BLBS102-c35 BLBS102-Simpson March 21, 2012 14:9 Trim: 276mm X 219mm Printer Name: Yet to Come
680 Part 6: Health/Functional Foodsstrong (R^2 =0.49) (Champagne and Gardner 2008). More data
are needed for the enzymatic activities associated with resistance
to long-term exposure to acid foods.BIOCHEMISTRY AND HEALTH
FUNCTIONALITYSurvival to Gastric AcidityMany bacteria do not survive passage to the conditions of the
GI tract and, as mentioned previously, one of the most important
criteria for functionality of probiotic bacteria is the survival to
acid conditions of the stomach (Prasad et al. 1998, Mainville
et al. 2005).
Proton-translocating ATPases are the enzymes that are prin-
cipally involved in maintaining a high pHi, as they contribute
to excrete protons outside the cell (De Angelis and Gobbetti
2004). There are other enzymatic systems as well. The arginine
deiminase pathway, which involves three enzymes, contributes
to maintaining pHiby producing ammonia as well as ATP for
the ATPases (De Angelis and Gobbetti 2004). It must be kept
in mind that there must be a source of ATP for the proton-
translocating enzymes to function. Therefore, acid resistance of
probiotic cells in the stomach can also be linked to the presence
of a fermentable sugar in the medium (Corcoran et al. 2005).
This shows that numerous enzymatic systems interact to prevent
a big drop in pHi, when the bacteria produce lactic acid during
their fermentation or when the cells are exposed to an exocellular
environment having a low pH.
As mentioned previously, cells can be adapted to enhance
their resistance to acid. This ATR has been shown to be effective
on subsequent short-term acid stresses such as those that occur
when cells are exposed to gastric solutions. As a result, enzy-
matic adaptations (H+-ATPases or others) improve the survival
of probiotics to passage in the GI tract (Matto et al. 2006).
In summary, it can be assumed that survival of probiotics to
passage in the stomach requires at least two sets of enzymes:
(1) those that can assimilate sugar or amino acid substrates and
generate ATP and (2) those that excrete protons outside the cell
to help maintain an acceptable pHi.Lactose MaldigestionLactase insufficiency indicates that the concentration of theβ-
gal in the cells of the small intestine mucosa is very low. As
a result, hypolactasia causes insufficient digestion of lactose in
the GI tract. This phenomenon is alternatively called lactose
malabsorption, lactose maldigestion, or lactose intolerance by
various authors. In addition to the intrinsic intestinal lactase
activity and its determinants, other parameters that affect lac-
tose digestion include ethnic origin and age. Lactase activity is
high at birth, decreases in childhood and adolescence, and re-
mains low in adulthood. The symptoms of lactose intolerance
are increased breath hydrogen, flatulence, abdominal pain, and
diarrhoea.
An official recognition of the benefit of yogurt in lactose
digestion in the GI tract has been granted (EFSA 2010) andevidence points toward a reduction of symptoms of intolerance
in lactose maldigesters. The synthesis ofβ-gal by the yogurt
starter culture is considered as the probioactive component in-
volved in the positive effects on intestinal functions and colonic
microflora, and reduced sensitivity to symptoms. Unbroken bac-
terial cell walls act as a mechanical protection of lactase during
gastric transit and also affect the discharge of the enzyme into
the small intestine; they consequently influence the efficiency
of the system. It must also be mentioned that reduced amounts
of lactose are often found in cheeses due to lactose utilization
by starter microorganisms (Kilara and Shahani 1975, De Vrese
et al. 2001).
Lactose catabolism mainly occurs byβ-gal derived from the
yogurt starters in fermented milk processing. The optimum ac-
tivity of streptococcalβ-gal is at a neutral pH and at 55◦Cin
presence of buffer. Activity ofβ-gal is stimulated in presence of
Mg^2 +and oxgall (0.15 mL/100mL), while ethylenediaminete-
traacetic acid (EDTA) causes inhibition. Thermal denaturation
occurs at 60◦C, although stability can be enhanced by the ad-
dition of bovine serum albumin (Chang and Mahoney 1994).
Therefore, it can be expected that yogurt drinks heated at high
temperatures to enable storage at room temperature would not
contain activeβ-gal and therefore not present the enzymatic
functionality.
In comparison with yogurt cultures, other probiotic bacteria
usually promote lactose digestion in the small intestine less
efficiently. However, it is suggested that some probiotic bacteria
may act by preventing symptoms of intolerance in the large
intestine in addition to (or rather than) by improving lactose
digestion in the small intestine (De Vrese et al. 2001). It is
noteworthy that yogurt cultures are generally not included in
lists of probiotic bacteria (Stanton et al. 2003, CFIA 2009),
presumably because they generally do highly survive the gastric
transit nor grow in the intestines, but some authors do consider
them as candidates (Santosa et al. 2008).Blood Cholesterol LevelHigh cholesterol in serum is associated with the incidence of
human cardiovascular diseases (Othman et al. 2011). One of the
health-promoting benefits of probiotics is their ability to reduce
blood cholesterol, which was observed in humans (Xiao et al.
2003) and animals (Du Toit et al. 1998, Nguyen et al. 2007).
However, some studies have been negative (Simons et al. 2006).
This points to a specific biological activity that is variable be-
tween cultures. Bile salt hydrolase (BSH) in probiotics renders
them more tolerant to bile salts, and it is believed that this ac-
tivity also helps to reduce the blood cholesterol level of the host
(Taranto et al. 1997). Indeed, oral administration of encapsu-
lated BSH reduced serum cholesterol levels in mice by 58%
(Sridevi et al. 2009). It is thought that bile salt deconjugation
affects its enterohepatic circulation (Kim and Lee 2008), but the
BSH hypothesis has not yet been completely demonstrated or
elucidated.
Three different types of BSH from variousBifidobacterium
strains have been identified (Kim et al. 2004, Kim and Lee 2008).
Data show that higher BSH activity can be acquired (Noriega