PROBIOTIC POTENTIAL OF BACTERIAL ISOLATES FROM KEFIR

INTRODUCTION: Kefir consists of a complex mix of microorganisms, primarily lactic acid bacteria, which, when administered in appropriate quantities, can offer health benefits to the host. The growing interest in probiotic foods like kefir has led to a significant increase in scientific studies on the topic. However, the field of probiotics is still largely unexplored, especially given the extensive biodiversity of microorganisms in kefir. This makes in vitro probiotic tests crucial for ensuring consumer safety and evaluating probiotic parameters. AIMS: This project aims to determine the probiotic potential of bacterial isolates from kefir through in vitro methods, with the goal of developing new functional foods in the future. MATERIALS AND METHODS: A storage bank was developed from 5 samples of kefir donations, resulting in a total of 480 bacterial isolates. Due to the large number of isolates, a preliminary screening was conducted using presumptive identification tests (Gram staining, catalase, and oxidase) and exclusion tests (hemolytic activity and antibiotic sensitivity). Ten isolates were selected that matched the characteristics of lactic acid bacteria (LAB)—positive for Gram staining and negative for catalase, oxidase, and hemolytic activity tests. These selected isolates then underwent in vitro tests to determine their probiotic potential, including autoaggregation, coaggregation, hydrophobicity, and biofilm formation. Additional tests for antimicrobial activity, pH resistance, pancreatin resistance, pepsin resistance, and bile salt resistance are planned. RESULTS: The phenotypic tests yielded satisfactory results, allowing for the precise selection of isolates. Out of 480 samples, 52 were Gram-positive, 229 were catalase-negative, and 472 were oxidase-negative. Generally, the isolates exhibited low values for autoaggregation and coaggregation tests, low to moderate percentages for hydrophobicity, showed adhesion in the biofilm test, and were susceptible to three of the six tested antibiotics. FINAL CONSIDERATIONS: The research project was beneficial in several aspects, following a logical sequence of steps that led to successful results. The preliminary screening made the selection of isolates for probiotic testing more precise and reliable. All tests performed so far are considered fundamental for probiotic evaluation. The obtained results are essential for the project’s scope and provide guidance for future research. However, it is crucial to conduct additional in vitro tests simulating gastrointestinal conditions to demonstrate the potential probiotic benefits of the isolates.

KEYWORDS: 1. Kefir; 2. probiotic potential; 3. in vitro tests; 4. lactic acid bacteria.