EFFECT OF DAS, ZEA AND OTA MYCOTOXINS ON THE FERMENTATION ACTIVITY OF BREWING YEAST

Barbara Foszczyńska, Ewelina Dziuba, Joanna Chmielewska, Joanna Kawa-Rygielska
Department of Food Storage and Technology, Wrocław University of Environmental and Life Sciences, Poland

ABSTRACT

The research was aimed at determining the influence of DAS, ZEA and OTA mycotoxins on the course of malt wort fermentation with selected strains of brewing yeast. The following concentrations of mycotoxins in wort were used: 5 and 15 µg·ml^-1 (DAS), 5 and 50 µg·ml^-1 (ZEA), and 15 µg·ml^-1 (OTA). Contaminated worts were subjected to the fermentation process at 10-12°C for 9 days (Saccharomyces carlsbergensis I-S.ca./13 and Saccharomyces cerevisiae (lager) 23) as well as at 23-25°C for 5 days (Saccharomyces cerevisiae I-S.c./46 and Saccharomyces cerevisie I-S.c./57). Analyses involved, among other things, dynamics of fermentation, utilization of carbohydrate components, a degree of attenuation and mycotoxin remaining. The study demonstrated that mycotoxins exerted various influence on the course and results of malt wort fermentation. The highest toxicity was observed for DAS which at a concentration of 15 µg·ml^-1 inhibited the utilization of wort extract components. Zearalenone affected negatively the fermentation process already at a dose of 50 µg·ml^-1. Ochratoxin A applied at a concentration of 15 µg·ml^-1 was found not to affect yeast metabolism. The brewing yeast were characterized by diversified fermentation activity in the medium contaminated with mycotoxins. The highest sensitivity to toxins was observed in the case of S.carlsbergensis I-S.ca./13 and S.cerevisiae I-S.c./46 yeast.

Key words: diacetoxyscirpenol, zearalenone, ochratoxin A, brewing yeast, fermentation.

INTRODUCTION

Care over a high quality of brewing raw materials and a proper course of the malting process and beer production coupled with high production hygiene ensure obtaining a safe product with values acceptable by a consumer. Still, in practice the quality of raw materials used in the production of beer is far from expected, also in the aspect of risks of microbiological origin. This has been confirmed by an increasing number of published data on the level of beer contamination with secondary metabolites of filamentous fungi. For instance, beers have been found to contain aflatoxins, ochratoxin A (OTA), fumonisins and Fusarium toxins: deoxynivalenol (DON), diacetoxyscirpenol (DAS), T-2 toxin, and zearalenone (ZEA) [14,20,22]. In European beers, DON has been most often detected toxin.

An overview of literature indicates that in the brewing process the level of mycotoxins is subject to a reduction. It occurs, among others, during mashing, boiling and fermentation of wort [2,8,17]. Some toxins, including DON, T-2, ZEA and aflatoxins, display resistance to high temperature [15,26,27]. Those metabolites, once introduced into a technological process together with the basic raw material – especially the non-malted one, are likely to penetrate into a wort, thus posing risk to the fermentation process.

In the last years a number of investigations have been undertaken to evaluate interactions between a toxin and a yeast cell. In many of them attention was paid to the determination of the effect of toxins on the yeast growth. It has been demonstrated, among others, that mycotoxins exert an unfavorable influence on proliferation and viability of cells [3-5]. Their effects are determined by a variety of factors, e.g. type and concentration of toxins, yeast strain, conditions of incubation (temperature, time, inoculum concentration), a source of carbon and presence of other toxic compounds, e.g. ethanol [6,23,24]. While the effect of toxins on the growth of yeast is being investigated in detail at present, data are lacking on the behavior of yeasts during fermentation of contaminated wort. Therefore, the reported study was aimed at determining the influence of various concentrations of DAS, ZEA and OTA mycotoxins on the course and results of malt wort fermentation as well as at investigating the sensitivity of selected strains of brewing yeast to the contaminating factors. An additional objective of the study was to determine quantitative changes of mycotoxins during wort fermentation.

