Detection and characterisation of Fusarium hydrophobins inducing gushing in beer

Tuija Sarlin

Detection and characterisation of Fusarium hydrophobins inducing gushing in beer

Julkaisun otsikon käännös: Oluen ylikuohuntaa aiheuttavien Fusarium-hydrofobiinien osoittaminen ja karakterisointi

Tuija Sarlin

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Oluen ylikuohunta on ilmiö, jossa olut spontaanisti ja hallitsemattomasti vaahtoaa ulos pulloa avattaessa. Ylikuohunta jaetaan primääriin ja sekundääriin ylikuohuntaan. Sekundääriä ylikuohuntaa aiheuttavat erilaiset oluenvalmistuksen prosessitekniset ongelmat tai valmiin oluen virheellinen käsittely. Primäärin ylikuohunnan saavat aikaan homeiden tuottamat ylikuohuntatekijät, joita saattaa esiintyä maltaassa tai muissa oluen viljapohjaisissa raaka-aineissa. Yleisimmin primääriä ylikuohuntaa aiheuttavat Fusarium-homeet. Homeiden tuottamia ylikuohuntatekijöitä on tutkittu vuosikymmenien ajan, mutta niitä ei ole onnistuttu tarkasti identifioimaan. Tämän tutkimuksen hypoteesina oli, että pienet pinta-aktiiviset homeproteiinit, hydrofobiinit, ovat oluen primääriä ylikuohuntaa aiheuttavia ylikuohuntatekijöitä. Hydrofobiineilla on tunnetusti useita merkittäviä tehtäviä homeiden kasvussa ja kehityksessä. Tutkimuksen tavoitteena oli eristää ja karakterisoida hydrofobiineja ylikuohuntaa aiheuttavista homeista, etenkin Fusarium-suvun lajeista, sekä osoittaa, että nämä hydrofobiinit aiheuttavat oluen ylikuohuntaa. Lisäksi tavoitteena oli kehittää luotettava ja teollisuuden laadunvalvontaan soveltuva menetelmä ylikuohuntataipumuksen määrittämiseksi ohrasta ja maltaasta. Tutkimuksen tarkoituksena oli hankkia tietoa hydrofobiinien käyttäytymisestä ja kulkeutumisesta "ohrasta olueksi" -tuotantoketjussa. Peltokokeet osoittivat, että myös Suomen oloissa Fusarium-homeet kykenivät lisääntymään haitallisesti, mikä heikensi ohran ja siitä valmistetun maltaan laatua. Etenkin ylikuohuntataipumus lisääntyi. Tutkimuksessa havaittiin eroja siinä, miten haitallisesti eri Fusarium-lajit vaikuttivat laatuparametreihin; F. graminearum heikensi laatua voimakkaammin kuin F. culmorum ja etenkin F. poae. Tutkimus osoitti, että hydrofobiinit saavat aikaan ylikuohuntaa olueen lisättyinä. Fusarium-, Nigrospora- ja Trichoderma-suvun homeista eristetyt hydrofobiinit aiheuttivat oluen ylikuohuntaa jo hyvin pieninä pitoisuuksina (<1 ppm). Eristettyjen hydrofobiinien ylikuohunta-aktiivisuudet erosivat toisistaan todennäköisesti rakenne-erojen seurauksena. Käytimme tunnettujen hydrofobiinien aminohapposekvensseistä luomiamme todennäköisyysmalleja (profile HMMs) etsiessämme hydrofobiinien kaltaisia aminohapposekvenssejä Fusarium graminearum -homeen julkisesta genomitietopankista. Löysimme viisi hydrofobiinikandidaattia, joista valitsimme yhden todennäköisimmän jatkotutkimuksiin. Eristimme ja karakterisoimme tätä hydrofobiinia vastaavat geenit F. graminearum -kannan lisäksi F. culmorum- ja F. poae -kannoista. Eristetyt F. graminearum- ja F. poae -hydrofobiinigeenit siirrettiin Trichoderma reesei -tuottokantaan. Tuoteut ja puhdistetut proteiinit tunnistettiin hydrofobiineiksi ja nimettiin GzHYD5 (F. graminearum) ja FpHYD5 (F. poae). Molemmat hydrofobiinit aiheuttivat oluen ylikuohuntaa pitoisuutena 0,003 ppm. Hydrofobiinivasta-aineisiin perustuva immunologinen ELISA-testi kehitettiin hydrofobiinitasojen määrittämiseen ohra- ja mallasnäytteistä. Testin tulosten todettiin indikoivan maltaan ylikuohuntataipumusta. Testin avulla tutkittiin hydrofobiinitasoja "ohrasta olueksi" -tuotantoketjussa. Fusarium-homeiden todettiin tuottavan hydrofobiineja ohraan kasvukauden aikana pellolla sekä mallastuksessa, etenkin liotuksen ja idätyksen aikana. Pieni osa maltaan sisältämistä hydrofobiineista kulkeutui oluenvalmistusprosessin läpi päätyen valmiiseen olueen. Lisäämällä mallastuksen luontaiseen mikrobiyhteisöön kuuluvaa Pichia anomala VTT C-04565 -hiivaa ohran liotusveteen saatiin vähennettyä hydrofobiinien muodostumista mallastuksen aikana ja samalla valmiin maltaan ylikuohuntapotentiaalia.

