Antimikrobna aktivnost probiotičkih sojeva Lactobacillus vrsta

master's thesis

• Title (english): Antimicrobial activity of probiotic Lactobacillus strains
• Author: Vida Lonić
• Mentor: Jasna Beganović (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for Antibiotic, Enzyme, Probiotic and Starter Cultures Technology); Zagreb
• Defense date and country: 2010-12-21, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

Bakterijski sojevi roda Lactobacillus najčešći su producenti bakteriocina među bakterijama mliječne kiseline (BMK). Stoga je u ovom radu ispitana antimikrobna aktivnost probiotičkih sojeva Lactobacillus fermentum A8, Lactobacillus helveticus M92 i Lactobacillus plantarum L4 s osobitim osvrtom na njihovo bakteriocinsko djelovanje. Biosinteza bakteriocina pomoću probiotičkih sojeva doprinosi kolonizaciji intestinalnih epitelnih stanica domaćina i njegovoj zaštiti od patogena u kompetitivnom okolišu gastrointestinalnog trakta što su sve važna funkcionalna svojstva probiotičkih bakterija. Antimikrobna aktivnost supernatanata kultura, prema različitim test mikroorganizmima, ispitana je prije i nakon podešavanja pH vrijednosti na 6.5, kako bi se uklonio inhibicijski učinak mliječne kiseline, te ispitala mogućnost biosinteze bakteriocina. Pri tome su korištene turbidimetrijska metoda, metoda difuzije iz jažica u agar i metoda dvostrukog sloja agara. Prema dosadašnjim istraživanjima, prisutnost i združeni uzgoj bakteriocin- osjetljivog mikroorganizma i mikroorganizma producenta bakteriocina potiče biosintezu bakteriocina. Stoga je, istražena i mogućnost induciranja biosinteze bakteriocina živim stanicama bakterije Lactococcus lactis subsp. lactis LMG 9450, stanicama Lact. lactis subsp. lactis LMG 9450 koje su prethodno inaktivirane pri 100 °C, kao i supernatantom kulture ove BMK. Ispitana je i prisutnost gena koji kodiraju za bakteriocine pomoću lančane reakcije polimerazom uz primjenu specifičnih početnica. Dobiveni rezultati ukazuju na mogućnost indukcije bakteriocinske aktivnosti odabranih probiotičkih sojeva živim stanicama Lact. lactis subsp lactis LMG 9450, te na prisutnost gena plnJ koji kodira za bakteriocin soja L. fermentum A8.

Abstract (english)

Majority of bacteriocins described between lactic acid bacteria (LAB) are those produced by Lactobacillus spp. Hence, the objective of this thesis was to investigate the antimicrobial activity of probiotic strains Lactobacillus fermentum A8, Lactobacillus helveticus M92 and Lactobacillus plantarum L4 with the special interest for their bactericinogenic activity. Bacteriocin biosynthesis by probiotic strains contributes to the colonisation resistance of the host, its protection against gastrointestinal pathogens and facilitates the establishment of a probiotic strain in the competitive environment of the gut, which are all important probiotic characteristics. Antimicrobial activity of the culture supernatants was examined, before and after adjusting of pH value to 6.5, in order to eliminate the inhibitory effect of lactic acid and investigate the possibility of bacteriocin biosynthesis. In this experiments turbidimetric, agar well diffusion and double-layer agar method were applied. According to the literature, the presence and close contact of competing microorganism is important environmental factor for bacteriocin biosynthesis. Hence, the possibility of the induction of bacteriocin biosynthesis by probiotic cells, after the cocultivation with Lactoccocus lactis subsp. lactis LMG 9450 cells or Lact. lactis subsp. lactis LMG 9450 cells inactivated by boiling at 100 °C, as well as using culture supernatants of the probiotic strains, was investigated. The detection of the different genes coding for bacteriocins was examined by PCR amplification of the specific primers. Results suggest on the possibility of the induction of bacteriocin biosynthesis by metabolically active Lact. lactis subsp. lactis LMG 9450 cells and ond the presence of gene plnJ responsible for bacteriocin expression in L. fermentum A8.

• Keywords: antimikrobno djelovanje; Lactobacillus; bakteriocini; induciranje biosinteze bakteriocina; probiotici
• Keywords (english): antimicrobial activity; bacteriocins; induction of bacteriocin biosynthesis; probiotics
• Language: croatian
• URN:NBN: urn:nbn:hr:159:958481
• Study programme: Title: Biotechnology; specializations in: Biochemical Engineering; Course: Biochemical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer biotehnologije; smjer biokemijsko inženjerstvo (diplomirani inženjer biotehnologije; smjer biokemijsko inženjerstvo)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-08-28 12:32:20