influencing animal health, especially in connection with intensive breeding conditions and the recent trend to avoid ‘‘chemicals,’’ like antibiotics. Today, there is
evidence that very small amounts of microalgal biomass, almost exclusively of the
genera Chlorella, Scenedesmus, and Spirulina, can positively affect the physiology
of animals. In particular, a nonspecific immune response and a boosting of the
immune system of the animals was observed (Richmond 2004). Microalgae or its
products have recently been used as probiotics in the aquaculture industry in order
to increase production. The research on probiotics for aquatic animals is increasing
with the demand for environment friendly aquaculture. A wide range of microalgae have been evaluated, although the mode of action of the probiotics is rarely
investigated, but possibilities include competitive exclusion, i.e., the probiotics
actively inhibit the colonization of potential pathogens in the digestive tract by
antibiosis or by competition for nutrients or space, alteration of microbial
metabolism, and by the stimulation of host immunity. Probiotics may stimulate
appetite and improve nutrition by the production of vitamins, detoxification of
compounds in the diet, and by the breakdown of indigestible components. On the
other hand, microalgae could be necessary to improve quality or growth characteristics in aquaculture. For example, copepods are recognized as excellent feeds
for fish larvae, but they have proven difficult to produce in intensive systems due to
the lack of feed (microalgae), so it is necessary to know the biology of microalgae
species, which could improve their production rates and support fish production in
a friendly manner.
8.3 Microalgae Selection
For the successful set up of a microalgal culture, it is necessary to select appropriate strains taking into account goals and available resources. First of all it is
necessary to keep in mind for what purpose the production will be used; microalgae have been used for food, feed, biofuels, vitamins, pigments, or a combination
of these. Different species contain different amounts of the various possible
products. Another important factor for selection is growth rate of the microalgae
under the circumstances available in order to get sufficient production. The following considerations need to be taken into account:
Diurnal temperature fluctuations Working with large-scale microalgae cultures
requires care with temperature fluctuations. Temperature fluctuation can decrease
culture production efficiency, or may increase production depending on the species
(Renaud et al. 2002). In order to solve this undesirable situation on growth culture,
there are two options; first consider strains that are adapted to wide temperature
fluctuations (Vonshak 1987; Becker 1994; Abalde et al. 1995). The second option
is temperature control to prevent large fluctuations.
Photoinhibition Light is a necessary factor for microalgae, however, it can also
be a limiting factor. Often, the upper layers in a microalgae culture are exposed to
a high irradiance so that cell photo-oxidation can occur resulting in a state of
8 Microalgae and Cyanobacteria Production for Feed and Food Supplements
263
evidence that very small amounts of microalgal biomass, almost exclusively of the
genera Chlorella, Scenedesmus, and Spirulina, can positively affect the physiology
of animals. In particular, a nonspecific immune response and a boosting of the
immune system of the animals was observed (Richmond 2004). Microalgae or its
products have recently been used as probiotics in the aquaculture industry in order
to increase production. The research on probiotics for aquatic animals is increasing
with the demand for environment friendly aquaculture. A wide range of microalgae have been evaluated, although the mode of action of the probiotics is rarely
investigated, but possibilities include competitive exclusion, i.e., the probiotics
actively inhibit the colonization of potential pathogens in the digestive tract by
antibiosis or by competition for nutrients or space, alteration of microbial
metabolism, and by the stimulation of host immunity. Probiotics may stimulate
appetite and improve nutrition by the production of vitamins, detoxification of
compounds in the diet, and by the breakdown of indigestible components. On the
other hand, microalgae could be necessary to improve quality or growth characteristics in aquaculture. For example, copepods are recognized as excellent feeds
for fish larvae, but they have proven difficult to produce in intensive systems due to
the lack of feed (microalgae), so it is necessary to know the biology of microalgae
species, which could improve their production rates and support fish production in
a friendly manner.
8.3 Microalgae Selection
For the successful set up of a microalgal culture, it is necessary to select appropriate strains taking into account goals and available resources. First of all it is
necessary to keep in mind for what purpose the production will be used; microalgae have been used for food, feed, biofuels, vitamins, pigments, or a combination
of these. Different species contain different amounts of the various possible
products. Another important factor for selection is growth rate of the microalgae
under the circumstances available in order to get sufficient production. The following considerations need to be taken into account:
Diurnal temperature fluctuations Working with large-scale microalgae cultures
requires care with temperature fluctuations. Temperature fluctuation can decrease
culture production efficiency, or may increase production depending on the species
(Renaud et al. 2002). In order to solve this undesirable situation on growth culture,
there are two options; first consider strains that are adapted to wide temperature
fluctuations (Vonshak 1987; Becker 1994; Abalde et al. 1995). The second option
is temperature control to prevent large fluctuations.
Photoinhibition Light is a necessary factor for microalgae, however, it can also
be a limiting factor. Often, the upper layers in a microalgae culture are exposed to
a high irradiance so that cell photo-oxidation can occur resulting in a state of
8 Microalgae and Cyanobacteria Production for Feed and Food Supplements
263