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J Ind Microbiol Biotechnol (2012) 39:18211832 DOI 10.1007/s10295-012-1188-8
ENVIRONMENTAL MICROBIOLOGY
TRFLP analysis reveals that fungi rather than bacteriaare associated with premature yeast occulation in brewing
Mandeep Kaur John P. Bowman Doug C. Stewart
Megan Sheehy Agnieszka Janusz R. Alex Speers
Anthony Koutoulis David E. Evans
Received: 25 May 2012 / Accepted: 10 August 2012 / Published online: 28 August 2012 Society for Industrial Microbiology and Biotechnology 2012
Abstract Premature yeast occulation (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 ngerprinting 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 ngerprint 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 360460 bp size range, for fungal HaeIII restriction enzyme-derived TRFLP proles appeared to vary substantially between PYF ?ve and PYF -ve samples. The source of the barley malt did not inuence 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 360460 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 efcient and viable alternative for monitoring PYF during brewery fermentations.
Keywords Barley malt Brewery fermentation
Community ngerprinting Microbial communities Yeast
Introduction
Representing an important process in the fermentation of brewers wort into beer, yeast occulation has been intensively studied and is well understood [6, 41, 4347, 51]. However, the understanding of the phenomenon of premature yeast occulation (PYF) lags behind, despite it being studied for over 40 years. PYF is an intermittent issue in the brewing industry that results in incomplete utilization of fermentable sugars in the wort, resulting in out of specication beer and disrupted brewing production schedules, leading to signicant economic losses for the effected brewer [4].
Several substances in the wort derived from malt, particularly the barley...