A new method for encapsulating low-molecular weight, water-soluble substances
in lipid-walled microcapsules (LWMs) for delivery to marine bivalves was developed,
characterized, and tested. LWMs produced by a spray technique (spray microcapsules,
SMs) were demonstrated to encapsulate both aqueous (polymeric dye or oxytetracycline
hydrochloride) and particulate (riboflavin) core materials within a capsule wall composed
of triacylglycerides. Core materials were most effectively delivered in a capsule wall
composed of tripalmitin. Addition of lower melting point lipids to soften the capsule wall
significantly reduced (up to a nine-fold reduction) delivery of aqueous core materials, but
did not significantly affect particulate riboflavin delivery.
The composition of the capsule wall was demonstrated to affect the digestibility of
LWMs. Addition of 40% w/w fish oil to the tripalmitin wall was required for Manila
clam spat (Tapes philippinarum) enzymatically digest LWMs (convert triaclyglycerides to
free fatty acids). Delivery of aqueous and particulate core materials by microcapsules was
assessed by feeding clams LWMs containing an aqueous core of polymeric dye or a
particulate core of oxytetracycline hemicalcium salt (OTC.HEM). The physical
appearance and absence of core material in capsules observed in clam fecal strands
suggested release and delivery of core materials in the clam's digestive system.
Optimal methods for encapsulating and storing oxytetracycline were assessed.
Oxytetracycline hydrochloride was most efficiently encapsulated (3.2 mg core/ 100 mg
lipid) and retained (30%) as an aqueous core in LWMs produced by a double-emulsion
process (double-emulsion microcapsules, DEMs). OTC.HEM was most efficiently
encapsulated (7.4 mg core/l00 mg lipid) and retained (66% of initial encapsulated core
material remained after 24 hours suspension in seawater) as a particulate in SMs. SMs
containing OTC.HEM were most stable in storage, retaining 86% of their core after 5
weeks of storage as a wet paste. Freeze-drying of SMs containing particulate OTC.HEM
increased initial leakage losses of core material, but did not the affect the stability of
capsules during long-term storage. Freeze-drying of DEMs containing aqueous
OTC.HCl also increased initial leakage loses of core material, but improved the stability
of DEMs during long-term storage. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28516 |
| Date | 12 December 1994 |
| Creators | Buchal, Michael A. |
| Contributors | Langdon, Christopher J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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