3. Conclusions

Microalgae specie

118 Microalgal Biotechnology

Red algae Porphyridium aerugineum

Porphyridium sordidum

Porphyridium purpureum

Diatoms Asterionella glacialis

Attheya longicornis

Chaetoceros mulleri

Phaeodactylum tricornutum

Skeletonema costatum

Hapotophytes

Isochrysis galbana Chlorophyll a derivative:

Adapted from Falaise et al. [105].

Navicula delognei Transphytol ester

Antibacterial compound/Fraction Gram+ inhibition Gram

Pellet B. subtilis E. coli

Methanolic extracts B. subtilis E. coli

Scenedesmus sp. Ethanolic extracts S. aureus E. coli

Phycobiliproteins S. aureus

Whole cell S. aureus

Methanolic extracts S. aureus

Aqueous and organic extracts: chloroform: methanol (2:1). B. subtilis

Table 4. Antibacterial activity observed in different extracts from microalgae against human pathogens.

Rhodella reticulate Exopolysaccharides S. aureus

Unsaturated fatty acid-containing lepidic fractions (triglycerides and

docosa-pentaenoic acid (DPA))

Eicosapentaenoic acid [124]

Pheophytin a and chlorophyllide a

Hexadecatetraenoic and octadecatetraenoic acids

Palmitoleic and hexadecatrienoic acids (HTA)

Rhizosolenia alata Various organic solvent extracts: acetone, chloroform, chloroform: methanol (1:1), methanol: distilled water (4:1) and distilled water.

inhibition

P. aeruginosa

Pseudomonas fluorescens

Pseudomonas fluorescens

No effect [118]

E. coli [119]

No effect [120]

E. coli [121,

No effect [125]

P. aeruginosa [95]

Not tested [127,

S. typhimurium P. vulgaris

E. coli P. aeruginosa P. vulgaris S. typhi V. cholerae

122]

[123]

[126]

128]

Not tested [118]

S. pyogenes

B. cereus S. pyogenes

S. epidermidis M. luteus Sarcina sp.

MRSA

B. subtilis S. aureus

S. aureus S. epidermidis

B. cereus Bacillus Weihenstephanensis S. aureus S. epidermidis MRSA

B. subtilis, S. aureus

S. aureus

S. aureus Streptococcus faecalis S. pyogenes Micrococcus sp. Ref.

[45]

[116]

[116]

Cyanobacteria and microalgae have demonstrated a large potential as innovative sources of a large variety of bioactive compounds, such as fatty acids, antioxidants, antifreeze proteins and even antibiotics. While the characterization of substances as fatty acids is relatively wellestablished and straightforward, an information gap still remains in the elucidation of structures of antibiotics. Despite the fact that a variety of extracts obtained from microalgae biomass have demonstrated a clear antibiotic capacity, the structure of the molecules involved in the observed activity still remains unclear. There is a clear and almost unrevealed potential in the development of innovative nutraceutical and pharmaceutical industries based on cultivation of microalgae and cyanobacteria and their exploitation in the production of bioactive substances. Cyanobacteria and microalgae adapted to extreme environments for sure have an enormous potential that thorough bioprospecting approaches can help to unveil.