Julkaisun otsikon käännös	Oluen ylikuohuntaa aiheuttavien Fusarium-hydrofobiinien osoittaminen ja karakterisointi
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Ohjaaja	Nordström, Katrina, Vastuuprofessori Haikara, Auli, Vastuuprofessori, Ulkoinen henkilö
Kustantaja	VTT Technical Research Centre of Finland
Painoksen ISBN	978-951-38-7473-5
Sähköinen ISBN	978-951-38-7474-2
Tila	Julkaistu - 2012
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-951-38-7474-2

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@phdthesis{ca7a2011e30d445e951c04d07d041d55,

title = "Detection and characterisation of Fusarium hydrophobins inducing gushing in beer",

abstract = "Gushing is a phenomenon in which beer spontaneously, without agitation, vigorously foams out from its container immediately on opening. Gushing has a marked negative effect on the overall image of beer. Numerous factors causing and contributing to gushing have been reported. Two types of gushing can be distinguished based on the origin of gushing-inducing substances. Non-malt related gushing, i.e. secondary gushing, is due to faults in the beer production process or to incorrect treatment of packaged beer. Primary gushing is induced by fungal metabolites, so-called gushing factors, which are present in malt or in other cereal raw materials of beer. Particularly species of the genus Fusarium have been linked to primary gushing. Although gushing factors produced by fungi have been studied for decades, none of them have hitherto been fully characterised. The hypothesis of this dissertation was that small fungal proteins called hydrophobins are one of the gushing factors inducing primary gushing. Hydrophobins are secreted, highly surface active, moderately hydrophobic proteins produced by filamentous fungi. Hydrophobins play key roles in the development and in the interactions of fungi with their environment and other organisms, particularly plants. The aim of this thesis was to isolate and characterise hydrophobins from gushing active fungi, especially from Fusarium species, and to demonstrate that these hydrophobins are able to induce gushing in beer. Currently, there is no practical, reliable and commercially available method for the prediction of beer gushing from large numbers of samples. The main goal of the work was to develop a test for detection of gushing potential of barley and malt by analysing the hydrophobin levels in samples. Moreover, the occurrence and fate of hydrophobins at different stages of the beer production chain were studied. This study revealed numerous effects of Fusarium fungi on the quality of barley grown under Finnish field conditions and of the corresponding malt. In particular, Fusarium infection increased the gushing potential of malt. The results of the study indicated that the extent of the impacts is species-dependent, F. graminearum having more severe detrimental effects on barley and malt quality than F. culmorum and particularly F. poae. We demonstrated that hydrophobins isolated from strains of the genera Fusarium, Nigrospora and Trichoderma induced beer gushing when added to bottled beer. Hydrophobin concentrations at the ppm level were sufficient for gushing induction. The gushing-inducing capabilities of the isolated hydrophobins varied probably due to their structural differences. We generated profile hidden Markov models for the different hydrophobin classes and searched the F. graminearum genome database for predicted proteins with these models. The search revealed five putative hydrophobin genes belonging to both the hydrophobin classes I and II. The best matching sequences and the corresponding genes were isolated from F. graminearum as well as from the related species F. culmorum and F. poae by PCR and were characterized by sequencing. One each of the putative F. graminearum and F. poae hydrophobin genes were expressed in the heterologous host Trichoderma reesei. The proteins corresponding to the genes were purified and identified as hydrophobins and named GzHYD5 and FpHYD5, respectively. Concentrations of 0.003 ppm of these hydrophobins were observed to induce vigorous beer gushing. An enzyme-linked immunosorbent assay (ELISA) was developed for determination of hydrophobin levels in barley and malt. A connection was found between the hydrophobin level and the gushing potential of malt, suggesting that the developed hydrophobin ELISA can be used for prediction of the gushing risk in malt. Fusarium fungi were observed to produce hydrophobins during the growing period of barley in the field as well as during the malting process, especially during the steeping and germination steps. A small portion of hydrophobins originating from Fusarium-infected malt was shown to pass through the brewing process, ending up in the final beer where they induced gushing when present in sufficiently high levels. Addition of a selected antagonistic starter culture, the yeast strain Pichia anomala VTT C-04565, into the steeping water of barley was shown to suppress hydrophobin production in malting, which in turn decreased the gushing potential of the corresponding malt.",