MATERIAL AND METHODS

Experimental material
The experimental material were the following toxins: diacetoxyscirpenol (DAS), zearalenone (ZEA) and ochratoxin A (OTA), purchased in Sigma Aldrich Ltd.

The biological material included four strains of brewing yeast: Saccharomyces carlsbergensis I-S.ca./13, Saccharomyces cerevisiae (lager) 23, Saccharomyces cerevisiae I-S.c./46 and Saccharomyces cerevisiae I-S.c./57. In the next part of this paper the abbreviations for names of the yeast strains were used, respectively: S.ca. 13; S.c. 23; S.c. 46 and S.c. 57. The S.ca. 13, S.c. 46 and S.c. 57 yeast originated from the culture collection of the Institute of Agricultural and Food Biotechnology in Warsaw. The strain S.c. 23 came from the dry brewing yeast Saflager S-23 (Fermentis Division of S.I.Lesaffre, France).

Fermentation medium was 12% wort obtained from Pilsner type malt. The wort was contaminated with a solution of mycotoxin in ethanol at the following concentrations: DAS – 5 and 15 µg·ml^-1; ZEA – 5 and 50 µg·ml^-1 as well as OTA – 15 µg·ml^-1. The selection of concentrations was based on results of screening cultures of the yeast strains on a synthetic medium with various doses of mycotoxins [10]. A control sample was wort without toxin, but with a volume of alcohol equivalent to that introduced with the toxin solution.

Fermentation samples
Control and contaminated worts were inoculated under sterile conditions with inoculum, thus reaching a concentration of 20x10⁶ cells·ml^-1. After inoculation, each type of wort was separated into a series of fermentation flasks (vol. of 100 ml). The process of fermentation with S.ca. 13 and S.c. 23 strains was carried out at a temperature of 10-12°C for 9 days, whereas that with S.c. 46 and 57 strains at a temperature of 23-25°C for 5 days.

During the fermentation process, samples were collected periodically for determinations of:

• pH

• dynamics of fermentation (expressed by the amount of CO₂ emitted in subsequent stages of fermentation in relation to its total amount released in the control sample, in %)

• extract content (with the refractometric method).

After fermentation, the worts were assayed for: the content of ethanol, the content of apparent extract and apparent degree of attenuation (Electronic Beer Analyzer DSA 48, laboratory of Namysłów brewery).

Before and after the fermentation process, the worts were analyzed for the contents of carbohydrates (glucose, fructose, maltose and maltotriose) and mycotoxins (DAS, ZEA and OTA) with the HPLC method.

Determination of carbohydrates content
Samples of wort (5 ml) were centrifuged on an EBA 21 centrifuge (10 000 rpm, 10 min.) and filtered using syringe filters with mesh diameter of 0.45 µm. Purified samples were supplied to an autosampler of a liquid chromatograph PRO-STAR Varian with a Supelcogel C-610H column (30 cm x 7.8 mm ID); eluent – 0.1% orthophosphoric acid, separation temperature – 50°C, flow rate – 0.5 ml·min^-1; and RI detector.

Determination of DAS content
Samples of both stock and attenuated wort were filtered (microfilters with mesh diameter of 4 µm). Clear wort was injected onto a column of Waters 501 apparatus. Determinations were conducted at the following parameters: a C₁₈ Nova Pak Waters column (3.9x300 mm); mobile phase – acetonitrile : water (45 : 55 v/v); flow rate – 0.4 ml·min^-1; an absorption detector Waters 496 (λ=195 nm); and retention time – 10.0 min.

Determination of ZEA content
Portions of 0.5 ml of samples with ZEA concentration of 5 µg·ml^-1 or 0.05 ml portions of samples with ZEA concentration of 50 µg·ml^-1 were measured out for analyses. The samples were evaporated until dry in a stream of nitrogen, the dry residue was dissolved in 5 ml of a mixture water : methanol : acetonitrile (70 : 20 : 10 v/v/v) and filtered. The content of toxins was determined using: a Waters 2695 Separations Module apparatus; a C₁₈ Nova Pak Waters column (3.9x300 mm); mobile phase – acetonitrile : water : methanol (46:46:8 v/v/v), flow rate – 0.6 ml·min^-1; Waters 2475 Multi λ Fluorescence Detector (at excitation wavelength of 274 nm and emission wavelength of 440 nm), Waters 2996 Photodiode Array Detector (λ 235 nm), and retention time – 16 min.

