Biology Reference
In-Depth Information
Prebiotics
This term was introduced to defi ne “a non-digestible food ingredient that
benefi cially affects the host by selectively stimulating the growth and/
or activity of one or a limited number of bacteria in the colon” (Gibson
and Roberfroid, 1995) and later redefi ned as “a selectively fermented
ingredient that allows specifi c changes, both in the composition and/
or activity in the gastrointestinal microfl ora that confers benefi ts upon
the well-being and health” (Robertfroid, 2007). A question could be if
microorganisms, at a certain point, could also be considered as prebiotics?
Not according to the defi nition provided because at some point, the host
could digest the microorganisms, and that they are also not fermented
ingredients. It is more suitable for feed ingredients that specifi cally
enhance the activity of certain microorganisms, such as non-digestible
carbohydrates (starch), some peptides, proteins, and lipids (Gibson and
Roberfroid, 1995). In synthesis, a probiotic is a live microorganism and a
prebiotic is an ingredient, and both confer benefi ts upon the well-being
and health of the host.
Selection of Probiotics
Sources
Sources of potential probiotic strains have been either microbial culture
collections, or from the environment of the cultured organism (Gram and
Hjelm, 2002; Maeda et al., 1997). From the environment, common sources
are successful rearing cycles (Planas
et
al., 2006), culture water (Abidi,
2003; Balcazar and Rojas-Luna, 2007; Li et al., 2006), and uncontaminated
seawater (Abidi, 2003; Garriques and Arevalo, 1995; Gomez-Gil et al.,
2002). Sometimes, they have also been isolated from the gut of healthy
organisms, especially in the case of fi shes (Ringo et al., 2007; Spanggaard
et al., 2001), or from other organs, such as the hepatopancreas of wild
shrimps (Gullian
et al
.
, 2004). The theory behind selecting these sources
is that bacteria colonizing these habitats under these circumstances are
less likely to be pathogenic. That, of course, does not guarantee that they
are capable of becoming a good probiont. It might be advisable to look
for potential probiotic bacteria right in the “battlefi eld”, that is, where
they are constantly tested for fi tness and survival against their “natural
enemies”, harmful bacteria that might be more capable of colonizing a
certain host. These “battlefi elds” could be infected organisms, polluted
culture water, etc. Strains coming from these “dangerous” sources should
be tested for their pathogenicity. It is very rare that in a diseased aquatic
organism, especially in invertebrates, only pathogenic bacteria are found.
Most often, these pathogens dominate, more so in the latter stages of the
infection, but other bacteria are also to be found and these could be the
ones of interest.
