title: TRFLP analysis reveals that fungi rather than bacteria are associated with premature yeast flocculation in brewing.
abstract: Premature yeast flocculation (PYF) is a sporadic fermentation problem in the brewing industry that results in incomplete yeast utilization of fermentable sugars in wort. Culture-independent, PCR-based fingerprinting techniques were applied in this study to identify the associations between the occurrence of the PYF problem during brewery fermentation with barley malt-associated microbial communities (both bacteria and fungi). Striking differences in the microbial DNA fingerprint patterns for fungi between PYF positive (PYF +ve) and negative (PYF -ve) barley malts were observed using the terminal restriction fragment length polymorphism (TRFLP) technique. The presence of terminal restriction fragments (TRFs) of 360-460 bp size range, for fungal HaeIII restriction enzyme-derived TRFLP profiles appeared to vary substantially between PYF +ve and PYF -ve samples. The source of the barley malt did not influence the fungal taxa implicated in PYF. TRFLP analysis indicates bacterial taxa are unlikely to be important in causing PYF. Virtual digestion of fungal sequences tentatively linked HaeIII TRFs in the 360-460 bp size range to a diverse range of yeast/yeast-like species. Findings from this study suggest that direct monitoring of barley malt samples using molecular methods could potentially be an efficient and viable alternative for monitoring PYF during brewery fermentations.
authors.affiliation: Food Safety Centre, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, TAS, Australia. mandeepk@utas.edu.au
authors.forename: Mandeep
authors.initials: M
authors.lastname: Kaur
authors.forename: John P
authors.initials: JP
authors.lastname: Bowman
authors.forename: Doug C
authors.initials: DC
authors.lastname: Stewart
authors.forename: Megan
authors.initials: M
authors.lastname: Sheehy
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Janusz
authors.forename: R Alex
authors.initials: RA
authors.lastname: Speers
authors.forename: Anthony
authors.initials: A
authors.lastname: Koutoulis
authors.forename: David E
authors.initials: DE
authors.lastname: Evans
mesh_terms: D001419:Bacteria / Q000166:cytology / Q000235:genetics* / Q000302:isolation & purification; D044822:Biodiversity; D016172:DNA Fingerprinting; D005285:Fermentation; D005427:Flocculation; D005658:Fungi / Q000166:cytology* / Q000235:genetics* / Q000302:isolation & purification; D001467:Hordeum / Q000378:metabolism / Q000382:microbiology; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S