Nutrition & Food Science

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Subject: search.filters.subject.Chitosan

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    Optimization of xanthan chitosan polyelectrolytic hydrogels for microencapsulation of probiotic bacteria
    (2011) Soma, Pavan Kumar; Lo, Martin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The effectiveness of microencapsulation system for targeted delivery of probiotics depends on its ability to protect cells from harsh gastrointestinal conditions of stomach followed by effectively releasing the cells in intestinal conditions. Oppositely charged xanthan and chitosan form stable polyelectrolytic hydrogels capable of encapsulating enzymes and cells. The present study aims at developing an effective microencapsulation system for probiotics by screening and optimizing the factors critical to xanthan-chitosan hydrogel (XCH) capsule formation. The changes in the core pH of the hydrogel capsule in response to simulated gastric juice (SGJ) were characterized. Increase in xanthan concentration and chitosan molecular weight improved the barrier properties, however, increasing complexation time beyond 40 min had the opposite effect. Increase in molecular weight of chitosan resulted in improved viability of probiotic bacteria, Lactobacillus acidophilus, after SGJ treatment, which could be attributed to the differences in hydrogel membrane thickness at the surface of capsule, as evidenced by scanning electron micrographs (SEM). Introducing XCH capsules made with high molecular weight (HMW) chitosan into xanthan solution resulted in the formation of xanthan-chitosan-xanthan hydrogel (XCXH) capsules. Unlike HMW and medium molecular weight (MMW) chitosan, low molecular weight (LMW) chitosan did not form the outer layer beyond XCH, suggesting the significance of chitosan molecular weight in the formation of XCXH. The increased hydrogel thickness of XCXH capsules formed with HMW chitosan compared to XCH capsules rendered better retention of cells in SGJ treatment for a longer period of time, further suggesting the importance of membrane thickness on the hydrogel stability and its barrier properties. Furthermore, complete release of cells from XCXH in simulated intestinal fluid (SIF) was extended by approximately an hour compared to XCH capsules. Smaller, nozzle-sprayed XCXH capsules using HMW chitosan protected probiotic bacteria in SGJ albeit one-log reduction in its protective efficacy compared to syringe extruded capsules. When incorporated into stirred yogurt, XCXH microcapsules improved the viability of L. acidophilus by ~1 log CFU/ml between 15 and 30 days of storage. The stability of bacteria against bile salts was significantly improved, enabling the delivery of prescribed number of cells to attain the claimed health benefits.
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    EFFECT OF CHITOSAN ON THE INDUCTION OF DNA DAMAGE RESPONSE BY SELENIUM COMPOUNDS.
    (2009) Zhang, Shu; Cheng, Wen-Hsing; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Selenium (Se), a nutrient trace mineral, plays important roles in optimizing human health. Chitosan is an effective, natural-oriented material for synthesizing nanopolymers, with preferable properties such as biocompatibility, biodegradation and resistance to certain enzymes. In this study, encapsulated Na2SeO3 and methylseleninic acid (MSeA) with low and medium molecular weight chitosan were used to determine the efficacy of Se in mitigating tumorigenesis. We applied Se compounds, which is from sub-lethal to lethal dose, to colon cancer cell line HCT-116 and normal fibroblasts cell line MRC-5. Analysis of cellular selenium content demonstrated that: 1) Na2SeO3, but not MSeA, treatment resulted in a greater Se retention in HCT-116 than in MRC-5 cells, 2) chitosan encapsulation enhanced Se contents in cells treated with the various Se preparations. Cell survival analysis showed that chitosan encapsulation protected HCT-116 and MRC-5 cells from Na2SeO3 or MSeA induced toxicity. Moreover, this beneficial effect was greater in MRC-5 cells. MSeA encapsulated with chitosan induced phosphorylated ATM Ser-1981 formation in MRC-5 and HCT-116 cells to a less extent as compared to MSeA alone treatment. Taken together, the results suggest that, when encapsulated with chitosan, cells are less susceptible to Se treatment, possibly through a mechanism by which the presence of chitosan attenuates Se-induced activation of ATM and corresponding DNA damage response pathway.