## 3 Results and Discussion
### Bioactivity of the Microalgae Extracts
#### 3.4.2 Antimicrobial Activity of Microalgae Extracts Against Bacteria  
Among the microbial extracts tested, _Nantochloropsis_ sp. exhibited the highest inhibitory effect, as evidenced by the lowest minimal inhibitory concentrations (MIC) against all bacteria strains assessed, with the exception of _Bacillus cereus_ (Table 6). Extracts of _Limospira_ sp., _Odontella_ sp., and _Lobsphaera_ sp. also showed notable antimicrobial activity, inhibiting the growth of all tested bacteria strains. In contrast, extracts from _Porphyridium_ sp. and _Dunaliella_ sp. did not show significant inhibitory effects at the concentrations tested. The extract of _Tetraselmis_ sp., although less potent than that of _Nannochloropsis_ sp., displayed inhibitory activity against all bacteria except _B. cereus_ (Table 6). [PERSON] et al. [58] prepared ethanolic extracts from several microalgae and reported the following MIC values (mg/mL): for _Dunaliella_ sp., 4.3 \(\pm\) 0.1 against _Pseudomonas aeruginosa_ and _Escherichia coli_, and \(>\)5 against _Staphylococcus aureus_; for _Nannochloropsis gaditana_, 3.4 \(\pm\) 0.2 against _E. coli_ and 4.5 \(\pm\) 0.6 against _S. aureus_; and for _Tetraselmis_ sp., 2.6 \(\pm\) 0.2 against _E. coli_ and 3 \(\pm\) 0.1 against _S. aureus_. [PERSON] et al. [59] determined the MICs of aqueous extracts from _Porphyridium cruentum_ and _Porphyridium aerugineum_. No inhibitory effect was observed against _B. cereus_, _E. coli_, or _Salmonella typhimurium_ for _P. aerugineum_, while the extract of _P. cruentum_ exhibited an MIC of 7.0 mg/mL against the same bacteria. Interestingly, _P. aerugineum_ showed enhanced efficacy against _Staphylococcus aureus_, with an MIC of 0.29 mg/mL. [PERSON] et al. [60] suggested that the antimicrobial activity of _Limospira_ sp. is associated with its content of pigments, polyphenols, fatty acids, and carbohydrates, and is particularly effective against _E. coli_. Similarly, they attributed the antimicrobial properties of _P. cruentum_ to pigments, polyphenols, and fatty acids (against _S. aureus_), and carbohydrates (against _E. coli_). [PERSON] et al. [61] reported that some strains of _Limospira platensis_ displayed potent antimicrobial activity, with MIC values ranging from 2-15 ug/mL against various fish pathogens, including species of _Bacillus_ and _Vibrio_. Additionally, _Dunaliella tertioleta_ displayed MIC values of 25 ug/mL and 50 ug/mL against certain _Staphylococcus_ spp. isolated from bovine and goat mastitis, respectively. These values were considerably lower than those found in the present study. As with antioxidant activity, the extraction method--including the choice of solvent, technique (e.g., maceration, sonication), and conditions (e.g., temperature, duration)--significantly influences the bioactivity of the resulting extracts. Moreover, the use of different bacterial strains introduces further variability. These factors may explain the discrepancies between the present findings and those previously reported in the literature. It is worth noting that for all tested bacteria strains, the minimum bactericidal concentration (MBC) was above 5 mg/100 uL, indicating that none of the microalgae extracts exhibited bactericidal effects at the tested concentrations.