Agar properties of two species of Gracilariaceae from the Gulf of California, Mexico

Abstract

Agar properties of two potentially commercial important seaweeds from the Gulf of California were studied. Maximum yield in Gracilaria vermiculophylla (45.7%) occurred during the summer months, coinciding with high water temperatures (31°C) whereas minimum yields (11.6%) were obtained during the coldest months of the year when populations of this species diminish in the bay. Gracilariopsis longissima showed two yield peaks, one in spring and another in fall, before the maximum and minimum seawater temperatures. Gel strength in native agar from the two species was low (<22.5 g cm −2 ) for most of the year.

Production and properties of agar from the invasive marine alga, Gracilaria vermiculophylla (Gracilariales, Rhodophyta)

“…Gel strength is defined as the pressure required to break the gel surface and is determined by assessing the stress for which a discontinuity (local maximum) is seen in the stress-strain curve. Apparent Young's modulus, E, was calculated from the stress-strain curve as described in Hilliou et al (2006a) without correction for sample buoyancy (Oakenfull et al 1989). Young's modulus is reported as 'apparent' since penetration test was employed in the determination (sensu Gregson et al 1999), as opposed to the 'real' Young's modulus which is obtained from uniaxial extension test.…”

Agar extraction process for Gracilaria cliftonii (Withell, Millar, & Kraft, 1994)

“…Although the general steps in the agar extraction process from Gracilaria species are known (Andriamananatonio, Chambat, & Rinaudo, 2007;ArvizuHiguera, Rodríguez-Montesinos, Murillo-Álvarez, Muñoz-Ochoa, & Hernández-Carmona, 2008;Freile-Pelegrin & Murano, 2005;Li et al, 2009;Marinho-Soriano, 2001;Orduña-Rojas et al, 2008;Pereira-Pacheco et al, 2007;Tako, Higa, Medoruma, & Nakasone, 1999), the extraction variables and methodologies differ. Therefore, it is necessary to standardise the extraction process to optimise the agar yield and quality.…”

“…However, the gel properties of many Gracilaria agars can be improved by alkali treatment, which converts L-galactose-6-sulphate to 3,6-anhydro-L-galactose (Duckworth, Hong, & Yaphe, 1971;Freile-Pelegrin & Murano, 2005;Freile-Pelegrin & Robledo, 1997b;Orduña-Rojas et al, 2008), which is responsible for the enhancement of the gel forming ability. Alkali treatment variables like alkali concentration, heating time, temperature are reported to affect the yield and quality of agar from other Gracilaria species (Andriamananatonio et al, 2007;Armisen & Galatas, 1987;Arvizu-Higuera et al, 2008;Li et al, 2009;Orduña-Rojas et al, 2008). Alkali treatment of Gracilaria species must be adapted for each species and variables like temperature and alkali concentration must be adjusted to obtain as much desulphation as possible, while still avoiding the yield losses caused in the treatment (Armisen & Galatas, 1987;Orduña-Rojas et al, 2008).…”

Influência da disponibilidade de nitrato sobre crescimento, atividade da nitrato redutase, composição química e captação de nitrato e fosfato em Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)

“…A análise química do ágar, com relação aos monossacarídeos e grupos substituintes que o compõem, é utilizada para avaliar indiretamente a qualidade do ágar (Matulewicz, 1996). Considera-se que um elevado conteúdo de 3,6-AG caracteriza géis fortes, enquanto alto teor de sulfato está relacionado a géis fracos (Armisen, 1995;Mollet et al, 1998;Meena, 2008;Orduña-Rojas et al, 2008). As algas gracilarióides também incluem espécies utilizadas na alimentação humana e na nutrição de invertebrados cultivados (Critchley, 1993;McHugh, 2003) e que possuem grande potencial como biorremediadoras em cultivos integrados pela sua capacidade de remoção de compostos nitrogenados e fosfatados e de manutenção do teor de oxigênio dissolvido (Hernández et al, 2005(Hernández et al, , 2006.…”

“…tenuifrons, em comparação com outras espécies da família, pois se considera que um menor conteúdo de sulfato esteja relacionado a géis de maior força (Armisen, 1995;Mollet et al, 1998;Meena, 2008;Orduña-Rojas et al, 2008).…”