Determination of OTA content
For analyses, 0.135 ml portions of samples were measured out and evaporated in a stream of nitrogen. The dry residue was dissolved in 5 ml of methanol. The precipitate obtained was dissolved using ultrasounds. The sample was injected onto a column of the HPLC apparatus. Use was made of: a Waters 501 apparatus; a C₁₈ Nova Pak Waters column (3.9x300 mm), mobile phase – water : acetonitrile : acetic acid (99 : 99: 2 v/v/v); flow rate – 0.6 ml·min^-1; a fluorescent detector Waters 420 (at excitation wavelength of 365 nm and emission wavelength of 420 nm), and retention time – 12.1 min.

The HPLC analyses were carried out with standards of particular mycotoxins with an initial concentration of 100 µg·ml^-1.

RESULTS

Fermentation of the wort samples contaminated with mycotoxins demonstrated that the course and final results of the process depended on the type of toxin, its concentration and yeast strain applied.

The greatest impact on the fermentation process was exerted by diacetoxyscirpenol (DAS), which was observed based on changes in pH, the volume of CO₂ emitted and a degree of utilization of carbohydrate components.

The DAS toxin was found to inhibit the ability of yeast to acidify the fermentation medium. It referred especially to strains S.ca. 13 and S.c. 46 fermenting the wort contaminated with the highest dose of DAS, i.e. 15 µg·ml^-1 (Fig. 1). In the presence of DAS yeast were characterized by weaker dynamics of fermentation along with an increasing concentration of the toxin (Fig. 2). At the highest concentration of DAS, the S.ca. 13 yeast generally did not undertake wort fermentation. The S.c. 46 strain was also sensitive to DAS toxin, yet after noticeably poorer initial stage of fermentation, it intensified the process and, consequently, the amount of emitted CO₂ reached 80-100% of that released in the control sample. Similar disturbances, however considerably less intensive, were observed for the strain S.c. 57. The least serious consequences of contamination with DAS toxin occurred in the samples fermented with S.c. 23, over the entire process the dynamics of fermentation was comparable to that of the control sample.

Fig. 1. The effect of DAS toxin on pH changes during fermentation of malt wort

Fig. 2. The effect of DAS toxin on dynamics of malt wort fermentation (expressed by the amount of CO2 emitted in subsequent stages of fermentation in relation to its total amount released in the control sample, in %)

So diversified course of the fermentation dynamics was confirmed by the capability of strains for utilization of the extract compounds (Fig. 3). The worst rate of extract components assimilation occurred in the samples contaminated with DAS toxin at a level of 15 µg·ml^-1, and then subjected to the fermentation process with the strains S.ca. 13 and S.c. 46. Initially, the S.c. 46 strain poorly utilized the wort extract, however in the middle of the process there occurred an acceleration and the yeast appeared to utilize all available monosaccharides and maltose (except for samples with the addition of 15 µgDAS·ml^-1 in which utilization of that disaccharide oscillated around 80%) (Fig. 4). In turn, in the DAS-containing medium the S.c. 13 strain utilized only glucose and fructose as well as ca. 50% of available maltose in the variant with the lowest dose of toxin (5 µg·ml^-1). Both the yeast strains did not assimilate maltotriose, which distinguished them from the two other strains. Maltotriose is utilized by brewing yeast mainly during beer maturation, hence worthy of noticing is a high activity of S.c. 23 and S.c. 57 strains which, irrespective of the contaminating agent, fermented almost the whole amount of that carbohydrate (S.ca. 13 – 95%; S.c. 57 – 84%). The attenuation degree of the samples confirms these observations (Table 1). The degree of apparent attenuation of the control worts and worts contaminated with DAS was high and reached 77-79%. Apparent attenuation of the samples by S.c. 13 and 46 yeast reached a level of 66% and was observed to decrease along with an increase in DAS concentration.

