Caracterização fenotípica, molecular e avaliação do potencial tecnológico de estafilococos coagulase negativa isolada de queijos da região sudoeste do Rio Grande do Sul/Brasil

Abstract

Several studies have been conducted worldwide aiming to isolate CNS from handmade/local products with the intention of characterizing these isolates and verifying their potential to use as starter cultures in fermented sausage. One of the main reasons to explore native biodiversity is to isolate microorganisms adapted to the environmental, ecological and technological conditions that can provide them a greater ability to compete and grow when added to the product. Another important factor is that native flora can have a different enzymatic profile, which produces peculiar characteristics to local products, contributing to the standard of identity for food. Few researchers have explored the biodiversity of CNS in dairy products. The current study aimed to characterize and evaluate the technological potential and safety aspects of coagulase-negative staphylococci (CNS) isolated from cheeses. The technological potential, as well as the microbiological and toxicological safety, were evaluated by phenotypic and molecular analysis. It were possible to characterize and identify phenotypically 17 isolates as Gram-positive, catalasepositive and coagulase-negative cocci. The isolates were identify as Staphylococcus saprophyticus (n=14), Staphylococcus xylosus (n=2) and Staphylococcus cohnii subsp. urealyticus (n=1) by Vitek system. After molecular identification, only one isolate, LQ3, was confirmed as S. xylosus. The results showed that S. xylosus LQ3 harboured lipolytic, proteolytic, nitrate reductase (25 and 37 °C) and superoxide dismutase (9.43 ± 1.43%) activity. Isolate LQ3 showed microbiological and toxicological safety as the results obtained. Furthermore, LQ3 was sensitive to all antimicrobials tested and did not show any antimicrobial resistance gene or hemolytic and DNase activity. No genes encoding for classical staphylococcal enterotoxins, histidine decarboxylase (hdc) and tyrosine decarboxylase (tyrdc) were identified. Staphylococcus xylosus LQ3 showed promising potential due to the good technological properties identified, as well as, the safety aspects. In thefuture, this isolate could be applied as a starter culture for meat sausage production.