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Rev. biol. mar. oceanogr. 50(3): 545-561

Article


Seaweeds agarophytes and associated epiphytic bacteria along Alexandria coastline, Egypt, with emphasis on the evaluation and extraction of agar and agarose

Hassan A.H. Ibrahim1, Ehab A. Beltagy1, Nihal G. Shams El-Din2, Gehan M. El Zokm3, Amany M. El-Sikaily4 and Gehan M. Abu-Elela1

1Microbiology Department, National Institute of Oceanography and Fisheries (NIOF), Kayet Bay, El-Anfoushy, Alexandria, Egypt
2Hydrobiology Department, NIOF, Kayet Bay, El-Anfoushy, Alexandria, Egypt
3Marine Chemistry Department, NIOF, Kayet Bay, El-Anfoushy, Alexandria, Egypt
4Marine Pollution Department, NIOF, Kayet Bay, El-Anfoushy, Alexandria, Egypt

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A survey of seaweeds along Alexandria coastline was carried out to choose a suitable agarophyte for extraction and evaluation of the agar and agarose substances, in addition to estimate and identify the epiphytic bacteria associated with these seaweeds which are capable of secreting package of hydrolytic enzymes and hence degrading algal cell walls successfully. A total of 13 algal samples were collected during spring 2012. There were 2 Rhodophytes species; Gelidium crinale and Pterocladiella capillacea, which can be exploited for agar and agarose production. Nine dominant bacterial isolates were associated with the different algal samples; they were identified at genus level as; Alcaligenes sp., Bordetella sp., Acinetobacter sp., Pseudomonas sp.1, Pseudomonas sp.2, Pseudomonas sp.3, Flavobacterium sp., Vibrio sp. and Vigribacillus sp. The most superior species able to secrete a package of degrading enzymes was Vigribacillus sp. that was isolated from P. capillacea harvested from Western Harbor. The total carbohydrate, lipid and protein contents were determined in both P. capillacea and its agar, and in Oxoid agar (a reference commercial material). Some metals (copper, cadmium, lead, zinc, nickel, chrome, ferrous, manganese and arsenic) were also estimated in the 3 mentioned samples. The gel strength, gelling temperature and melting temperature besides the clarity and viscosity of extracted and Oxoid agars showed different patterns. The sulphate content of the extracted agar was slightly higher than that of Oxoid agar, while the pyruvate content showed inverse pattern. The extracted agar FTIR spectrum indicated methylated group, which proved that the agar extracted from P. capillacea is a highly methylated polysaccharide resulting in high gellation.

Key words:  Epiphytic bacteria, agarophyte, agar, agarose

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