Fig. 3. The effect of DAS toxin on extract content during fermentation of malt wort

Fig. 4. The effect of DAS toxin on utilization of glucose (GL), fructose (FR), maltose (MA) and maltotriose (MT) by brewing yeast

Table 1. The effect of DAS toxin on attenuation of malt worts

Yeast strain	DAS concentration [µg·ml-1]	Alkohol [% vol.]	Apparent extract [%]	Apparent degree of attenuation [%]
S.ca. 13	0 5 15	4.01 2.53 0	3.79 6.72 9.57	66.5 41.1 16.1
S.c. 23	0 5 15	4.75 4.82 4.77	2.36 2.36 2.35	79.1 79.3 79.2
S.c .46	0 5 15	4.03 4.17 3.79	3.83 3.89 4.71	66.4 66.7 60.0
S.c. 57	0 5 15	4.62 4.74 4.71	2.59 2.54 2.69	77.0 77.8 76.7

Contrary to DAS, zearalenone did not exert any significant effect on the course and results of fermentation of malt wort. In all variants of fermentation, differing in the concentration of toxins and yeast strain applied, the secretion of acidic compounds to the medium proceeded similarly as in the control samples (Fig. 5). An unbeneficial impact of zearalenone on the course of the fermentation process was observed only in the samples with the highest concentration of toxin, i.e. 50 µg·ml^-1, run by the strain S.ca. 13. Under those conditions, the S.ca. 13 yeast utilized extract components to a worse extent (Fig. 6), which has been confirmed by poored dynamics of fermentation (Fig. 7). Yet, at the end of the process the content of apparent extract in the wort as well as the amount of released CO₂ were comparable to those reported in the non-contaminated sample. During fermentation of wort with ZEA toxin the S.ca. 13 yeast, likewise the other strains, utilized the available pool of monosaccharides and maltose (Fig. 8) and additionally, though to a small extent, maltotriose (from 13.8 to 21%). Finally, ethanol content as well as a degree of apparent attenuation, did not differed fundamentally from the values obtained for the control sample (Table 2).

Fig. 5. The effect of ZEA toxin on pH changes during fermentation of malt wort

Fig. 6. The effect of ZEA toxin on dynamics of malt wort fermentation (expressed by the amount of CO2 emitted in subsequent stages of fermentation in relation to its total amount released in the control sample, in %)

Fig. 7. The effect of ZEA toxin on extract content during fermentation of malt wort

Fig. 8. The effect of ZEA toxin on utilization of glucose (GL), fructose (FR), maltose (MA) and maltotriose (MT) by brewing yeast

Table 2. The effect of ZEA toxin on attenuation of malt worts

Yeast strain	ZEA concentration [µg·ml-1]	Alkohol [% vol.]	Apparent extract [%]	Apparent degree of attenuation [%]
S.ca. 13	0 5 50	4.16 4.20 4.04	3.80 3.79 3.87	67.2 67.4 66.1
S.c. 23	0 5 50	5.11 4.79 5.02	2.37 2.37 2.39	80.2 79.1 79.7
S.c .46	0 5 50	4.48 4.30 4.35	3.89 3.88 3.90	68.2 67.4 67.6
S.c. 57	0 5 50	4.89 4.34 5.26	2.61 2.67 2.69	77.8 76.6 78.5

The examined yeast strains were characterized by a high resistance to the presence of ochratoxin A at a concentration of 15 µg·ml^-1. The toxin did not exert any effect on changes in wort pH, fermentation dynamics, utilization of carbohydrate components or productivity of ethanol (Fig. 9-12, Table 3).

Fig. 9. The effect of OTA toxin on pH changes during fermentation of malt wort

Fig. 10. The effect of OTA toxin on dynamics of malt wort fermentation (expressed by the amount of CO2 emitted in subsequent stages of fermentation in relation to its total amount released in the control sample, in %)

Fig. 11. The effect of OTA toxin on extract content during fermentation of malt wort

Fig. 12. The effect of OTA toxin on utilization of glucose (GL), fructose (FR), maltose (MA) and maltotriose (MT) by brewing yeast

