Fiziološka karakterizacija bakterija mlečne kiseline izolovanih iz autohtonog sira jugoistočne Srbije i evaluacija njihovih biotičkih potencijala

U ovom rukopisu, ispitano je i utvrđeno prisustvo i fiziološke karakteristike bakterija mlečne kiseline (BMK) izolovanih iz tradicionalno proizvedenog sira iz jugoistočne Srbije (područje Sokobanje). Tri uzorka, iz različitih seoskih domaćinstava, uzorkovana su tokom proleća, leta i jeseni. Ispitane su hemijske karakteristike uzoraka sira. Identifikacija BMK je izvršena korišćenjem biohemijskih testova i MALDI-TOF masene spektrofotometrije. Utvrđen je antimikrobni potencijal u odnosu na rast Escherichia coli ATCC 25922 i Proteus mirabilis ATCC 12453, kao i na rast nekih Gram-negativnih bakterija, izolovanih iz istog sira (Klebsiella oxytoca KGPMF1, Klebsiella ornithinolytica KGPMF8 i Aeromonas hydrophila KGPMF64), korišćenjem metode difuzije iz bunarića u agar. Za dalje istraživanje, odabrano je 16 izolata, na osnovu prethodno istraženih i utvrđenih biohemijskih karakteristika i antimikrobnog potencijala u odnosu na izabrane enterobakterije. Izvršena je procena probiotskog potencijala odabranih BMK (tolerancija na različite gastrointestinalne uslove i osetljivost na klinički relevantne antimikrobne agense). Ispitan je uticaj različitih vrsta šećera na rast izolovanih BMK, sposobnost formiranja biofilma, sposobnost bakterija da se vezuju za rastvarače i epitelne ćelije tankog creva svinje, kao i sposobnost auto- i koagregacije između njih i kliničkog izolata Escherichia coli. Aktivnost enzima (kisela i alkalna invertaza, alkalna fosfataza, alkalna proteaza, invertaza) kao i ukupna koncentracija proteina u fermentacionoj tečnosti je izmerena spektrofotometrijskom metodom. Procenjen je uticaj različitih temperatura u sinergizmu sa različitim pH i koncentracijama soli na planktonski rast izolata BMK. Prema procentu masnoće u suvoj materiji, sokobanjski sir pripada punomasnoj grupi sireva, dok prema sadržaju vlage u materiji bez masnoće, sokobanjski sir pripada kiseloj grupi sireva. Brojnost bakterija je zavisila od sezone, domaćinstva i vrste podloge koja se koristila z
In this paper, the presence and physiological characteristics of lactic acid bacteria (LAB) isolated from traditionally made cheese from Southeastern Serbia (Sokobanja area) were examined. Three samples, from different households, were obtained during the spring, summer and autumn. Chemical characteristics of cheese samples were examined. Identification of LABs was done by using the biochemical tests and MALDI-TOF mass spectrometry. The antimicrobial potential on the growth of Escherichia coli ATCC 25922 and Proteus mirabilis ATCC12453 as well as on the growth of some Gram‐negative bacteria, isolated from the same cheese (Klebsiella oxytoca KGPMF1, Klebsiella ornithinolytica KGPMF8 and Aeromonas hydrophila KGPMF64) was examined by using agar-well diffusion method. The 16 isolates were chosen for further investigation, according to the previously investigated biochemical characteristics and antagonistic potential against enterobacteria isolated from the same cheese. The evaluation of the probiotic potential of chosen LABs (tolerance to different gastrointestinal conditions and sensitivity to clinically relevant antimicrobial agents) was evaluated. The effect of different type of sugars on the growth of isolated LAB, was examined. The ability of biofilm formation of LAB, the ability of bacteria to adhere to solvents and to pig intestinal epithelium, as well as the ability of auto- and co-aggregation between them and Escherichia coli clinical isolate, were investigated. The enzymatic activities (acid and alkaline invertase, alkaline phosphatase, alkaline protease, invertase) as well as the total concentration of protein in fermentation liquid were measured by using the spectrophotometry method. The effect of different temperature in synergism with different pH and salt concentration, on the ability of planktonic growth of selected LAB, was also evaluated. According to the fat in dry matter, the cheese belong to full-fat, while according to moisture in nonfat substance