. plantarum strains and emphasizes the need for standardized methodologies for accurate comparisons. We confirm the prevalence of palmitic (C16:0) and C18:1/cyclic C19:0 fatty acids, with lactobacillic acid (cycC19:0,cis-10,11) as the dominant cyclic form. Additionally, our findings support L. plantarum’s ability to produce CLA, with levels influenced by the presence of Tween 80™.

Fatty acids play a crucial role in the physiology and metabolism of lactobacilli. Their composition can influence various aspects of lactobacilli growth, function, and interaction with the environment. Understanding the fatty acid profiles of lactobacilli can provide valuable insights into their metabolic capabilities and potential applications. Of course, the fatty acid composition of lactobacilli can vary significantly depending on the strain and growth conditions. Principal components analysis revealed that growth medium supplementation with Tween 80™ significantly affected the fatty acid profiles of mesophilic lactobacilli strains, particularly the share of oleic acid (C18:1,cis-9), cis-vaccenic acid (C18:1,cis-11), lactobacillic acid (cycC19:0,cis-10,11), and dihydrosterculic acid (cycC19:0,cis-9,10). In general, the values of the first two principal components of the PCA statistical analysis of 57.53% are not too high and indicate that they do not fully explain the variability of the original data set. Nevertheless, the first two principal components may be statistically significant for the variables we are interested in. The PCA gives a quick overview of the connection between the different factors and the samples within. It should be noted that the first main component, which is 57.53% of the model variation, divided the cases into two main groups: the fatty acid profiles obtained from the growth medium with Tween 80™ and without Tween 80™ (Figure 1A). The first principal component separated the cases into two main groups based on the growth medium with or without Tween 80™ (Figure 1A). Notably, some L. casei strains did not cluster together, suggesting a potential taxonomic misclassification or high variability within this group. The high share of oleic acid (C18:1,cis-9) and CLA was important for the separation of the bacteria cultured on the growth medium with Tween 80™, while linoelaidic (C18:2,trans-9,trans-12), palmitelaidic (C16:1,trans-9), and cis-vaccenic (C18:1,cis-11) acids were important in case of growth medium without Tween 80™ (Figure 1B). This allowed for the separation of strains cultured on growth medium with Tween 80™ into two main groups: those cultured with Tween 80™ and cultured without Tween 80™. In contrast, no significant differentiation was observed for strains grown on the same growth medium without Tween 80™.

Recent taxonomic revisions suggest that some L. casei strains might be reclassified as L. paracasei (Ghosh et al., 2019). Unfortunately, we could not perform phylogenetic analysis on all our strains due to the lack of a genome sequence for C-431. Despite this uncertainty, we observed distinct fatty acid profiles among the three L. casei strains (potentially L. paracasei). However, further studies with a larger and well-characterized strain collection are necessary to confirm the discriminatory power of fatty acid profiles for differentiation between these closely related species.

The exact effects of the presence of Tween 80™ in the growth medium vary depending on the type of lactobacilli, but in general, Tween 80™ can increase saturated fatty acids and reduce unsaturated fatty acids. The presence of Tween 80™ in the growth medium generally increased the proportion of lactobacillic acid (cycC19:0,cis-10,11) in the fatty acid profile of all lactobacilli strains. This was due to the stimulation of the synthesis of lactobacillic acid (cycC19:0,cis-10,11) by lactobacilli cells in response to the absence of oleic acid (C18:1,cis-9) from Tween 80™. The presence of Tween 80™ in the growth medium had a mixed effect on the proportion of myristic acid (C14:0) and dihydrosterculic acid (cycC19:0,cis-9,10) in the fatty acid profile. In some lactobacilli strains, the proportion of myristic acid and dihydrosterculic acid (cycC19:0,cis-9,10) increased, while in other species, the proportion of myristic acid and dihydrosterculic acid (cycC19:0,cis-9,10) decreased. The presence of Tween 80™ in the growth medium significantly impacts the fatty acid profile of lactobacilli, generally increased the proportion of palmitic acid in the fatty acid profile of all lactobacilli strains. This was due to the incorporation of oleic acid (C18:1,cis-9) from Tween 80™ into the cell membranes of lactobacilli cells, which increased the demand for saturated fatty acids to maintain the fluidity of the cell membranes. While our data suggests a decrease in cis-vaccenic acid (C18:1,cis-11) in the fatty acid profile of all lactobacilli strains, further investigation is needed to elucidate the underlying mechanisms. Existing literature suggests that Tween 80™ might suppress early fatty acids synthesis, potentially affecting cis-vaccenic acid (C18:1,cis-11) production later in the growth cycle (Jacques et al., 1980; Zotta et al., 2017b; Reitermayer et al., 2018). Future studies employing time-course experiments could provide valuable insights into the dynamics of fatty acid biosynthesis and incorporation in the presence of Tween 80™, allowing for a more definitive understanding of potential competition or alternative pathways involved.