Brettanomyces Yeasts — from Spoilage Organisms to Valuable Contributors to Industrial Fermentations
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International Journal of Food Microbiology 206 (2015) 24–38 Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro Brettanomyces yeasts — From spoilage organisms to valuable contributors to industrial fermentations Jan Steensels a,b, Luk Daenen c, Philippe Malcorps c, Guy Derdelinckx d, Hubert Verachtert d, Kevin J. Verstrepen a,b,⁎ a Laboratory for Genetics and Genomics, Department of Microbial and Molecular Systems (M2S), Centre of Microbial and Plant Genetics (CMPG), KU Leuven, Kasteelpark Arenberg 22, 3001 Leuven, Belgium b Laboratory for Systems Biology, VIB, Bio-Incubator, Gaston Geenslaan 1, 3001 Leuven, Belgium c AB-InBev SA/NV, Brouwerijplein 1, B-3000 Leuven, Belgium d Centre for Food and Microbial Technology, Department of Microbial and Molecular Systems (M2S), LFoRCe, KU Leuven, Kasteelpark Arenberg 33, 3001 Leuven, Belgium article info abstract Article history: Ever since the introduction of controlled fermentation processes, alcoholic fermentations and Saccharomyces Received 24 November 2014 cerevisiae starter cultures proved to be a match made in heaven. The ability of S. cerevisiae to produce and with- Received in revised form 23 March 2015 stand high ethanol concentrations, its pleasant flavour profile and the absence of health-threatening toxin Accepted 3 April 2015 production are only a few of the features that make it the ideal alcoholic fermentation organism. However, in cer- Available online 8 April 2015 tain conditions or for certain specific fermentation processes, the physiological boundaries of this species limit its Keywords: applicability. Therefore, there is currently a strong interest in non-Saccharomyces (or non-conventional) yeasts fi β-Glycosidase with peculiar features able to replace or accompany S. cerevisiae in speci c industrial fermentations. Viable but nonculturable (VBNC) Brettanomyces (teleomorph: Dekkera), with Brettanomyces bruxellensis as the most commonly encountered rep- Custers effect resentative, is such a yeast. Whilst currently mainly considered a spoilage organism responsible for off-flavour Bioethanol production in wine, cider or dairy products, an increasing number of authors report that in some cases, these Lambic yeasts can add beneficial (or at least interesting) aromas that increase the flavour complexity of fermented Brettanomyces anomala beverages, such as specialty beers. Moreover, its intriguing physiology, with its exceptional stress tolerance and peculiar carbon- and nitrogen metabolism, holds great potential for the production of bioethanol in continuous fermentors. This review summarizes the most notable metabolic features of Brettanomyces, briefly highlights recent insights in its genetic and genomic characteristics and discusses its applications in industrial fermentation processes, such as the production of beer, wine and bioethanol. © 2015 Published by Elsevier B.V. Contents 1. Introduction...............................................................25 2. Taxonomy of Brettanomyces ........................................................25 3. The Brettanomyces genomeandphenome..................................................26 3.1. Genome of Brettanomyces .....................................................26 3.2. Phenome of Brettanomyces .....................................................27 3.2.1. Brettanomyces growthandfermentation...........................................27 3.2.2. Brettanomyces flavourproduction..............................................30 3.3. Microbial safety of Brettanomyces ..................................................32 3.3.1. Biogenicamineproduction.................................................32 3.3.2. Cycloheximideresistance..................................................33 4. Brettanomyces inindustrialfermentationprocesses.............................................33 4.1. Spontaneouslyfermentedbeer...................................................33 4.2. Wine...............................................................33 4.3. Bioethanol............................................................34 ⁎ Corresponding author at: KU Leuven CMPG — Genetics and Genomics/VIB Laboratory of Systems Biology, Bio-Incubator, Gaston Geenslaan 1, 3001 Leuven, Belgium. Tel.: +32 16 751393; fax: +32 16 751391. E-mail address: [email protected] (K.J. Verstrepen). http://dx.doi.org/10.1016/j.ijfoodmicro.2015.04.005 0168-1605/© 2015 Published by Elsevier B.V. J. Steensels et al. / International Journal of Food Microbiology 206 (2015) 24–38 25 5. Concludingremarksandfutureperspectives................................................ 34 Acknowledgements.............................................................. 