Résumé:
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.