keywords = "gushing, hydrophobin, Fusarium, beer, malting, brewing, characterisation, detection, ELISA, gushing, hydrophobin, Fusarium, beer, malting, brewing, characterisation, detection, ELISA",

author = "Tuija Sarlin",

year = "2012",

language = "English",

isbn = "978-951-38-7473-5",

series = "VTT Science",

publisher = "VTT Technical Research Centre of Finland",

number = "13",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Detection and characterisation of Fusarium hydrophobins inducing gushing in beer

AU - Sarlin, Tuija

PY - 2012

Y1 - 2012

N2 - Gushing is a phenomenon in which beer spontaneously, without agitation, vigorously foams out from its container immediately on opening. Gushing has a marked negative effect on the overall image of beer. Numerous factors causing and contributing to gushing have been reported. Two types of gushing can be distinguished based on the origin of gushing-inducing substances. Non-malt related gushing, i.e. secondary gushing, is due to faults in the beer production process or to incorrect treatment of packaged beer. Primary gushing is induced by fungal metabolites, so-called gushing factors, which are present in malt or in other cereal raw materials of beer. Particularly species of the genus Fusarium have been linked to primary gushing. Although gushing factors produced by fungi have been studied for decades, none of them have hitherto been fully characterised. The hypothesis of this dissertation was that small fungal proteins called hydrophobins are one of the gushing factors inducing primary gushing. Hydrophobins are secreted, highly surface active, moderately hydrophobic proteins produced by filamentous fungi. Hydrophobins play key roles in the development and in the interactions of fungi with their environment and other organisms, particularly plants. The aim of this thesis was to isolate and characterise hydrophobins from gushing active fungi, especially from Fusarium species, and to demonstrate that these hydrophobins are able to induce gushing in beer. Currently, there is no practical, reliable and commercially available method for the prediction of beer gushing from large numbers of samples. The main goal of the work was to develop a test for detection of gushing potential of barley and malt by analysing the hydrophobin levels in samples. Moreover, the occurrence and fate of hydrophobins at different stages of the beer production chain were studied. This study revealed numerous effects of Fusarium fungi on the quality of barley grown under Finnish field conditions and of the corresponding malt. In particular, Fusarium infection increased the gushing potential of malt. The results of the study indicated that the extent of the impacts is species-dependent, F. graminearum having more severe detrimental effects on barley and malt quality than F. culmorum and particularly F. poae. We demonstrated that hydrophobins isolated from strains of the genera Fusarium, Nigrospora and Trichoderma induced beer gushing when added to bottled beer. Hydrophobin concentrations at the ppm level were sufficient for gushing induction. The gushing-inducing capabilities of the isolated hydrophobins varied probably due to their structural differences. We generated profile hidden Markov models for the different hydrophobin classes and searched the F. graminearum genome database for predicted proteins with these models. The search revealed five putative hydrophobin genes belonging to both the hydrophobin classes I and II. The best matching sequences and the corresponding genes were isolated from F. graminearum as well as from the related species F. culmorum and F. poae by PCR and were characterized by sequencing. One each of the putative F. graminearum and F. poae hydrophobin genes were expressed in the heterologous host Trichoderma reesei. The proteins corresponding to the genes were purified and identified as hydrophobins and named GzHYD5 and FpHYD5, respectively. Concentrations of 0.003 ppm of these hydrophobins were observed to induce vigorous beer gushing. An enzyme-linked immunosorbent assay (ELISA) was developed for determination of hydrophobin levels in barley and malt. A connection was found between the hydrophobin level and the gushing potential of malt, suggesting that the developed hydrophobin ELISA can be used for prediction of the gushing risk in malt. Fusarium fungi were observed to produce hydrophobins during the growing period of barley in the field as well as during the malting process, especially during the steeping and germination steps. A small portion of hydrophobins originating from Fusarium-infected malt was shown to pass through the brewing process, ending up in the final beer where they induced gushing when present in sufficiently high levels. Addition of a selected antagonistic starter culture, the yeast strain Pichia anomala VTT C-04565, into the steeping water of barley was shown to suppress hydrophobin production in malting, which in turn decreased the gushing potential of the corresponding malt.

