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Keywords: brewers’ yeast, active sludge bacteria, anaerobic digestion, biogas potential, biopolymer, 3D printing
Published in RUNG: 01.08.2022; Views: 809; Downloads: 20
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Abstract: In the presented paper we have investigated how large quantities of excess yeast and periodical releases of waste ethanol influence the operation of the anaerobic treatment process in a UASB reactor. The process was tested in a pilot-scale reactor with a design organic load of 16.0 kg/m3/day of COD. Through various stages of the experiment, several possible scenarios were tested, excess yeast was added continuously with concentrations up to 3 vol. %, whereas waste ethanol was added in batches of up to 0.8 % of daily volume load several days a week. The intent was to test real conditions in the treatment process. The whole experiment lasted for 77 days, where the maximum organic load of 24.72 kg/m3/day was successfully achieved with no adverse effects on the efficiency of the reactor performance although it significantly surpassed the design load. The COD efficiency at maximum OLR was 83.1 %, whereas the average was 88.0 %. The average biogas production rate increased from 2,044 m3/m3/day to 4.927 m3/m3/day. The microbial community structure analysis showed significant shifts only in the archaeal community (25 – 30 %) as a good adaptation to the addition of substrates. Monitoring the model brewery in applying the addition of yeast and ethanol to the wastewater treatment showed a 110 % increase in biomethane production. The consequence of the increased biomethane production is that the natural gas substitute ratio could be increased from the current average of 10.7 % to potentially 20.1 %, which is a substantial step towards the goal of renewable energy use.
Keywords: anaerobic digestion, biogas, brewery yeast, renewable energy, waste ethanol
Published in RUNG: 10.06.2021; Views: 1745; Downloads: 8
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Keywords: yeast, biofungicide, viticulture, Pinot Noir
Published in RUNG: 22.01.2020; Views: 2485; Downloads: 0
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Keywords: yeast, HCDC activity, wine colour, Pinot Noir, pyranoanthocyanins
Published in RUNG: 27.05.2019; Views: 2683; Downloads: 0
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Abstract: Conventionally, alcoholic fermentation in the production of wine is performed by yeast species Saccharomyces cerevisiae. There are numerous starters available, however due to the growing demand for wines with specific characteristics, other Saccharomyces and non-Saccharomyces species are being investigated for potential use as starters. [1]. Yeast selection has involved the development of techniques for detecting strains that might improve wines in terms of aroma, structure, colour and other technological properties [2]. Colour of the wine can be affected as some metabolites produced by yeast during fermentation may react with grape anthocyanins to produce highly stable pyranoanthocyanins. For the facilitation of formation of vinylphenolic pyranoanthocyanins, yeast strains with high hydroxycinnamate decarboxylase activity are used (HCDC). The mechanism of reaction is decarboxylation of hydroxycinnamic acids and formation of vinylphenols that condense with grape anthocyanins and form stabile vinyphenolic pyranoanthocyanin adducts [3]. It has been demonstrated that some non-Saccharomyces strains (Pichia guillermondii, Schizosaccharomyces pombe) have positive HCDC activity and they can produce vinylphenolic pyranoanthocyanins in higher concentrations than S. cerevisiae. A simple way of determining whether the yeast strain has HCDC activity or not, is the use of fermentation media with the addition of hydroxycinnamic acids, such as p-coumaric acid. The degradation of p-coumaric acid and transformation into 4-vinylphenol (and possibly in 4-ethylphenol) can be checked by LC-DAD. Most of the published data has been done on smaller number of strains. The goal of our work was to develop simple method for the screening of Slovenian in-house yeast collection, comprising of native isolates that mostly originated from Vipava valley and Karst region, and therefore try to determine strains with high HCDC activity. These strains can be used for wine fermentations in order to produce more stable pyranoanthocyanins; which is especially important in wines that has less anthocyanin concentration already from the grape, such as Pinot Noir. 103 different yeast strains belonging to 28 species were selected for the assessment of HCDC activity. In some cases the difference in p-coumaric acid metabolism rate between two strains exceeded 90%. All tested S. paradoxus strains showed higher than 40% degradation rate of p-coumaric acid. HCDC activity of S. cerevisiae strains which is the species most commonly used in fermentation, varied between 5.1 and 66.1%. The commercial strains tested, FPC and EC118 showed 43.9 and 21.5% conversion rate, respectively. It was observed that some native strains had higher HCDC activity than commercial tested ones. Three strains produced vinylphenol in concentration higher than 50 ppm, two of them being P. guillermondii and another strain being S. paradoxus (Sut85). In general strain with high HCDC activity also produced high concentration of 4-vinylphenol. The results showed that HCDC activity is highly strain dependent, which correlates with the literature data available. The proposed method is very simple and does not require special sample preparation prior to HPLC analysis. Furthermore, the proposed fermentations in deep-well microtiter plates allow the screening of high number of strains. The method could be used for routine screening, to determine which strain has high HCDC activity and produces high concentration of vinylphenols and can therefore be used in future for determination of strains ability to synthesize vinylphenolic pyranoanthocyanins.
Keywords: yeast, hydroxycinnamate decarboxylase, 4-vinylphenol
Published in RUNG: 18.06.2018; Views: 3369; Downloads: 0
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