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Microencapsulation of Actives in Cross-linked Alginates Prepared by Spray-Drying.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Microencapsulation of Actives in Cross-linked Alginates Prepared by Spray-Drying./
作者:	Strobel, Scott Alan.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
面頁冊數:	205 p.
附註:	Source: Dissertations Abstracts International, Volume: 79-11, Section: B.
Contained By:	Dissertations Abstracts International79-11B.
標題:	Bioengineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10688390
ISBN:	9780355969375

Microencapsulation of Actives in Cross-linked Alginates Prepared by Spray-Drying.
Strobel, Scott Alan.

Microencapsulation of Actives in Cross-linked Alginates Prepared by Spray-Drying. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 205 p.

Source: Dissertations Abstracts International, Volume: 79-11, Section: B.

Thesis (Ph.D.)--University of California, Davis, 2018.

This item is not available from ProQuest Dissertations & Theses.

In the process of microencapsulation, a wall material envelops a cargo material to form microscopic capsules and typically provides additional functionality, such as protecting the cargo or controlling its release. A promising wall material for microencapsulation, sodium alginate forms electrostatic cross-links in the presence of multivalent cations such as calcium, spontaneously forming a dense gel matrix. However, typical methods for preparing cross-linked alginate microbeads are very challenging to scale industrially. The UC Davis spray-drying technology for producing cross-linked alginate microcapsules (CLAMs) combines particle formation, alginate matrix cross-linking, and dehydration steps into a single scalable unit operation. Cross-linking is achieved in situ during spray-drying by controlling the chemistry of the inlet formulation. During spray-drying, the vaporization of a base acidifies the atomized droplets, dissolving a calcium salt to avail calcium ions for cross-linking the alginate. Prior to commercial implementation, this scalable technology must demonstrate utility for producing CLAMs that exhibit desirable functional characteristics for a variety of applications. In this work, I hypothesized that adjusting the formulation parameters (e.g. calcium content, emulsifier choice, and additive content) will modulate the physicochemical structure of CLAMs, including cross-linking, to influence their functional attributes for end-use applications. Three fundamentally unique cargo were microencapsulated to demonstrate applicability in pharmaceutical, food, and agricultural systems. Prior to assessing how formulation parameters influence cross-linking, a method was developed to determine the extent of cross-linking by assessing the quantity of alginate that could dissociate from the matrix in water. The impact of calcium content on CLAM physiochemical structure was investigated. Alginate cross-linking increased with rising calcium content in the formulation. For a low-viscosity alginate, upon increasing the calcium content beyond 0.2%, the soluble fraction of the alginate matrix remained constant at approximately 25%. CLAMs adopted a more spherical morphology as calcium content increased, which may be related to the detection of residual calcium phosphate in CLAMs prepared with calcium content of 0.25% or greater. However, cross-linking did not influence particle size. The initial release of fluorescent dextran was slightly delayed from highly cross-linked CLAMs, which may be related to the slower and less extensive alginate leaching. The dextran served as a model cargo simulating a hydrophilic macromolecule drug or bioactive compound. The baseline properties of oil-loaded CLAMs were thoroughly characterized before investigating how formulation variables influence the structure and function of CLAMs intended for food systems. CLAMs were prepared with emulsified oil droplets on the order of 200 to 300 nm, the size of which remained unchanged after spray-drying. Electron and fluorescence microscopy revealed that oil cargo was uniformly distributed throughout the CLAMs. Particle size of CLAMs, which was generally on the order of 2-20 µm in diameter, increased with oil cargo loading. CLAMs with 25% oil loading released approximately 20% of cargo in simulated gastric fluid and over 90% in simulated intestinal fluid after 2 h incubation, suggesting that CLAMs are a promising system for enteric delivery of lipophilic bioactives incorporated into functional foods. Subsequently, I investigated how calcium content and emulsifier choice in the CLAMs formulation affect the stability of lipophilic bioactive cargo, specifically the omega-3 polyunsaturated fats EPA and DHA found in fish oil. Neither the extent of cross-linking nor the emulsifier choice (Tween 80 or whey protein isolate (WPI)) influenced the duration of EPA and DHA stability. However, the initial retention of EPA and DHA (but not oil) was significantly greater in CLAMs prepared with WPI, which also featured higher powder yields. Incorporating modified starch into the high cross-linking formulation reduced surface oil content and prolonged shelf life, with stability duration increasing with modified starch content. Even with substantial modified starch content, CLAMs exhibited enteric release behavior. This work suggests that CLAMs show promise for stabilizing lipophilic bioactives in functional foods and providing a mechanism of delivery to the site of absorption in the human gastrointestinal system. Finally, the survival of plant-beneficial bacteria was investigated in the context of tuning the calcium content of CLAMs. The spray-drying microencapsulation process did not significantly reduce the viable population of bacteria, which exceeded 1010 CFU/g powder initially. Over one year of storage, the bacterial population declined by 4 to 5 log CFU/g. The amplified cross-linking induced by increased calcium content did not significantly impact cell viability, storage survival, or dry particle size. However, enhancing the alginate cross-linking appeared to limit the release of bacteria from CLAMs suspended in water. This capacity to tune bacterial release may prove to be a highly useful functional attribute for on-seed or foliar spray applications of microencapsulated bacteria to crops. (Abstract shortened by ProQuest.).

