Analysis of Antimicrobial Activity and Chemical Composition of Seaweed Extract from F. vesiculosus

anglais. Marine macro algae possess many beneficial bioactive properties which can be of interest in various applications. Components of interest in seaweed are for instance sulfated polysaccharides, defined as fucoidan, with antimicrobial activities and polyphenols with antioxidative properties. This study analyses the antimicrobial effect of two extracts from Fucus vesiculosus and test their efficacy on five different test microorganisms. Both extracts derived from seaweed harvested outside the shore of Iceland in June 2012 respectively June 2015. The extract from seaweed collected 2015 was filtered to retain components larger than 100 kDa, and the extract derived from algae harvested in 2012 was unfiltered and thus contained components within the full range of size. Composition analysis on the seaweed extracts revealed that the composition of the seaweeds were fairly similar despite the different preparations. The filtered extract had a composition of 21.2 % carbohydrate, 6.1 % protein, 3.4 % phenol, 0.3 % fat and 31.5 % ash. The composition of the unfiltered extract were 18.0 % carbohydrate, 5.1 % protein, 5.3 % phenol, 0.6 % fat and 35.3 % ash. Turbidity tests for antimicrobial activity showed that high concentration of the unfiltered unsterilized extract was most efficient against growth of E. coli. The filtered extract autoclaved as powder met the acceptance criteria from the European pharmacopoeia for S. aureus and A. brasiliensis in the efficacy test. The filtered extract autoclaved in liquid form did not meet the criteria of acceptance for four microbes, and the results for A. brasiliensis were ambiguous. Because of the antimicrobial effects and antioxidative properties of F. vesiculosus interest has been shown to use the algae in food protection against oxidation of desired components and to prolong the time of storage.

anglais. The brown macroalgae, bladder wrack, which is abundant in mainly North Atlantic and Pacific Ocean, possess a variety of bioactivities. The bioactive polysaccharides, fucoidan, were of special interest in this study because of their properties towards bacteria and other microbes. Extracts from bladder wrack were produced to study the effects of seaweed on bacteria in a short term experiment and also to examine the long-term effects of seaweed on microbial growth. Analysis of the composition was performed to investigate the chemical variation between the two extracts. The cell-wall of bladder wrack contains bioactive compounds which help the plant to endure tough environmental conditions they are naturally subjected to; including varieties in sun exposure, water coverage and salinity. The bioactivity in seaweed is associated primarily with different polyphenols, proteins and poly-saccharides. Depending on when and where seaweed is harvested it can contain various concentrations of these bioactive components. In this study two substrates – one filtered extract containing components larger than 100 kDa and one unfiltered extract consisting of all-range sized compounds – from bladder wrack were used for the analyzes. Studies on the composition of the seaweed extracts revealed that the carbohydrate (21.2 % resp. 18.0 %) and protein (6.1 % resp. 5.1 %) content was slightly higher for the filtered extract than for the unfiltered. On the other hand, phenol (3.4 % resp. 5.3 %), fat (0.3 % resp. 0.6 %) and ash (31.5 % resp. 35.3 %) content were lower for the filtered extract than for the unfiltered. The short-term analysis of the algal impact on bacterial growth showed that the unfiltered extract were more efficient than the filtered. Tests were made on both unsterilized and autoclaved substrates. Extracts exposed to the heat treatment process demonstrated less effect against bacterial growth which indicated that active components were altered or destroyed in the sterilization process. Long-term exposure of algal extract autoclaved as powder on microbes showed bactericidal effect on S. aureus. The extract also showed inhibitory effect on the mold A. brasiliensis, although these results may be doubted due to visual observations of growth in the test tubes. The test did not demonstrate any effect for the remaining test organisms; E. coli, P. aeruginosa and C. albicans. Brown marine macroalgae has due to its antimicrobial and antioxidative properties potential to preserve food products and protect sensitive food components. Another application area may be within cosmeceutical production of for instance skincare products.