| Congresso Brasileiro de Microbiologia 2023 | Resumo: 447-1 | ||||
Resumo:Lactic acid bacterias (LABs) have fermentative metabolism converting sugars into acids, act as probiotics bringing benefits to the intestinal microbiota of animals and humans and produce antimicrobial compounds such as organic acids and bacteriocins. Bacteriocins are antimicrobial peptides with a broad inhibitory spectrum and therapeutic potential, inhibiting the development of deteriorating and pathogenic microorganisms. The genus Lactobacillus represents most of the group of BALs and Lactobacillus rhamnosus is a species that has the ability to survive and grow in acidic pH, is capable of producing proteins that are efficient in inhibiting pathogens. Staphylococcus aureus naturally inhabits the skin and mucous membranes of humans, is involved in several outbreaks of Foodborne Pathogen Diseases (FPD) due to the production of enterotoxins. The ultrafiltered cheese has a higher amount of whey proteins, due to the ultrafiltration process when compared to the cheese obtained by the conventional process, so it was chosen as a good food matrix, rich in nutrients. Thus, this work aimed to evaluate the interaction and growth inhibition between Lactobacillus rhamnosus (LR) isolated from raw milk of healthy cows, against a strain of S. aureus (SA) isolated from the same source in ultrafiltered cheese acquired in the trade of Campinas - SP. In a previous work, the interaction test was carried out in MRS broth combining the strain of S. aureus with the strain of L. rhamnosus, where a decrease in the count of the pathogen in question was observed. For this work, the same combination was tested in ultrafiltered cheese in order to obtain a discussion about the influence of the food matrix on the interaction of these two microorganisms. Parameters such as water activity (Aw) and hydrogen potential (pH) were also obtained. In the cheese, were inoculated 104 CFU.g-1 of the culture of S. aureus and 106 CFU. g-1 of L. rhamnosus, the cheese portions with the cultures were incubated at 36 °C and the growth of microorganisms was evaluated at different times (0, 4, 8, 12, 24, 36, 48, 72, 96, 120 and 168 hours). Their count was performed by inoculating different dilutions of the cheese in Baird Parker agar to count Staphylococcus spp. and on MRS agar under anaerobiosis for counting L. rhamnosus. In the previous study, in MRS broth test, the activity of L. rhamnosus significantly influenced the growth multiplication of S. aureus, with a reduction of 2 log cycles at 24 h without detection of colonies at 36 h. The reduction of pH in the medium also occurred ranged from 6.97 at time 0 to 4.42 in time 120 hours. However, in cheese, the reduction in the S. aureus count did not occur as expected, since the BAL in question began its decline phase at 48h, with no colonies being detected in the MRS agar from that time onwards, while the S. aureus count increased, maintained between 105 and 107 CFU. g-1 up to 96 hours after incubation. The results can be seen in Figure 1. We can conclude that the food matrix directly influences the behavior of the microorganisms tested, not reflecting the results obtained in the in vitro test, being necessary more studies regarding the individual behavior of these strains in the ultrafiltered cheese. Palavras-chave: bacteriocins, biopreservatives, L. rhamnosus Agência de fomento:CNPq | |||||