Table 3. The effect of OTA toxin on attenuation of malt worts

Yeast strain	OTA concentration [µg·ml-1]	Alkohol [% vol.]	Apparent extract [%]	Apparent degree of attenuation [%]
S.ca. 13	0 15	4.12 4.43	3.73 3.72	67.4 68.9
S.c. 23	0 15	4.22 4.75	2.30 2.29	81.4 79.6
S.c .46	0 15	4.82 4.12	3.92 3.99	69.6 65.9
S.c. 57	0 15	5.10 4.65	2.67 2.74	78.1 76.1

Fig. 13. The remaining of DAS (a), ZEA (b) and OTA (c) toxins after fermentation of malt worts

Before and after fermentation process, the worts were determined for the content of mycotoxins. Results of mycotoxin remaining, expressed in % of the initial value, were demonstrated in Fig. 13. The highest degree of mycotoxin reduction occurred during the fermentation of wort contaminated with zearalenone (Fig.13b). The residue of ZEA was highly diversified depending on the concentration and yeast strain applied, yet it did not exceed 50%. The recovery of DAS in worts fluctuated between 52 and 92%, and that of OTA between 66 and 99% (Fig.13a and c). Usually, a higher degree of reduction of DAS and ZEA toxins was observed at their lower concentration in the wort. It was especially noticeable in the samples contaminated with ZEA. In that fermentation series, the best effects of ZEA reduction were obtained with the use of S.c. 23 strain. The ZEA remaining in wort, irrespective of the concentration, reached as little as 2% of the introduced amount. It should be emphasized that the S.c. 23 strain was characterized by the best fermentative activity. In turn, the S.c. 13 yeast, as compared to the other strains, reduced the amount of toxins in the wort to a smaller extent event at a low initial concentration of ZEA, i.e. 5 µg·ml^-1. A similar tendency was observed in the worts contaminated with DAS or OTA. The highest amount of those toxins remained after the fermentation with strains of S.ca. 13 and S.c. 23.

DISCUSSION

Fermentation of wort is one of the key stages of beer production. The course and results of fermentation are determined, to a large extent, by the composition of wort and quality of yeast applied, the latter being a sum of strain properties and physiological condition of the biomass used. Yeasts are extremely susceptible to changes in the environment. They respond to unfavorable conditions with stress which, in turn, results in their fermentation activity. In the case of yeast, the stress-inducing factors are compounds inhibiting the physiological status of cells, e.g. ethanol or CO₂ released during fermentation [18,21]. Such substances may also be mycotoxins contaminating the fermentation medium.

This paper presents results that described the fermentation activity of brewing yeast in the malt wort contaminated with various doses of mycotoxins DAS, ZEA and OTA. The study is a continuation of investigations, in which toxins were demonstrated to exert an inhibiting effect on the yeasts growth [10]. The next stage of investigations showed that mycotoxins affected the physiological condition of yeast during the fermentation process [11,12]. The strongest activity was observed for T-2 toxin and DAS, especially against S.ca. 13 and S.c. 46 yeast. The results obtained in the reported study confirm that reduced viability and vitality of yeast, especially at the begining of fermentation affected the capability of cells for utilizing wort components.

The effect of mycotoxins on the activity of yeast depended on the type and concentration of a contaminating factor. As compared to zearalenone and ochratoxin A, more significant in the process of biomass proliferation and fermentation was the presence of DAS which demonstrated the inhibiting strength similar to that of T-2 toxin [13]. Mycotoxins of the trichothecene group are classified into three categories based on the inhibiting effect on the growth of yeast: HT-2, T-2 triol, and T-2 tetraol characterized by a low toxicity, T-2 and DAS being medium toxic as well as verrucarine A and roridine A being the most toxic [25]. All these mycotoxins exert a negative influence on mitochondria. T-2 toxin inhibits mitochondrial function at the level of the electron transport chain [16]. In addition, the trichothecenes are responsible for the inhibition of protein synthesis in sphaeroplasts in S. cerevisiae [9].

