Chemistry Reference
In-Depth Information
in the GIT are several features that make
Lactobacillus
a potentially better vehicle
for oral vaccination than
S. gordonii
.
Westendorf et al.
167
demonstrated the potential of
E. coli
Nissle 1917 to serve as
a safe carrier for targeted delivery of recombinant proteins to the intestinal mucosa.
The excellent colonization properties of the strain rendered it an ideal carrier for gut-
focused
in situ
synthesis of therapeutic molecules.
Moreover, the successful phase I clinical trial with IL-10-producing
Lactococcus
lactis
for Crohn's disease has opened new avenues for the use of transgenic bacteria
as delivery vehicles. The major advantage of this novel strategy is the avoidance
of systemic side effects associated with conventional therapies. This methodology
opens up an alternative method for local delivery of therapeutic proteins to various
mucosal tissues.
168
18.6 ForMulATIoN oF ProbIoTICs
Probiotics are living organisms in food and dietary supplements that have ben-
eficial health effects beyond their inherent nutritive value. A prerequisite for any
effect of ingested bacteria is successful implantation in the GIT. So, bacteria must
remain viable during gastric transit. Based on the acid stability, it is essential to
consume these microbes with food or to protect them by encapsulation.
169
For par-
ticularly critical applications, microencapsulation technologies have been developed
and successfully applied using various matrices to protect the bacterial cells from
damage caused by the external environment, to improve their survival during gas-
troduodenal transit, and to enhance their stability profile. Microencapsulation is the
process by which small particles or droplets are surrounded by a coating to produce
capsules in micrometer to millimeter range known as microcapsules. The concept of
microencapsulation allows the functional core ingredient (in this case the probiotic
bacterium) to be separated from its environment by a protective coating. Separation
of the functional core ingredient from the environment continues until the release of
the functional ingredient is desired.
170
In a broad sense, encapsulation can be used for many applications, such as sta-
bilizing the core material, controlling the oxidative reaction, providing sustained
or controlled release (both temporal and time-controlled release), masking flavors,
colors, or odors, extending the shelf life, and protecting components against nutri-
tional loss. Polymers, such as alginate, chitosan, carboxymethyl cellulose (CMC),
carrageenan, gelatin, pectin, and so forth, are mainly applied, using various encap-
sulation technologies. Some of techniques and processes used for encapsulating pro-
biotic microrganisms include spray drying, spray-congealing, fluidized bed coating/
air suspension, extrusion-spheronization, coacervation/phase separation technique,
and electrostatic method.
171
However, microencapsulation by spray drying is a well-
established process that can produce large amounts of material. Nevertheless, this
economical and effective technology for protecting materials is rarely considered for
cell immobilization because of the high mortality resulting from simultaneous dehy-
dration and thermal inactivation of microorganisms. Even though the viability of the
