## 3 Results and Discussion
### Antimicrobial Activity of GEs  
GEs derived from FAMEs of _C. echinulata, U. isabellina_, _N. gaditana_ SCOs, olive oil and EPA concentrate were tested against various human pathogens for their antimicrobial activity by the agar well diffusion method, which resulted in the formation of a zone of inhibition with a variable diameter (Table 4). GEs produced in this work, except for _U. isabellina_-GEs, showed moderate to strong inhibitory activity against all test organisms. In detail, _U. isabellina_-GEs showed weak antimicrobial activity (inhibition zone \(\approx\) 6 mm) against _S. typhimurium, P. aeruginosa_ and _S. aureus_. On the contrary, _C. echinulata_-GEs, _N. gaditana_-GEs and olive oil-GEs moderately inhibited all test organisms, while EPA-GEs showed the strongest antimicrobial activity against all test organisms, specifically against C. _allicans_ (20.0 \(\pm\) 0.1 mm), _B. subtilis_ (17.0 \(\pm\) 0.5 mm) and _S. aureus_ (17.0 \(\pm\) 0.2 mm). Finally, all GEs showed a higher antimicrobial activity against _C. albicans_ than against bacteria. It was shown that EPA-GEs were very effective against all bacteria tested and their activity can be attributed to their high EPA content. Furthermore, _C. echinulata_-GEs were more effective against pathogens compared with _U. isabellina_-GEs, probably due to the presence of GLA in the lipids of _C. echinulata_ in enhanced concentrations, which is known for its antimicrobial activity [25]. Previous research showed that GLA or EPA containing FA potassium salts were also effective against several Gram-positive and Gram-negative bacteria, but resistance was observed in some cases, such as in the case of _E. coli_ ATCC \begin{table}
\begin{tabular}{c c c} \hline \hline
**Entry** & **Source of FAMEs** & **Conversion (\%)** \\ \hline
1 & _Cumningham echinulata_ & 80.3 \(\pm\) 4.0 \\
2 & _Umbelopsis isabellina_ & 85.1 \(\pm\) 4.3 \\
3 & _Nannochloropsis galitana_ & 86.3 \(\pm\) 4.3 \\
4 & EPA concentrate & 99.1 \(\pm\) 5.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: GE synthesis by CA lipase in a solvent mixture consisting of 80% DMSO and 20% tert-amyl alcohol) utilizing FAMEs of different origins as substrates and for an incubation duration of 50 h.  
Figure 7: FTIR analysis of eicosapentaenoic acid (EPA) concentrate FAMEs and their glucose esters. 25922 [14]. The fact that this strain is sensitive to GLA or EPA containing GEs indicates that, in addition to esterified FA, the polar group plays a role in the activity of the various FA preparations. The MIC and MBC values were determined for selected pathogens (Table 5). All tested pathogenic strains were sensitive to all GEs, being inhibited at low MIC that ranged between 6.3 and 50 ug/mL, and destroyed at MBCs between 50 and 100 ug/mL. C. _echinulata_-GEs and EPA-GEs were more effective against all tested bacteria compared with _N. gaditana_-GEs and olive oil-GEs. The variability of the inhibitory effect found in this paper is in agreement with previous papers reporting that SEs exhibited a variable effect on different bacterial species [52; 53], while, depending on the conditions, SEs may inhibit Gram-negative [40; 54] or Gram-positive bacteria [55; 56]. Moreover, depending on the dose, SEs can be either bactericidal [57] or bacteriostatic [58]. [PERSON] et al. [59] reported that the inhibitory effect of SEs is dependent on the esterification level, type (e.g., the length of aliphatic chain) and number of esterified FAs on the sugar molecule and the nature of the carbohydrate. Furthermore, [PERSON] et al. [60] reported that the antimicrobial effects of fructose esters decreased as the aliphatic chain