CHAPTER 7
Polysaccharide Production by Microalgae from the Adriatic Sea
L. Boni, M. Cangini, A. Grifoni, F. Guerrini, and R. Pistocchi
ABSTRACT
Polysaccharide production by different phytoplankton organisms from the Adriatic Sea was
measured under optimal and stress conditions. The highest sugar amount was produced and
released by diatoms and, in all the algae tested, total and extracellular polysaccharide content
increased during growth. The amount of extracellular polysaccharides was found to increase
under different stress conditions such as a high NIP ratio, presence of bacteria associated with P
limitation, presence of metals.
Introduction
A well known aspect of phytoplankton physiology is represented by the release of organic compounds which usually consist of photosynthetic
products that are temporarily in excess and are
discarded rather than accumulated as reserve
material (Fogg 1983). In diatoms the production
of extracellular polymeric substances represents
a relevant and physiological aspect of their
growth. Polysaccharides are the primary component of these substances and are known to have
several functions such as to promote motility,
permit sessile adhesion or colony formation,
avoid dessiccation, stabilize sediments, favour
association with bacteria, protect against physical or chemical changes of the environment and
others (Hoagland et al. 1993). Polysaccharide
production and release is known to increase
under some stress conditions such as the presence of a high NIP ratio (Myklestad 1977). We
applied this and other environmental stresses in
the attempt to understand when polysaccharide
extrusion was enhanced and, in particular, we
studied this aspect in micro algae isolated from
the Northern Adriatic Sea, an area periodically
affected by mucilages.
Material and Methods
The algae were cultured in fJ2 medium (Guillard
and Ryther 1962), with an unchanged or decreased
phosphorus content; sugars were measured
according to Dubois et al. (1956) and the work
scheme ofPistocchi et al. (1997).
Results
Polysaccharide Production
Polysaccharide production was measured
in the dinoflagellates Gonyaulax polyedra
(Gon), Gymnodinium sp. (Gymn), Prorocentrum
micans (Pror), and in the diatoms Thalassiosira
sp. (Thal), Asterionellopsis glacialis (Ast),
Achnanthes brevipes (Ach), Cylindrotheca
closterium (C. clost), Cylindrotheca fusiformis (c.
fus), during different periods of growth (days 7,
12, 16,21). Both total and extracellular polysaccharides accumulated mostly in the stationary
phase of growth and the highest amount
(expressed as llglml culture) was produced
and released extracellularly by the algae belonging to the diatom group. In particular, the species
Universita di Bologna, Scienze Ambientali, Via Tombesi daU'Ova 55,48100 Ravenna, Italy
F.M. Faranda, L. Guglielmo, G. Sperle (eds)
Mediterranean Ecosystems; Structures and Processes
@ Springer-Verlag ltalia 2001
Polysaccharide Production by Microalgae from the Adriatic Sea
L. Boni, M. Cangini, A. Grifoni, F. Guerrini, and R. Pistocchi
ABSTRACT
Polysaccharide production by different phytoplankton organisms from the Adriatic Sea was
measured under optimal and stress conditions. The highest sugar amount was produced and
released by diatoms and, in all the algae tested, total and extracellular polysaccharide content
increased during growth. The amount of extracellular polysaccharides was found to increase
under different stress conditions such as a high NIP ratio, presence of bacteria associated with P
limitation, presence of metals.
Introduction
A well known aspect of phytoplankton physiology is represented by the release of organic compounds which usually consist of photosynthetic
products that are temporarily in excess and are
discarded rather than accumulated as reserve
material (Fogg 1983). In diatoms the production
of extracellular polymeric substances represents
a relevant and physiological aspect of their
growth. Polysaccharides are the primary component of these substances and are known to have
several functions such as to promote motility,
permit sessile adhesion or colony formation,
avoid dessiccation, stabilize sediments, favour
association with bacteria, protect against physical or chemical changes of the environment and
others (Hoagland et al. 1993). Polysaccharide
production and release is known to increase
under some stress conditions such as the presence of a high NIP ratio (Myklestad 1977). We
applied this and other environmental stresses in
the attempt to understand when polysaccharide
extrusion was enhanced and, in particular, we
studied this aspect in micro algae isolated from
the Northern Adriatic Sea, an area periodically
affected by mucilages.
Material and Methods
The algae were cultured in fJ2 medium (Guillard
and Ryther 1962), with an unchanged or decreased
phosphorus content; sugars were measured
according to Dubois et al. (1956) and the work
scheme ofPistocchi et al. (1997).
Results
Polysaccharide Production
Polysaccharide production was measured
in the dinoflagellates Gonyaulax polyedra
(Gon), Gymnodinium sp. (Gymn), Prorocentrum
micans (Pror), and in the diatoms Thalassiosira
sp. (Thal), Asterionellopsis glacialis (Ast),
Achnanthes brevipes (Ach), Cylindrotheca
closterium (C. clost), Cylindrotheca fusiformis (c.
fus), during different periods of growth (days 7,
12, 16,21). Both total and extracellular polysaccharides accumulated mostly in the stationary
phase of growth and the highest amount
(expressed as llglml culture) was produced
and released extracellularly by the algae belonging to the diatom group. In particular, the species
Universita di Bologna, Scienze Ambientali, Via Tombesi daU'Ova 55,48100 Ravenna, Italy
F.M. Faranda, L. Guglielmo, G. Sperle (eds)
Mediterranean Ecosystems; Structures and Processes
@ Springer-Verlag ltalia 2001