The objective of our study was to purify lysozyme from the fluid filling cavity (shell liquor) of the eastern oysters (Crassostrea virginica) and determine the antimicrobial activity of purified lysozyme against foodborne pathogens in smoked salmon samples.
Oyster shell liquor was collected over four seasons namely summer 2003, fall 2003, winter 2004, and spring 2004. Spring season showed the highest lysozyme concentration. Lysozyme was purified from 300 liters of oyster shell liquor by a two-step ion exchange chromatography using SP- and CM- Sepharose Fast Flow columns, respectively. Two hundred five mg of pure lysozyme was obtained which represented a recovery of 11.1%. The purity and molecular size of the isolated lysozyme showed a single band of about 18 KDa by SDS-PAGE.
MIC assays of the oyster lysozyme were carried out by serially diluting oyster and hen egg white lysozyme to get a concentration range of 160-2.5μg/ml. Twenty four hours bacterial suspension, Brain heart Infusion or APT broth (as required) was added to each well of a 96-well plate followed by incubating the microtiter plates and measuring absorbance at 640 nm with a microplate reader. MIC results showed that oyster lysozyme had antimicrobial activity against both gram-positive and gram-negative bacteria causing food spoilage and poisoning.
Smoked salmon samples were cut into 1 g pieces, inoculated with 24 h broth cultures of L. monocytogenes and S. anatum, dipped into zein propylene glycol, 0.75% agar gel, and calcium alginate coating. Calcium alginate coating was chosen as the best coating out of the three coatings. Various treatments of calcium alginate edible coatings were incorporated with oyster lysozyme or hen egg white lysozyme on the surface of the smoked salmon, allowed to air dry for 20 min and refrigerated at 4°C. Bacterial counts were determined at 0, 7, 14, 21, 28, and 35 days at 37°C for 24 h and CFU/g were determined. Combination of 160 μg/ml of oyster lysozyme and 1000 IU/g of nisin treatment was found to be the most effective treatment and was shown to retain its antimicrobial activity inside the calcium alginate coating for 35 day period.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-07142005-092131 |
| Date | 18 July 2005 |
| Creators | Datta, Shreya |
| Contributors | Marlene Janes, Jerome La Peyre, Jack Losso, Witoon Prinyawiwatkul |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-07142005-092131/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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