ISBN: 9780355969375Subjects--Topical Terms:

657580
Bioengineering.
Subjects--Index Terms:

Alginate

Microencapsulation of Actives in Cross-linked Alginates Prepared by Spray-Drying.
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500 $a Publisher info.: Dissertation/Thesis.
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502 $a Thesis (Ph.D.)--University of California, Davis, 2018.
506 $a This item is not available from ProQuest Dissertations & Theses.
506 $a This item must not be sold to any third party vendors.
520 $a In the process of microencapsulation, a wall material envelops a cargo material to form microscopic capsules and typically provides additional functionality, such as protecting the cargo or controlling its release. A promising wall material for microencapsulation, sodium alginate forms electrostatic cross-links in the presence of multivalent cations such as calcium, spontaneously forming a dense gel matrix. However, typical methods for preparing cross-linked alginate microbeads are very challenging to scale industrially. The UC Davis spray-drying technology for producing cross-linked alginate microcapsules (CLAMs) combines particle formation, alginate matrix cross-linking, and dehydration steps into a single scalable unit operation. Cross-linking is achieved in situ during spray-drying by controlling the chemistry of the inlet formulation. During spray-drying, the vaporization of a base acidifies the atomized droplets, dissolving a calcium salt to avail calcium ions for cross-linking the alginate. Prior to commercial implementation, this scalable technology must demonstrate utility for producing CLAMs that exhibit desirable functional characteristics for a variety of applications. In this work, I hypothesized that adjusting the formulation parameters (e.g. calcium content, emulsifier choice, and additive content) will modulate the physicochemical structure of CLAMs, including cross-linking, to influence their functional attributes for end-use applications. Three fundamentally unique cargo were microencapsulated to demonstrate applicability in pharmaceutical, food, and agricultural systems. Prior to assessing how formulation parameters influence cross-linking, a method was developed to determine the extent of cross-linking by assessing the quantity of alginate that could dissociate from the matrix in water. The impact of calcium content on CLAM physiochemical structure was investigated. Alginate cross-linking increased with rising calcium content in the formulation. For a low-viscosity alginate, upon increasing the calcium content beyond 0.2%, the soluble fraction of the alginate matrix remained constant at approximately 25%. CLAMs adopted a more spherical morphology as calcium content increased, which may be related to the detection of residual calcium phosphate in CLAMs prepared with calcium content of 0.25% or greater. However, cross-linking did not influence particle size. The initial release of fluorescent dextran was slightly delayed from highly cross-linked CLAMs, which may be related to the slower and less extensive alginate leaching. The dextran served as a model cargo simulating a hydrophilic macromolecule drug or bioactive compound. The baseline properties of oil-loaded CLAMs were thoroughly characterized before investigating how formulation variables influence the structure and function of CLAMs intended for food systems. CLAMs were prepared with emulsified oil droplets on the order of 200 to 300 nm, the size of which remained unchanged after spray-drying. Electron and fluorescence microscopy revealed that oil cargo was uniformly distributed throughout the CLAMs. Particle size of CLAMs, which was generally on the order of 2-20 µm in diameter, increased with oil cargo loading. CLAMs with 25% oil loading released approximately 20% of cargo in simulated gastric fluid and over 90% in simulated intestinal fluid after 2 h incubation, suggesting that CLAMs are a promising system for enteric delivery of lipophilic bioactives incorporated into functional foods. Subsequently, I investigated how calcium content and emulsifier choice in the CLAMs formulation affect the stability of lipophilic bioactive cargo, specifically the omega-3 polyunsaturated fats EPA and DHA found in fish oil. Neither the extent of cross-linking nor the emulsifier choice (Tween 80 or whey protein isolate (WPI)) influenced the duration of EPA and DHA stability. However, the initial retention of EPA and DHA (but not oil) was significantly greater in CLAMs prepared with WPI, which also featured higher powder yields. Incorporating modified starch into the high cross-linking formulation reduced surface oil content and prolonged shelf life, with stability duration increasing with modified starch content. Even with substantial modified starch content, CLAMs exhibited enteric release behavior. This work suggests that CLAMs show promise for stabilizing lipophilic bioactives in functional foods and providing a mechanism of delivery to the site of absorption in the human gastrointestinal system. Finally, the survival of plant-beneficial bacteria was investigated in the context of tuning the calcium content of CLAMs. The spray-drying microencapsulation process did not significantly reduce the viable population of bacteria, which exceeded 1010 CFU/g powder initially. Over one year of storage, the bacterial population declined by 4 to 5 log CFU/g. The amplified cross-linking induced by increased calcium content did not significantly impact cell viability, storage survival, or dry particle size. However, enhancing the alginate cross-linking appeared to limit the release of bacteria from CLAMs suspended in water. This capacity to tune bacterial release may prove to be a highly useful functional attribute for on-seed or foliar spray applications of microencapsulated bacteria to crops. (Abstract shortened by ProQuest.).
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653 $a Omega-3 fatty acids
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