K. Psarianos

University of Patras, Rhion, West Greece, Greece

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Publications (6)12.97 Total impact

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    ABSTRACT: A commercial culture of Kefir grew well at 30C and 37C with NaCl up to 4% (w/v) but at 42C and 4% (w/v) NaCl it grew very slowly. These conditions were selected for the mutation with N-methyl-N-nitrosoguanidine in order to improve cell yield at high temperatures and salt concentration. The mutated cells had higher biomass and growth rate compared with the original culture. The improvement of Kefir at high temperatures and salt concentrations offers advantages for uses in single cell protein production and alcohol production from whey containing high salt.
    No preview · Article · Mar 2002 · Biotechnology Letters
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    ABSTRACT: Low temperature wine making using freeze-dried gluten supported biocatalyst (FGB) is reported to be feasible. The biocatalyst was prepared by cell immobilization of the strain AXAZ-1 on gluten pellets followed by freeze drying. Batch fermentations were performed and the effects of initial Be density, temperature and total acidity of must on kinetic parameters were examined. Improved results were shown by freeze-dried immobilized cells on gluten as compared with free freeze-dried cells (ffdc). Fermentation times obtained at low temperatures (5–15 °C) could be accepted in industry. The total acidity of grape must does not affect the fermentation time while freeze-dried immobilized cells seem to have an operational stability from batch to batch. Amyl alcohols, the main volatile, are reduced by the decrease of the temperature below 20 °C. The percentages of amyl alcohols as a function of total volatiles were reduced and those of ethyl acetate were increased by the decrease of temperature, indicating improvements in quality and nutritional value.
    No preview · Article · Feb 2002 · Process Biochemistry
  • A Bekatorou · AA Koutinas · K Psarianos · M Kanellaki
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    ABSTRACT: A biocatalyst, prepared by the immobilization of a cryotolerant strain of Saccharomyces cerevisiae on gluten pellets, was freeze-dried without any protecting medium and used for repeated batch fermentations of wort for each of the temperatures 15, 10, 5, and 0 degrees C. The fermentation time for freeze-dried immobilized cells was about 2-fold that of the corresponding time for wet immobilized cells on gluten pellets, and lower than the corresponding time for freeze-dried free cells, especially at 5 and 0 degrees C. Beers produced by freeze-dried immobilized cells contained alcohol levels in the range of 5.0-5.5% v/v, diacetyl concentrations lower than 0.5 mg/L, polyphenol concentrations lower than 145.5 mg/L, and free cell concentrations lower than 3 g/L. As a result, they had a very good clarity after the end of primary fermentation. The amounts of amyl alcohols were lower than 129.1 mg/L and reduced as the temperature was decreased. Ethyl acetate concentrations were found in the range of 22.1-29.2 mg/L, giving a very good aroma and taste in the produced beers.
    No preview · Article · Feb 2001 · Journal of Agricultural and Food Chemistry
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    M Iconomopoulou · M Kanellaki · K Psarianos · AA Koutinas
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    ABSTRACT: Freeze-dried delignified cellulosic (DC) material supported biocatalyst is proposed as a suitable form of biocatalyst to be preserved. The alcoholic fermentation of glucose using freeze-dried immobilized cells is reported. Freeze-dried immobilized baker's yeast cells on DC material do not need any protective medium during freeze-drying. The effect of initial glucose concentration and temperature on the alcoholic fermentation kinetic parameters is reported in the present study. It was found that the freeze-dried immobilized cells ferment more quickly than free freeze-dried cells and have a lower fermentation rate as compared with wet immobilized cells. However, repeated batch fermentations showed freeze-dried immobilized cells to ferment at about the same fermentation rate as wet immobilized cells. The results indicate that the freeze-dried immobilized cells must be further studied to establish a process for the preservation of immobilized cells.
    Preview · Article · Apr 2000 · Journal of Agricultural and Food Chemistry
  • V. Bakoyianis · M. Kanellaki · K. Psarianos · A.A. Koutinas
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    ABSTRACT: A comparison study concerning the formation of methanol, ethylacetate, propanol‐1, isobutanol and amyl alcohols (mixture of 2‐ methylbutanol‐1 and 3‐methylbutanol‐1) in continuous wine‐making by γ‐alumina, kissiris and alginates supported biocatalysts is performed in this investigation. The effect of temperature was also examined. Methanol content was not affected by the support, process and temperature, but the concentrations of the other above compounds were reduced by the reduction of the temperature in all studied supports. The percentage content of ethyl acetate in the total volatile determined plus methanol was higher in the case of immobilized cells than in free cells. Kissiris supported biocatalyst increased this parameter but the other and free cells decreased it. Propanol‐1, isobutyl‐alcohol and amyl alcohols as percentage on total volatiles determined plus methanol were less than those of free cells for all supports and temperatures studied. The effect of the improvement of the formation of volatiles on quality of the wine was examined by a taste test.
    No preview · Article · Nov 1998 · Food Biotechnology
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    ABSTRACT: Four alcohol resistant strains isolated from a Greek vineyard plantation were examined for low temperature wine making. The strains found to be of Saccharomyces cerevisiae species. These yeasts were adapted by gradually establishing feeding and temperature conditions during yeast production. After adaptation these yeasts fermented must and prepared wines at relatively low temperatures in the range −2 to 5°C. More specifically at −2°C the strains Visanto-1 and AXAZ-1 produced wines of 9·9 and 10% v/v alcohol at 150 and 155 days, respectively.
    No preview · Article · Sep 1996 · Process Biochemistry