Probiotics and Prebiotics: Concepts, Definitions and History - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 179

A B

O

HOCH 2 H O

H

HOCH 2

H HO H HO

HO

CH 2 OH CH 2 OH

H

O H

OH HO

O

H

CH 2

H HO

CH 2 OH

CH 2 OH

H

OH

O H

H O

n

H

O

H

H CH 2

OH

O H HO

HO

H OH

CH 2 OH

H

OH

Fig. 7.3 Chemical structure of (A) inulin ( n = 2-65) and (B) fructose.

and FOS are non-viscous, soluble fibres obtained from a number of foods, or FOS can be
produced synthetically by adding fructose (Figure 7.3B) units to a sucrose molecule via β-1,2
linkages (Kelly 2009).
IN is present as a storage carbohydrate in a large number of edible grains, fruits and veg-
etables such as wheat, onions, leeks, garlic, asparagus, artichokes and bananas (van Loo et al .
1995; Ritsema and Smeekens 2003). IN-type fructans are widely researched in human and
animal studies with reported beneficial impacts on the Bifidobacterium and Lactobacillus pop-
ulations. IN-type fructans can also be utilized by some Eubacterium and Roseburia strains
which generate high levels of SCFA and an increased molar ratio of butyric acid to total
SCFA compared with other fibres (Pryde et al. 2002; Tremaroli and Bäckhed 2012). Although
IN-type fructans are not natural fibres in fish diets, they may have interesting applications
in aquaculture to stimulate colonization of the 'good' gut bacteria, suppress pathogens and
enhance immune response.
Chemically, oligofructose (OF) and IN can be defined as polydisperse fructans. OF is
always present in IN, a blend of fructose oligomers and polymers, and differs from IN in
regard to its degree of polymerization. It can be produced from IN by controlled partial
enzymatic hydrolysis from chicory roots, for example (Flickinger et al . 2003). Dietary OF
supplementation can have various functional properties such as the improvement of mineral
absorption, impact on bowel habit, interaction with lipid metabolism and preventive effect
against colon cancer (van Loo et al . 1999).
FOS are compounds of vegetable origin and are reported in varying concentrations in
many foods such as onions, asparagus, artichokes, garlic, wheat, bananas, tomatoes and honey
(Roberfroid and Delzenne 1998). Roberfroid et al . (2010) presented a structural characteristic
of FOS and described the degree of polymerization as between 2 and 8. FOS have been
extensively tested in endothermic animals and readers with special interest are referred to the
comprehensive review of Macfarlane et al . (2008).