The effect of DAS and DON on the growth and fermentation activity of S. cerevisiae yeast was investigated by Whitehead and Flannigan [29]. Diacetoxyscirpenol inhibited the growth of yeast and delayed the initiation of fermentation to a greater extent than related with it deoxynivalenol. It was observed that the production of ethanol from the medium with 10 µg DAS·ml^-1 was delayed, however after 150 hours the fermentation equaled the productivity of the control sample. It is likely to indicate adaptation of yeast to the presence of a toxic factor, which has also been observed in presented researches. A fine example of such a behavior was strain S.c. 57 which, after some disturbances at the initial stages of fermentation of DAS-contaminated wort, attenuated the extract to the level of the control sample. Similar attempts of adaptation have been observed in the case of strain S.c. 46, still the effects of fermentation were usually worse than in the non-contaminated sample. In turn, the S.c. 23 yeast even at the highest concentration of DAS utilized the available carbohydrate, thus yielding a high degree of attenuation. That strain appeared to be the least sensitive to various concentrations of the toxins applied, both during growth on the model medium [10] as well as during fermentation of malt wort [12].

The observed diversified response of the yeast strains to the toxins could have been linked with the structure and integrity of cellular membranes. It is known that species of yeast, and even strains of the same species, differ in the composition of cell membrane which affects its permeability. Perhaps, the low sensitive of the S.c. 23 strain to DAS toxin results from low permeability of membranes, since the wort after fermentation was found to contain the highest amount of DAS toxin residues (92%). In turn, that strain was characterized by the highest degree of zearalenone reduction, which indicates its capability for transforming toxins into other, less toxic forms. Zearalenone can be transformed by various species of yeasts into two isomers: alpha-zearalenol and beta-zearalenol [1,7]. The latter is generally less estrogenic and its production may be considered as a partial detoxication of ZEA. Matsuura and Yoshizawa [19] claim that many strains of S. cerevisiae are able to easily transform ZEA into beta-zearalenol in 95%.

Biotransformation of zearalenone has been best recognized so far. Results obtained indicated, however, that various species of yeast may reduce also other mycotoxins. For example, within 10 days Rhodotorula glutinis yeast reduced the amount of DON and ZEA in the maize fodder by 85 and 93%, respectively [1]. The T-2 toxin may be transformed to compounds with trace toxicity: HT-2 and T-2 triol [29], whereas ochratoxin A to α-ochratoxin A not displaying toxic properties [28]. Results of OTA remaining in worts point to its partial conversion by the most active strains, i.e. S.c. 23 and S.c. 57 (recovery at a level of 60-70%). Certainly, that toxin could have been retained by yeast cells. Scott et al. [28] demonstrated that some OTA was taken up by the yeast, up to 21% depending on strain. Those authors emphasized that OTA was a stable compound that could be retained after the fermentation process in a relatively high amount (ca. 85%). Results of our study, especially those referring to more susceptible strains, confirm that observation.

CONCLUSIONS

Summarizing results reported in this paper it should be concluded that mycotoxins exerted various influence on the course and results of wort fermentation. The most toxic appeared to be DAS which, especially at the highest concentration (15 µg·ml^-1), inhibited the utilization of extract components (mainly through the strain S.ca. 13), thus deteriorating the final effects of the fermentation process. Zearalenone was found to affect negatively the process of fermentation already at a dose of 50 µg·ml^-1, yet it depended on the yeast strain applied. In turn, ochratoxin A used at a concentration of 15 µg·ml^-1 was observed not to affect yeast metabolism.

The examined strains of brewing yeast were characterized by diversified fermentation activity both in the non-contaminated medium and that contaminated with mycotoxins. The best activity was reported for S.c. 23 yeasts, which under conditions of bottom fermentation, effectively utilized sugars (including maltotriose) providing a high degree of apparent attenuation. They appeared to be resistant even to the such strong toxin as DAS. In addition, they demonstrated the highest capacity for reducing ZEA level in the wort. A similar fermentation activity, yet slightly higher sensitivity to toxins, was shown for the strain S.c. 57 which after some disturbances in the first stage of fermentation of DAS-contaminated worts finally reached results approximating those reported for the uncontaminated samples. The highest sensitivity to toxins was demonstrated for the yeasts S.ca. 13 and S.c. 46, however the latter made attempts to adapt to unfavorable conditions of the contaminated wort.

REFERENCES

1. Bacutis B., Baliukoniene V., Paskevicius A., 2005. Use of biological method for detoxification of mycotoxins, Botanica Lithuanica, Suppl. 7, 123-129.

