Papel de las actividades superóxido dismutasa y catalasa en la ...

INTRODUCTION
4.3.1. Porphyridium cruentum
Porphyridium cruentum is a red microalga belonging to Rodophyta family and
Porphyridiales order, with spherical cells that lack of cell wall. This alga accumulates
large amounts of fatty acids (9-14% dry weight), specially araquidonic acid (36%) and
noticeable amounts of eicosapentaenoic acid. The protein content ranges from 28 to 39%,
and available carbohydrates vary between 40 and 57%. The biomass contents tocopherol,
vitamin K and a large amount of carotenes (Rebolloso et al., 2000).
P. cruentum cells are capable to excrete a sulphated polysaccharide, an acidic
heteropolymer composed of xylose, glucose, galactose and sulphate esters (You and
Barneu, 2004). This polysaccharide is commercially used as thickener, stabilizer and
emulsifier (Arad et al., 1985, 1988; Adda et al., 1986).
Substances such as araquidonic acid (Koven et al., 2001), carbohydrates (Kumar et
al., 2005), vitamins (Hardie et al., 1990, 1991; Ortuño et al., 1999, 2003; Jeney and Jeney,
2002), carotenoids (Amar et al., 2004) and polysaccharides (Siwicki et al., 1994;
Santarém et al., 1997; Castro et al., 1999; Bagni et al., 2000, 2005; Esteban et al., 2001;
Jeney and Jeney, 2002; Cook et al., 2003; Couso et al., 2003) present in different
organisms, have been demonstrated their immunostimulant effects on fish. All of these
compounds have been determined in P. cruentum.
In addition, the fact that P. cruentum culture is not costly makes this alga a good
candidate as a source of immunostimulant active substances. However, the
polysaccharide extraction is a laborious process; moreover intraperitoneal
administration is not advisable due to stress by handling. For this reason it is convenient
to simplify the immunostimulant administration, providing whole and oral,
supplementing feed. Last years the number of works, that study whole organisms is
increasing, such as yeasts (Siwicki et al., 1994; Ortuño et al., 2002; Rodríguez et al.,
2003), fungus (Rodríguez et al., 2004) and probiotics (Verschuere et al., 2000; Irianto and
Austin, 2003; Salinas et al., 2005; Díaz-Rosales et al., 2006). However, in spite of the
large number of studies carried out with extracts or compounds derived from algae
(Koven et al., 2001; Castro et al., 2004; Skjermo and Bergh, 2004; Díaz-Rosales et al.,
83