<i>Lactobacillus plantarum</i> and <i>Pediococcus pentosaceus</i> Starter Cultures as a Tool for Microflora Management in Malting and for Enhancement of Malt Processability

Journal of the Institute of Brewing

Peltola³

et al. 2007

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The present study was carried out to investigate the impacts of bacterial and fungal communities on grain germination and on the malting properties of good‐quality two‐row barley. In order to suppress the growth of bacterial and/or fungal communities, various antibiotics were added to the first steeping water of barley. This study was also designed to explore the dynamics of the bacterial community in the malting process after antimicrobial treatments by polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE). The diverse microbial community played an active role in the malting ecosystem. Even previously undescribed bacterial species were found in the malting ecosystem. Suppression of the bacterial community mainly consisting of Gram‐negative bacteria was advantageous with respect to grain germination and wort separation. In addition, more extract was obtained after antibacterial treatments. The fungal community significantly contributed to the production of microbial β‐glucanases and xylanases, and was also involved in proteolysis. An improved understanding of the complex microbial community and its role in malting enables a more controlled process management and the production of high quality malt with tailored properties.

Section: Discussionsupporting

confidence: 91%

Indigenous Microbial Community of Barley Greatly Influences Grain Germination and Malt Quality

Journal of the Institute of Brewing

Peltola³

et al. 2007

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“…It has been shown that a speciWc microbial community develops in each malting plant [51,52]. Furthermore, the yeast community present in the malting process depends on the initial population of barley, interactions between the diVerent microbial groups, process conditions such as temperature and aeration, and the use of antimicrobial treatments such as starter cultures [25,43,49,52].…”

Section: Resultsmentioning

confidence: 99%

“…Some yeasts normally associated with malting have shown strong antagonistic activity and have been applied as natural biocontrol agents to restrict the growth of harmful fungi [6,17]. Our previous studies with lactic acid starter cultures revealed that the addition of lactic acid bacteria (LAB) into the steeping activated the indigenous yeast community and enhanced the production of microbial -glucanase and xylanase in the malting process 43]. However, the source of these microbial enzymes was unknown, and we suggested that enhanced growth of the yeast community could partly explain the increased enzyme activities.…”

Section: Introductionmentioning

confidence: 99%

Yeasts in an industrial malting ecosystem

Wilhelmson

J Ind Microbiol Biotechnol

et al. 2006

The malting ecosystem consists of two components: the germinating cereal grains and the complex microbial community. Yeasts and yeast-like fungi are an important part of this ecosystem, but the composition and the effects of this microbial group have been largely unknown. In this study we surveyed the development of yeasts and yeast-like fungi in four industrial scale malting processes. A total of 136 malting process samples were collected and examined for the presence of yeasts growing at 15, 25 and 37 degrees C. More than 700 colonies were isolated and characterized. The isolates were discriminated by PCR-fingerprinting with microsatellite primer (M13). Yeasts representing different fingerprint types were identified by sequence analysis of the D1/D2 domain of the 26S rRNA gene. Furthermore, identified yeasts were screened for the production of alpha-amylase, beta-glucanase, cellulase and xylanase. A numerous and diverse yeast community consisting of both ascomycetous (25) and basidiomycetous (18) species was detected in the various stages of the malting process. The most frequently isolated ascomycetous yeasts belonged to the genera Candida, Clavispora, Galactomyces, Hanseniaspora, Issatchenkia, Pichia, Saccharomyces and Williopsis and the basidiomycetous yeasts to Bulleromyces, Filobasidium, Cryptococcus, Rhodotorula, Sporobolomyces and Trichosporon. In addition, two ascomycetous yeast-like fungi (black yeasts) belonging to the genera Aureobasidium and Exophiala were commonly detected. Yeasts and yeast-like fungi produced extracellular hydrolytic enzymes with a potentially positive contribution to the malt enzyme spectrum. Knowledge of the microbial diversity provides a basis for microflora management and understanding of the role of microbes in the cereal germination process.

“…Yeast and lactic acid bacteria often occurring together in plant-based bioprocesses and synergistic interactions between these two groups are utilized in many cereal fermentations [4]. We have previously shown that the addition of lactic acid bacteria (LAB) into malting activated the indigenous yeast community and enhanced production of microbial -glucanase and xylanase in the malting process [34]. Combining antagonistic yeast with lactic acid bacteria might further enhance the usefulness of starter technology in complex bioprocesses such as malting.…”

Section: Introductionmentioning

confidence: 99%

Yeasts isolated from industrial maltings can suppress Fusarium growth and formation of gushing factors

Sarlin

J Ind Microbiol Biotechnol

et al. 2007

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Fusarium infection of barley and malt can cause severe problems in the malting and brewing industry. In addition to being potential mycotoxin producers, Fusarium fungi are known to cause beer gushing (spontaneous overfoaming of beer). Cereal-derived bacteria and yeasts are potential biocontrol agents. In this study, the antifungal potential of selected yeasts (12 strains) derived from the industrial malting ecosystem was studied in vitro with a plate-screening assay. Several ascomycetous yeast strains showed antagonistic activity against field and storage moulds, Pichia anomala being the most effective strain. The effects of P. anomala VTT C-04565 (C565) were examined in laboratory scale malting with naturally contaminated barley exhibiting gushing potential. P. anomala C565 restricted Fusarium growth and hydrophobin production during malting and prevented beer gushing. Grain germination was not disturbed by the presence of yeast. Addition of P. anomala C565 into the steeping seemed to retard wort filtration, but the filtration performance was recovered when yeast culture was combined with Lactobacillus plantarum VTT E-78076. Well-characterized microbial cultures could be used as food-grade biocontrol agents and they offer a natural tool for tailoring of malt properties.