Abstract
Bifidobacteria are considered one of the most important intestinal probiotics because of their significant health impact. However, this ability is usually limited by gastrointestinal fluid and temperature sensitivity. Emulsification and internal gelation is an encapsulation technique with great potential for probiotic protection during storage and the gastrointestinal transit process. This study prepared microcapsules using an emulsification and internal gelation encapsulation method with sodium alginate, chitosan, and Bifidobacterium longum as wall material, coating material, and experimental strain, respectively. Optical, scanning electron, and focal microscopes were used to observe the microcapsule surface morphology and internal viable cell distribution, and a laser particle size analyzer and zeta potentiometer were used to evaluate the chitosan-coating characteristics. In addition, microcapsule probiotic viability after storage, heat treatment, and simulated gastrointestinal fluid treatment were examined. Alginate microcapsules and chitosan-coated alginate microcapsules both had balling properties and uniform bacterial distribution. The latter kept its balling properties after freeze-drying, verified by scanning electronic microscopy (SEM), and had a clear external coating, observed by an optical microscope. The particle size of chitosan-coated alginate microcapsules was slightly larger than the uncoated microcapsules. The zeta potential of alginate and chitosan-coated alginate microcapsules was negative and positive, respectively. Heat, acid and bile salt tolerance, and stability tests revealed that the decrease of viable cells in the chitosan-coated alginate microcapsule group was significantly lower than that in uncoated microcapsules. These experimental results indicate that the chitosan-coated alginate microcapsules protect B. longum from gastrointestinal fluid and high-temperature conditions.
Highlights
Bifidobacterium longum are an important probiotic bacteria that are able to colonize the human gastrointestinal tract; this species has been added to a variety of dietary supplements, foods, health products, and drugs for regulating intestinal flora, increasing immune function, improving lipid metabolism, and relieving constipation and anti-oxidative action (Jiang et al, 2014; Yeung et al, 2016; Bianchi et al, 2018)
B. longum is a strictly anaerobic gram-positive bacteria that grows between pH 4.5 and 8.5 and is very sensitive to adverse environmental conditions such as oxygen, humidity, temperature, and stomach acid and bile salts (Lievin et al, 2000)
The encapsulation yield of alginate microcapsules and chitosancoated microcapsules reached 95 ± 2.5% and 90 ± 3.4%, respectively. These results indicate that B. longum microcapsule preparation by emulsification and internal gelation and electrostatic adsorption methods efficiently maintained high probiotic activity
Summary
Bifidobacterium longum are an important probiotic bacteria that are able to colonize the human gastrointestinal tract; this species has been added to a variety of dietary supplements, foods, health products, and drugs for regulating intestinal flora, increasing immune function, improving lipid metabolism, and relieving constipation and anti-oxidative action (Jiang et al, 2014; Yeung et al, 2016; Bianchi et al, 2018). B. longum is a strictly anaerobic gram-positive bacteria that grows between pH 4.5 and 8.5 and is very sensitive to adverse environmental conditions such as oxygen, humidity, temperature, and stomach acid and bile salts (Lievin et al, 2000). Finding a preparation method to protect B. longum from adverse environmental effects is necessary to create a stable and effective probiotic supplement. Probiotics can be embedded and isolated from external environments by appropriate microencapsulate preparation for a significantly increased ability to resist acids, bile salts, oxygen, and gastrointestinal conditions (Heidebach et al, 2012). Used wall materials for probiotic microcapsule preparation are sodium alginate and proteins (Cook et al, 2012). Sodium alginate forms a network structure similar to an “egg box” when Na+ on the G unit is exchanged with Ca2+, creating cross-links between alginate molecules (Fareez et al, 2015; Huq et al, 2017)
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