2. Baxter E.D., Slaiding I.R., Kelly B., 2001. Behavior of ochratoxin A in brewing. J. Am. Soc. Brew. Chem. 59(3), 98-100.

3. Boiera L.S., Bryce J.H., Steward G.G., Flanningan B., 1999. Inhibitory effect of Fusarium mycotoxins on growth of brewing yeasts. 1. Zearalenone and fumonisin B₁, J. Inst. Brew. 105(6), 366-375.

4. Boiera L.S., Bryce J.H., Steward G.G., Flanningan B., 1999. Inhibitory effect of Fusarium mycotoxins on growth of brewing yeasts. 2. Deoxynivalenol and nivalenol, J. Inst. Brew. 105(6), 376-383.

5. Boeira L.S., Bryce J.H., Stewart G.G., Flannigan B., 2000. The effect of combinations of Fusarium mycotoxins (deoxynivalenol, zearalenone and fumonisin B₁) on growth of brewing yeasts. J. Appl. Microbiol. 88, 388-403.

6. Boiera L. S., Bryce J. H., Stewart G. G., Flanningan B., 2002. Influence of cultural conditions on sensitivity of brewing yeast growth to Fusarium mycotoxins zearalenone, deoxynivalenol and fumosin B₁. Internat. Biodeterivation & Biodegradation 50, 69-81.

7. Böswald C., Engelhardt G., Vogel H., Wallnofer P.R., 1995. Metabolism of the Fusarium mycotoxins zearalenone and deoksynivalenol by yeast strains of technological relevance, Nat. Toxins 3, 138-144.

8. Chu F.S., Chang C.C., Ashoor S.H., Prentice N., 1974. Stability of aflatoxin B₁ and ochratoxin A in brewing, Appl. Microbiol. 29(3), 313-316.

9. Cundliffe E., Cannon M., Davies J., 1974. Mechanism of inhibition of eukaryotic protein synthesis by trichothecene fungal toxins, Proc. Nat. Acad. Sci. USA 71(1), 30-34.

10. Dziuba E., Foszczyńska B., Stempniewicz R., 2007. Effect of mycotoxins DAS, ZEA and OTA on the growth of brewing yeast, Pol. J. Food Nutr. Sci. 57, 4(A), 123-129.

11. Foszczyńska B., Dziuba E., 2007. Stan fizjologiczny drożdży piwowarskich w czasie fermentacji brzeczek skażonych mykotoksynami. Cz.1: T-2 i ZEA [Physiological status of brewing yeasts during fermentation of worts contaminated with mycotoxins. P.1: T-2 and ZEA]. Acta Sci. Pol. Biotechnologia 6(1), 3-12 [in Polish].

12. Foszczyńska B., Dziuba E., 2007. Stan fizjologiczny drożdży piwowarskich w czasie fermentacji brzeczek skażonych mykotoksynami. Cz.2: DAS i OTA [Physiological status of brewing yeasts during fermentation of worts contaminated with mycotoxins. P.2: DAS and OTA]. Acta Sci. Pol. Biotechnologia 6 (2), 25-34 [in Polish].

13. Foszczyńska B., Dziuba E., Kawa-Rygielska J., Chmielewska J., Wojtatowicz M., 2006. Characteristics of selected features of brewing yeasts in environments containing T-2 toxin. EJPAU 9(1), #07, http://www.ejpau.media.pl/volume9/issue1/art-07.html.

14. Gumus T., Arici M., Demirci M., 2004. A survey of barley, malt and beer contamination with ochratoxin A in Turkey. J. Inst. Brew. 110(2), 146-149.

15. Kluczek J.P., Kojder., 2000. Mikotoksyny w zarysie [Mycotoxins in outline]. Wyd. Akad. Techn.-Roln., Bydgoszcz, 120-143 [in Polish].

16. Koshinsky H., Honour S., Khachatourians G., 1988. T-2 toxin inhibits mitochondrial function in yeast, Biochem. Biophys. Res. Commun. 151, 2, 809-814.

