Banca de QUALIFICAÇÃO: ANA ERUNDINA DE LUNA MORAES LEITE

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANA ERUNDINA DE LUNA MORAES LEITE
DATE: 27/02/2026
TIME: 14:00
LOCAL: Plataforma Google Meet - https://meet.google.com/una-gfyu-wir
TITLE:

Prospecting lactic acid bacteria isolated from raw milk: safety assessment and technological characterization

KEY WORDS:

Protective cultures; Microbiological safety; Functional characterization; Biotechnological application

PAGES: 85
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUMMARY:

Lactic acid bacteria (LAB) play a fundamental role in food fermentation, contributing to microbiological safety, preservation, sensory quality, and the development of functional foods. Beyond their traditional use, these bacteria are recognized for their ability to produce antimicrobial metabolites, such as bacteriocins and organic acids, which are effective against pathogenic and spoilage microorganisms. In this context, raw milk represents an important source of microbial diversity, enabling the selection of LAB strains with technological and probiotic potential, provided that their safety is properly evaluated. The aim of this study was to isolate, identify, and characterize lactic acid bacteria obtained from raw milk, assessing their antimicrobial activity, safety for the host, and technological properties, with a view to their application as protective and/or probiotic cultures in dairy products. Raw milk samples were collected from rural farms in the state of Pernambuco, Brazil, and subjected to isolation on MRS medium. The isolates were initially characterized based on morphological features, Gram staining, and catalase activity, and subsequently identified by MALDI-TOF mass spectrometry and PCR amplification of the 16S rRNA gene. Genetic diversity among the isolates was evaluated using RAPD-PCR, allowing the selection of genetically distinct strains. The antimicrobial activity of selected strains was evaluated against indicator microorganisms using agar diffusion assays, as well as the stability of the antimicrobial compounds under different pH conditions, heat treatments, and enzyme exposure. Strains belonging mainly to the genera Enterococcus and Streptococcus exhibited relevant antimicrobial activity, maintaining inhibitory effects even after physicochemical treatments, indicating their potential technological robustness. Safety assessment included cytotoxicity assays using human intestinal Caco-2 cells, hemolytic activity tests, and antibiotic susceptibility profiling. The results demonstrated absence of hemolytic activity, low cytotoxicity, and antibiotic susceptibility profiles consistent with safety criteria for probiotic candidates. In addition, functional properties such as adhesion to Caco-2 cells and tolerance to simulated gastrointestinal conditions were evaluated. Technological properties relevant to industrial application were also investigated, including tolerance to different sodium chloride concentrations and the production of enzymes of industrial interest, such as proteases, β-galactosidase, and amylase. Overall, the results indicate that lactic acid bacteria isolated from raw milk exhibit promising potential for use as protective and/or probiotic cultures, provided that strict safety criteria are met. This study contributes to the valorization of raw milk microbiota and supports the development of innovative strategies to improve the quality and safety of dairy products.

COMMITTEE MEMBERS:
Presidente - ***.569.911-** - KEILA APARECIDA MOREIRA - UFRPE
Externo ao Programa - ***.100.444-** - LEANDRO FRAGOSO LINS - UFRPE
Externa à Instituição - ELIZABETE RODRIGUES DA SILVA