Effet biopréservateur du chitosane associé à des substances protéiques antimicrobiennes dans le cas des produits marins

Abstract

The objective of this study was to develop a biopreservation strategy of the royal pink shrimp Penaeus braziliensis by either using antagonistic substances produced by lactic acid bacteria, , Lactobacillus plantarum, isolated from the same shellfish; using a biopolymer extracted from Crustacean Shells known as chitoan; or by the combination of both of them. First of all, bacterial species were isolated from the shrimps and identified by PCR: Lb. plantarum, Lb. Brevis, Enterococcus faecalis, Pediococcus pentosaceus, Leuconostoc et Weissella paramesenteroïdes. One psychrophile strain, Lb. plantarum Lbr1, was selected based on its high antagonistic activities against some pathogenic strains (inhibition zones comprised between 15.7 and 23.83 mm). This strain is able to produce lactic acid (18g / L / 24h) and a protein factor inhibitor (SANA1) that resists to temperatures of 100 ° C for 20 min. Secondly, chitosan extracted from shrimp shells was characterized in terms of the degree of deacetylation (75%), viscosity (119.7±0.04 Pa.s) , molecular weight (1414.33±16.99 kDa), ash content (0.34g/g of chitosan), dry matter (0.74±0.02 g /g of chitosan) and protein content (0.37g/g of chitosan). The chitosan ability to reduce DPPH (62.6%) and its antimicrobial activity was also studied. A remarkable inhibition zones were obtained against Staphylococcus aureus STRM (28 mm), E. coli CIP76.24 (14 mm), Bacillus subtilis DSMZ10 (15.83 mm), Salmonella enterica CIP81.3 (18.66 mm), Shewanella putrefaciens EU2187 (25.66 mm) and Listeria monocytogenes (21.66 mm). The chelating properties of chitosan (3, 6 and 9 ppm) were 80.33, 82.50 and 86.22% with manganese, 51.44, 53.63 and 45.77% with nickel and 66.53, 51.70 and 66% with the zinc, respectively. Finally, the preservative effect of the chitosan biofilm alone, the protein factor SLbr1 alone or both of them combined chitosan / SLbr1 on shrimp inoculated with Staphylococcus aureus STRM and stored for three weeks at 4 ° C was remarkably effective and a inhibition of 99% of this pathogenic strain was obtained. In the same time, the organoleptic characteristics of the shrimp were not affected.