Isolamento e caracterização de bactérias ácido láticas obtidas de carne ovina e aplicação de substâncias antimicrobianas em linguiça ovina frescal no controle de Listeria monocytogenes Scott A

Abstract

The application of lactic acid bacteria (LAB) and/or their antimicrobial metabolites (such as bacteriocins) in food products, capable of inhibiting the multiplication of undesirable (deteriorating and/or pathogenic) microorganisms, is a strategy increasingly studied and used in food biopreservation. In the manufacture of meat products, a good option is the use of meat obtained from animals with advanced age, among which we highlight the sheep meat. Based on this, the objective of this work was to isolate and characterize lactic acid bacteria obtained from sheep meat and evaluate the application of antimicrobial substances synthesized by these bacteria in fresh sheep sausage in the control of Listeria monocytogenes. A total of 84 LAB were isolated, of which six presented bacteriocinogenic activity in the Cell Free Supernatant (CFS) against Listeria monocytogenes Scott A, besides having proteinaceous nature and microbiologically safe, confirmed by the absence of the enzymes gelatinase, DNase, hemolytic activity and sensibility to some antimicrobials for clinical use. The antimicrobial substances showed stability at different temperatures, pH values and in the presence of salt (NaCl) and curing salts. In addition, they did not show cytotoxicity at dilutions higher than 1:40. The six isolates selected were identified as Streptococcus gallolyticus (3) and Enterococcus faecium (3), with antimicrobial activities ranging from 200 to 3.200 AU.mL-1. Only the Enterococcus faecium EO1 isolate showed genes that encode enterocin A, with maximum production of the antimicrobial substance from 6 hours, during the exponential phase of growth of the microorganism. The application of 5% and 10% of CFS obtained from E. faecium EO1 in fresh sheep sausage was significantly effective in inhibiting L. monocytogenes Scott A inoculated into the product, with difference of 1 log cycle, up to 21 days under refrigerated storage, even though the presence of some ingredients in sausage, such as fat and sheep meat, may have influenced the diffusion of CFS into the product. It was possible to isolate LAB with bacteriocinogenic potential from fresh sheep meat and fresh sheep sausage can be considered as a good vehicle for the incorporation of CFS from E. faecium EO1 with antimicrobial activity. Key