17. Krogh P., Hald B., Gjertsen P., Myken F., 1974. Fate of ochratoxin A and citrinin during malting and brewing experiments, Appl. Microbiol. 28(1), 31-34.

18. Majara M., O’Connor-Cox E.S.C., Axcell B.C., 1996. Trehalose – a stress protectant and stress indicator compoud for yeast exposed to adverse conditions, J. Am. Soc. Brew. Chem. 54(4), 221-227.

19. Matsuura Y., Yoshizawa T., 1985. Shokuhin Eiseigaku Zasshi, 26, 24 (cyt. za Boiera L.S., Bryce J.H., Steward G.G., Flanningan B., J. Inst. Brew., 1999, 105(6), 366-375).

20. Mbugua S.K., Gathumbi J.K., 2004. The contamination of Kenyan lager beers with Fusarium mycotoxins, J. Inst. Brew. 110(3), 227-229.

21. Odumeru J., D’Amore T., Russell I., Stewart G.G., 1992. Effects of heat shock and ethanol stress on the viability of a Saccharomyces uvarum (carlsbergensis) brewing yeast strain during fermentation of high gravity wort, J. Indust. Microb. Biotechnol. 10(2), 111-116.

22. Perkowski J., 2000. Mikotoksyny w surowcach piwowarskich i w piwie oraz w czasie jego otrzymywania [The occurrence of mycotoxins in malting, brewing and beer]. Przem. Ferm. Owoc.-Warz. 11, 14-16 [in Polish].

23. Schappert K.T., Khachatourians G.G., 1983. Effects of fusariotoxin T-2 on Saccharomyces cerevisiae and Saccharomyces carlsbergensis. Appl. Environ. Microbiol. 45(3), 862-867.

24. Schappert K.T., Khachatourians G.G., 1984. Influence of the membrane on T-2 toxin toxicity in Saccharomyces spp. Appl. Environ. Microbiol. 47(4), 681-684.

25. Schappert K.T., Koshinsky H.A., Khachatourians G.G., 1986. Growth inhibition of yeast by T-2, HT-2, T-2 triol, T-2 tetraol, diacetoxiscirpenol, verrucarol, verrucarin A, and roridin A mycotoxins. J. Am. Coll. Toxicol 5, 181-186.

26. Schwarz P.B., Casper H.H., Beattie S., 1995. Fate and development of naturally occurring Fusarium mycotoxins during malting and brewing, J. Am. Soc. Brew. Chem. 53(3), 121-127.

27. Scott P.M., 1984. Effects of food processing on mycotoxins, J. Food Prot. 47(6), 489-499.

28. Scott P. M., Kanhere S.R., Lawrence G.A., Daley E.F., Farber J.M., 1995. Fermentation of wort containing added ochratoxin A and fumonisins B₁ and B₂, Food. Addit. Contam. 12(1), 31-40.

29. Whitehead M. P., Flanningan B., 1989. The Fusarium mycotoxin deoxynivalenol and yeast growth and fermentation, J. Inst. Brew. 95, 411-413.

 

The study was carried out under a research project No. 2 P06T 020 28 financed by the State Committee for Scientific Research in the years 2005-2007.

 

Accepted for print: 17.12.2007

---

Barbara Foszczyńska
Department of Food Storage and Technology,
Wrocław University of Environmental and Life Sciences, Poland
Norwida 25, 50-375 Wrocław, Poland
phone: (+ 48 71) 32-05-237
fax: (+ 48 71) 32-05-273
email: bfoszcz@wnoz.ar.wroc.pl

Ewelina Dziuba
Department of Food Storage and Technology,
Wrocław University of Environmental and Life Sciences, Poland
Norwida 25, 50-375 Wrocław, Poland

Joanna Chmielewska
Department of Food Storage and Technology,
Wrocław University of Environmental and Life Sciences, Poland
Norwida 25, 50-375 Wrocław, Poland

Joanna Kawa-Rygielska
Department of Food Storage and Technology,
Wrocław University of Environmental and Life Sciences, Poland
Norwida 25, 50-375 Wrocław, Poland

---

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.

---

Main  -  Issues  -  How to Submit  -  From the Publisher  -  Search  -  Subscription