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35 Biochemistry and Probiotics 681et al. 2006). It is unknown if cells that are suddenly exposed
to bile salts upon entrance to the duodenum can increase their
BSH level and increase their functionality. Thus, BSH activity in
the GI tract can potentially be enhanced by culture preparation
methodologies prior to consumption.
It must be kept in mind, however, that the production of sec-
ondary deconjugated bile salts through BSH activity may have
undesirable effects. Contradictory data suggest that colon can-
cer could be enhanced (Patel et al. 2010), while another study
suggests thatLactobacillus reutericould have protective prop-
erties through precipitation of the deconjugated bile salts and
a physical binding of bile salts by the bacterium, thereby mak-
ing the harmful bile salts less bioavailable (De Boever et al.
2000). Therefore, more data are needed to better ascertain the
desirability of BSH activity.Gas DiscomfortsIt is considered that oligosaccharides that are not broken down
by the human GI enzymes may be responsible for gas production
in the GI tract (Yamaguishi et al. 2009). Since they are not as-
similated in the small intestine, these oligosaccharides end up in
the colon where they are fermented by the microbiota (LeBlanc
et al. 2008). Unfortunately, the consumption of beans has been
associated with gas production in the GI tract (Machaiah et al.
1999) if consumed in sufficient amount. Fortunately, symptoms
reduce on frequent and continuous consumption (O’Donnell and
Fleming 1984), but means to reduce discomforts are nevertheless
desirable.
Legumes can be good substrates for the growth of probiotics
(Chopra and Prasad 1990), but strain selection is required (Farn-
worth et al. 2007). Although some probiotic cultures only use
the short-chain carbohydrates in legumes (Desai et al. 2002), the
prospect of introducing probiotics into a high-fiber bean product
is a very promising one. It is unknown at the present time, if
the carbohydrates in beans can indeed have a positive impact on
survival and growth in the GI tract. In addition to the health bene-
fits, probiotics may also have the potential of reducing problems
associated with digestibility.
Various studies in animals (LeBlanc et al. 2008) and in humans
(Nobaek et al. 2000, Di Stefano et al. 2004) have shown the po-
tential of probiotics to reduce the symptoms of gas discomforts.
There appears to be a link between the synthesis ofα-gal, which
hydrolyze the oligosaccharides in beans, and the bioactivity of
the cultures (LeBlanc et al. 2008). As a result, a product (Proviva
Fruit Drink) has received an opinion by the Swedish Nutrition
Foundation (SNF 2003) “that an effect to decrease flatulence
is reasonably well documented.” This was apparently the first
such specific health benefit recognition for probiotic bacteria.
The culture used wasLactobacillus plantarum299v. However,
a similar petition withL. rhamnosusGG was not granted (EFSA
2008).
This benefit of probiotics on sugar metabolism in the GI tract
throughα-gal resembles that ofβ-gal for lactose maldigestion
mentioned previously. It is unknown to what extent live cells are
required for the health benefit to occur.Other BenefitsFor probiotic bacteria, the main purpose of proteases is for nu-
trition. By hydrolysing proteins in the medium, the cells gain
access to peptides and amino acids for the synthesis of their own
proteins. However, there are instances where peptides show bi-
ological activities. Milk caseins have particularly been assessed
in this respect (Korhonen and Pihlanto 2006). Thus, milk pro-
teins contain peptidic angiotensin I-converting enzyme (ACE)
inhibitors, which can be released by proteolysis during milk fer-
mentation by some strains ofL. helveticus(Leclerc et al. 2002).
Hydrolysis of soy proteins by probiotic lactobacilli has also re-
vealed the presence of ACE inhibitors (Donkor et al. 2005).
Through the ACE inhibition, peptides exert antihypertensive ac-
tivity. It is important to stress that the functionality of probiotics
is linked to the substrate on which growth has occurred. That
is why the concept of probioactive not only includes bioac-
tive compounds synthesized by the probiotic cells as such, such
as exopolysaccharides, but also includes probioactives that are
specifically the result of transformation of the food substrate.
This link between probiotic functionality and the food matrix
may partially explain why there are contradictory data on the
benefits of probiotics in the literature. An ACE inhibition activ-
ity recorded in fermented milk may unfortunately not extend to
fermented fruits or vegetables low in proteins.
The production of peptides is not the only way lactic cultures
can affect blood pressure. Certain strains ofLactococcus lactis
convert glutamic acid to gamma-amino butyric acid (GABA)
thanks to glutamate decarboxylase (Inoue et al. 2003, Minervini
et al. 2009). High levels of free glutamate are rarely found in
foods, and proteolysis is generally required to release gluta-
mate from proteins before GABA production can occur. The
activity of glutamate decarboxylase tends to be higher in acid
environments (Komatsuzaki et al. 2005). Therefore, fermented
milk or soy beverages seem particularly well suited for GABA
production.
Foods naturally contain antioxidants and bioactive com-
pounds, but some are linked to sugars or proteins. When
combined with sugars or other food ingredients, some of these
bioactive compounds have less biological activity. Therefore,
deconjugation of the bioactives and their release into the prod-
uct are desirable. Two examples serve to illustrate this particular
concept: (1) isoflavones in soy and (2) quercetin in onions.
Antioxidants are bioactive compounds that are quite varied in
chemical. In foods, examples include carotenoids, terpenes, an-
thocyanins, isoflavones, and flavonoids like quercetin. Quercetin
is of interest because of its high antioxidant capacity, that is,
229% higher than that of ascorbic acid (Kim and Lee 2004). In
onions, quercetin is mainly found in three forms: (1) quercetin
diglucoside (Qdg), (2) quercetin monoglucoside (Qmg), and (3)
free quercetin. Fermentation of red onions by lactic cultures sub-
stantially increased the proportion of Qmg (Bisakowski et al.
2007), that may have a positive effect as fractions containing
higher ratios of Qmg:Qdg have been reported to have higher
antioxidant activity (Makris and Rossiter 2001). The enzymes
responsible for this useful bioconversion in onions are glucosi-
dases. These enzymes contribute to enhancing the biological