Protective effect of lysozyme‐galactomannan or lysozyme‐palmitic acid conjugates against Edwardsiella tarda infection in carp, Cyprinus carpio L

Abstract

The protective effect of lysozyme-galactomannan or lysozyme-palmitic acid conjugates orally administered to carp, Cyprinus carpio L. was investigated using a virulent strain of Gram-negative EdwardsieUa tarda isolated from an infected fish. Lysozyme-galactomannan conjugate was prepared through controlled Maillard reaction. Lysozyme-palmitic acid conjugate was prepared through base-catalyzed ester exchange using Nhydroxysuccinimide ester of palmitic acid. The conjugates provided substantial protection to carp infected with a Gramnegative bacteria f'Lsh pathogen E. tarda NG 8104. Lytic activities of lysozyme conjugates with galactomannan and palmitic acid were about 80 and 71% of native lysozyme using Micrococcus lysodeikticus as a substrate. Feeding with lysozyme conjugates, for 8 days, significantly enhanced fish protection against E. tarda infection. The survival rate was 30% for lysozyme-galactomannan conjugate treated fish and 20% for lysozyme-palmitic acid conjugate treated fish after 6 days cultivation while all control fish died within 3 days. On the other hand, a recovery rate of 40% after 6 days was observed in the fish group that were fed lysozyme-palmitic acid conjugate 3 and 2 h before and after E. tarda challenge, respectively, and for 6 consecutive days. The results of this work show the possibility of utilizing lysozyme conjugates with galactomannan or palmitic acid as a therapeutic for infection in fish.

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“…The diffused bands in SDS-PAGE further confirm the formation of conjugated products with wide distribution of molecular weights. Similar results have been reported by other investigators 9,[15][16][17][18][19][20] .…”

Effect of conjugation with glucosamine on the functional properties of lysozyme and casein

“…It is probable that some carboxyl groups of caseins were also activated by EDC and reacted with amino groups of other protein molecules, resulting in intermolecular covalent crosslinking. The formation of such electrophoretic patterns has been reported previously for various polysaccharides attached to lysozyme, 10,15,21 gluten, 12 ovalbumin, 13 soybean proteins 42 and β-lactoglobulin.…”

“…In an effort to expand the antibacterial activity of lysozyme to Gram-negatives, lysozyme derivatives have been prepared by covalent attachment of polysaccharides (galactomannan and dextran) or fatty acids to lysozyme. 10,11 A number of chemical methods for the attachment of carbohydrates to proteins have been reported. These include coupling through Maillardbased reaction, 8,11 -16 reductive alkylation 17 -20 and carbodiimide-promoted amide formation.…”

Multi-functional biopolymer prepared by covalent attachment of galactomannan to egg-white proteins through naturally occurring Maillard reaction

“…In a separate set of experiments, lysozyme conjugates were orally administered to the acclimatized carps 3 h before and 2 h after the intra-peritoneal infection with 2.1610 8 CFU N 100 g -1 of E. tarda, respectively. The fish were subsequently fed with a pelleted food containing lysozyme conjugates at a dosage of 40 mg N kg -1 N day -1 and survivors were examined for 6 days in a similar manner as above [14].…”

“…Attachment of fatty acids to lysozyme is important for its bactericidal effect against E. tarda by interaction with and subsequent insertion into the outer membrane of Gramnegative bacteria [14]. Although antimicrobial drugs have been employed for prophylactic and therapeutic purposes, recent occurrence of drug-resistant strains has made treatment with antibiotics more difficult.…”