AB - Gushing is a phenomenon in which beer spontaneously, without agitation, vigorously foams out from its container immediately on opening. Gushing has a marked negative effect on the overall image of beer. Numerous factors causing and contributing to gushing have been reported. Two types of gushing can be distinguished based on the origin of gushing-inducing substances. Non-malt related gushing, i.e. secondary gushing, is due to faults in the beer production process or to incorrect treatment of packaged beer. Primary gushing is induced by fungal metabolites, so-called gushing factors, which are present in malt or in other cereal raw materials of beer. Particularly species of the genus Fusarium have been linked to primary gushing. Although gushing factors produced by fungi have been studied for decades, none of them have hitherto been fully characterised. The hypothesis of this dissertation was that small fungal proteins called hydrophobins are one of the gushing factors inducing primary gushing. Hydrophobins are secreted, highly surface active, moderately hydrophobic proteins produced by filamentous fungi. Hydrophobins play key roles in the development and in the interactions of fungi with their environment and other organisms, particularly plants. The aim of this thesis was to isolate and characterise hydrophobins from gushing active fungi, especially from Fusarium species, and to demonstrate that these hydrophobins are able to induce gushing in beer. Currently, there is no practical, reliable and commercially available method for the prediction of beer gushing from large numbers of samples. The main goal of the work was to develop a test for detection of gushing potential of barley and malt by analysing the hydrophobin levels in samples. Moreover, the occurrence and fate of hydrophobins at different stages of the beer production chain were studied. This study revealed numerous effects of Fusarium fungi on the quality of barley grown under Finnish field conditions and of the corresponding malt. In particular, Fusarium infection increased the gushing potential of malt. The results of the study indicated that the extent of the impacts is species-dependent, F. graminearum having more severe detrimental effects on barley and malt quality than F. culmorum and particularly F. poae. We demonstrated that hydrophobins isolated from strains of the genera Fusarium, Nigrospora and Trichoderma induced beer gushing when added to bottled beer. Hydrophobin concentrations at the ppm level were sufficient for gushing induction. The gushing-inducing capabilities of the isolated hydrophobins varied probably due to their structural differences. We generated profile hidden Markov models for the different hydrophobin classes and searched the F. graminearum genome database for predicted proteins with these models. The search revealed five putative hydrophobin genes belonging to both the hydrophobin classes I and II. The best matching sequences and the corresponding genes were isolated from F. graminearum as well as from the related species F. culmorum and F. poae by PCR and were characterized by sequencing. One each of the putative F. graminearum and F. poae hydrophobin genes were expressed in the heterologous host Trichoderma reesei. The proteins corresponding to the genes were purified and identified as hydrophobins and named GzHYD5 and FpHYD5, respectively. Concentrations of 0.003 ppm of these hydrophobins were observed to induce vigorous beer gushing. An enzyme-linked immunosorbent assay (ELISA) was developed for determination of hydrophobin levels in barley and malt. A connection was found between the hydrophobin level and the gushing potential of malt, suggesting that the developed hydrophobin ELISA can be used for prediction of the gushing risk in malt. Fusarium fungi were observed to produce hydrophobins during the growing period of barley in the field as well as during the malting process, especially during the steeping and germination steps. A small portion of hydrophobins originating from Fusarium-infected malt was shown to pass through the brewing process, ending up in the final beer where they induced gushing when present in sufficiently high levels. Addition of a selected antagonistic starter culture, the yeast strain Pichia anomala VTT C-04565, into the steeping water of barley was shown to suppress hydrophobin production in malting, which in turn decreased the gushing potential of the corresponding malt.

KW - gushing

KW - hydrophobin

KW - Fusarium

KW - beer

KW - malting

KW - brewing

KW - characterisation

KW - detection

KW - ELISA

KW - gushing

KW - hydrophobin

KW - Fusarium

KW - beer

KW - malting

KW - brewing

KW - characterisation

KW - detection

KW - ELISA

M3 - Doctoral Thesis

SN - 978-951-38-7473-5

T3 - VTT Science

PB - VTT Technical Research Centre of Finland

ER -

Detection and characterisation of Fusarium hydrophobins inducing gushing in beer

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