34 References.................................................................. 34 1. Introduction In this review, we provide a comprehensive overview of the cur- rently available information on Brettanomyces yeasts. In the first sec- Since early Neolithic times, humans relied on fermentation process- tion, the biological and genetic diversity and the taxonomy of the es to introduce desirable flavours and increase the shelf life and safety of Brettanomyces genus are addressed. In a second part, the genetic fea- foods and beverages (Chambers and Pretorius, 2010; Sicard and tures of B. bruxellensis, and how evolution shaped the genome of this Legras, 2011). Whilst initially conducted spontaneously, most mod- species, are reviewed. Next, we review the phenotypic characteristics, ern fermentation processes are initiated and managed by a well- such as production of flavour-active compounds, growth patterns in in- defined, single-strain starter cultures (Barnett and Lichtenthaler, dustrially relevant conditions and aspects of microbial safety. In the last 2001; Steensels and Verstrepen, 2014). In alcoholic fermentations, part,wediscusstheroleandpotentialofBrettanomyces in three fermen- these starter cultures most commonly consist of a strain belonging tation processes, namely the production of spontaneously fermented to Saccharomyces cerevisiae, or one of its close relatives. beers, wines and bioethanol, and we discuss future perspectives. Howev- However, pure culture fermentations also have disadvantages; er interesting, other aspects regarding Brettanomyces fall outside the selecting one single strain with all beneficial characteristics neces- scope of this review and are only mentioned briefly, but are reviewed sary for an efficient and high-quality fermentation might prove diffi- in detail elsewhere. These topics include Brettanomyces detection, identi- cult, since the diversity of wild, contaminating yeasts and bacterial fication and enumeration (Barata et al., 2012; Fugelsang and Edwards, species creates a distinct fermentation and flavour profile and a lot 2007; Wedral et al., 2010), genomic evolution (Curtin and Pretorius, of the complexity or subtle aromatic notes might be eliminated in 2014) and genetic modification methods (Schifferdecker et al., 2014). pure culture fermentations. Despite that several strain improvement methods are described to enrich the aromatic profile or fermentation 2. Taxonomy of Brettanomyces efficiency of S. cerevisiae strains (Steensels et al., 2014a,b), these techniques also have their limitations, and non-Saccharomyces (or The etymological origin of the Brettanomyces yeast genus lies in non-conventional) yeasts are becoming increasingly popular in the Great Britain, where it was first isolated by Claussen in 1904 (see also fermentation industry (Ciani and Comitini, 2011; Cordero-Bueso above). Whilst Claussen did call his isolate “Brettanomyces” (deducted et al., 2013; Gonzalez et al., 2013; Johnson, 2013). Whilst many of from the Greek words Brettano [British brewer] and Myces [fungus]), these yeasts are still stigmatized as unwanted spoilage organisms, he initially classified it as a Torula species. However, in 1921, Kufferath some of them can have a beneficial role by increasing the fermenta- and Van Laer isolated a yeast strain from Belgian lambic beers with tion efficiency, lowering the spoilage risk or changing the flavour the same characteristics described by Claussen and classified it as profile of the end product (Steensels and Verstrepen, 2014). One of Brettanomyces bruxellensis (Custers, 1940). The first systematic investi- such microbes is Brettanomyces. This yeast was originally described gation of Brettanomyces yeasts was conducted and reported by Mathieu in 1904 by Niels Hjelte Claussen, a younger colleague of the famous Custers in 1940, who characterized 17 different strains, isolated from Emile Christian Hansen, at the Carlsberg brewery. Claussen isolated English and Belgian beers. this peculiar yeast from beer, where it was held responsible for Since its first description, the taxonomy of Brettanomyces has been performing the secondary fermentation and development of charac- the subject of debate and there have been many reclassifications over teristic flavours of the finest English stock ales (Claussen, 1904). In- the years. Initially, the classification was solely based on a few, asexually terestingly, this initial isolation of Brettanomyces resulted in the reproducing (anamorphic) variants (Custers, 1940). However, a few de- first patented microorganism in history (UK patent GB190328184). cades later (in 1960), the formation of ascospores was observed in some In the claims of the patent, Claussen targets “the employment in strains and the genus Dekkera was introduced in the taxonomy as the the