| Abstract | Egzopolisaharidi (EPOL) bakterija mliječne kiseline (BMK) imaju značajnu primjenu u prehrambenoj industriji, no u novije vrijeme istražuje se i njihova uloga kao funkcionalnih biomolekula. Stoga je cilj ovog rada bio detektirati sojeve, potencijalne producente EPOL, kod bakterijskih izolata mikrobiote majčinog mlijeka, koja sadrži visoki udio mikrobne populacije BMK i bifidobakterija. Mogućnost biosinteze EPOL kod 60 izolata BMK mikrobiote majčinog mlijeka ispitana je in vitro, detekcijom tipičnog „ropy“ fenotipa. Tri odabrana soja MC1, MC9 i AF7, potencijalna producenta EPOL, koja su pokazala prepoznatljiv, ,,ropy'' fenotip za biosintezu EPOL, taksonomski su identificirani sekvencioniranjem 16S rRNA gena, te je ustanovljeno da se radi o Lactobacillus fermentum MC1 i Enterococcus faecium MC9, dok soj AF7 nije identificiran. S ciljem daljnje karakterizacije odabranih sojeva BMK, ispitana je osjetljivost sojeva na antibiotike, te njihov spektar antimikrobnog djelovanja, što su specifična svojstva značajna za definiranje funkcionalnosti odnosno iskazivanje poželjnih učinaka na zdravlje domaćina. Metodom difuzije u agar s filter diskovima i E-testom ustanovljeno je da Lb. fermentum MC1 i Ec. faecium MC9 pokazuju fenotipski rezistenciju na antibiotik vankomicin, što je tipična karakteristika bakterija iz roda Lactobacillus. Kako je izolat AF7 pokazao višestruku rezistenciju na antibiotike gentamicin, eritromicin, neomicin i streptomicin, isključen je iz daljnih istraživanja. Na temelju vrijednosti efektivnih inhibicijskih omjera (EIR) ustanovljeno je da se odabrani sojevi odlikuju različitim spektrom antimikrobnog djelovanja, koji ne iskazuje značajno inhibicijsko djelovanje prema srodnim bakterijama iz roda Lactobacillus i Enterococcus, a čiji su predstavnici također dio mikrobne populacije majčinog mlijeka. Daljnja istraživanja će se provesti s ciljem karakterizacije funkcionalnosti odabranih bakterija. |
| Abstract (english) | The exopolysaccharides (EPOL) from lactic acid bacteria (LAB) have significant use in the food industry, but recently, their role as functional biomolecules has been proposed. Therefore, the aim of this work was to detect strains, potent EPOL producers, among breast milk microbiota that is characterized by the high abundance of LAB and bifidobacteria. 60 LAB representatives of breast milk microbiota had been evaluated in vitro for potential biosynthesis of EPOL, by the detection of a typical “ropy’’ phenotype. The three selected strains, MC1, MC9 and AF7, which demonstrated a recognizable “ropy” phenotype for the biosynthesis of EPS, were identified as Lactobacillius fermentum MC1 and Enterococcus faecium MC9 by 16S rRNA gene sequencing, while AF7 isolate was not identified. In order to further characterize the selected strains of LAB, their antibiotic susceptibility and the spectrum of antimicrobial activity were examined. These specific properties are important for defining strain functionalities i.e. health-promoting effects. According to the results Lb. fermentum MC1 and Ec. faecium MC9 were found to be phenotypically resistant to vancomycin, which is typical for Lactobacillus genus. Since the AF7 isolate showed multiple resistance to gentamicin, erythromycin, neomycin and streptomycin, it was excluded from further research. The value of effective inhibition ratio (EIR) revealed that selected strains are distinct in their spectrum of antimicrobial activity, which appears not to show significant inhibitory effect on related bacteria from the Lactobacillus and Enterococcus genus, and whose representatives are also part of the microbial population of breast milk. Further research will be carried out to characterize the functionality of the selected bacteria. |
