Banca de DEFESA: Carla Azevedo Bilac

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Carla Azevedo Bilac
DATE: 07/02/2024
TIME: 14:00
LOCAL: Plataforma Teams
TITLE:

Water kefir: analysis of bioactive compounds and genetic identification of microorganisms with inhibitory
activity against pathogenic strains

KEY WORDS:

kefir; antioxidant activity, antimicrobial activity, acetic acid bacteria, lactic acid bacteria, yeast.

PAGES: 121
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

Water kefir is a drink resulting from the fermentation process by microorganisms present in kefir grains and
has probiotic properties. The aim of this study was to evaluate the antimicrobial capacity and genetically
identify the microorganisms isolated from water kefir, in addition to analyzing the physical-chemical aspects
of the drink. To produce kefir, 10% (w/v) of kefir grains were added to a solution of water and brown sugar
at 5ºBrix and fermentation occurred for 24 and 48 h at 30°C. After the fermentation process, analyzes were
carried out to determine pH, acidity, sugars, and phenolic compounds. The antioxidant activity was
evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2 ́-azino-bis-3-ethylbenzothiazoline-6-asulfonic acid) methods. For the isolation of microorganisms from kefir, the samples were
seeded on Yeast Malt (YM) agar, All Purpose Tween agar, M17 agar, Man, Rogosa and Sharpe agar and
Hestrin-Schamm agar, incubated at 28°C and after 48 h, colonies with different morphologies were isolated.
To test antimicrobial activity, 5 mm agar discs containing microorganisms isolated from kefir were placed
on YM agar plates previously plated with Acinetobacter baumannii ATCC 19606, Pseudomonas aeruginosa
ATCC 9027, Enterococcus faecalis ATCC 51299 and Listeria monocytogenes ATCC 7644. After 24 h of
incubation at 37°C, bacterial growth inhibition zones (in millimeters in diameter) were measured. The
genetic identification of microorganisms was carried out by DNA sequencing of the V3/V4 region of the 16S
rRNA gene for bacteria and the ITS1 ribosomal spacer region for yeast. Water kefir in 48 h presented a pH
of 3.69, 0.50% acidity, 3.43% total sugars, 1.40 GAE g.L-1 of phenolic compounds and antioxidant activity
of 57.8 mM TE.100 mL-1 by the DPPH method and 227,16 mM.100 mL-1 TEAC by the ABTS method. Of
the 104 microorganisms isolated from kefir, 76 (73.07%) exhibited inhibition against A. baumannii (11.28
to 32.63 mm), 66 (63.46%) against P. aeruginosa (10.81 to 26.87 mm), 76 (73.07%) against E. faecalis
(7.57 to 29.35 mm) and 56 (53.84%) against L. monocytogenes (10.77 to 27.93 mm). Genetic sequencing
of 40 kefir microorganisms identified 65.0% acetic acid bacteria (AAB), 17.5% lactic acid bacteria (LAB)
and 15% yeast. The AAB were composed of the genera Gluconabacter, Acetobacter and
Komagataeibacter; LAB were identified as Lactobacillus and yeasts were identified as Brettanomyces,
Hanseniaspora, Pichia and Saccharomyces cerevisiae.

COMMITTEE MEMBERS:
Presidente - 1697332 - DANIELA CASTILHO ORSI
Externo ao Programa - 1880131 - GUILHERME MARTINS GELFUSO - nullExterna à Instituição - VANIA SILVA CARVALHO - IFGOIANO