The Pressure Affecting On Yeast And Producing Trehalose

Under the condition of high pressure, the irritative reaction occurred after being stimulated for the Yeast cells. Trehalose is one of the important irritative metabolic productions of plenty of microorganism , during they were intimidated by the environment, it is a nonreducing disaccharide with two glucose residues. Because trehalose exhibit protective action against damage of high molecular substances, it achieve widespread application in a variety of fields including foods , pharmaceutics and biochemistry etc. In this paper, the main research contents include establishing the optimum conditions of Yeast thalli accumulating trehalose in the high pressure circumstance, intracellular trehalose accumulated by different sorts of Yeasts varying from the precessing time and corresponding trehalose synthase system activity, the change of some parameter of different Yeast cells under other conditions.At first, by using Bakers Yeast (saccharomyces cerevisiae) as initial strain, the factors affecting the intracecellular trehalose production were studied in this paper, containing different pressure value, processing time, reaction temperature, pH value, pressing and decompressing rates, culture time before processing, culture medium and many factors. The optimum conditions of Yeast thalli accumulating trehalose in the high pressure circumstance was established , as they are, pressure value0.5~1.0MPa, processing time 3h, reaction temperature 34 C, pH6.0, pressing and depressing rates0.05~0.10MPa/min, selecting composite culture medium.Secondly, three sorts of Saccharomyces cerevisiae, six strains(Beer yeast GZH and USA, Baker yeast Saf and WR-5, Alcohol yeast AY-3 and AY-11) wre selected as our study objects under the condition of 1.0MPa. Thalli accumulating intracecellular trehalose varying from processing time wre studied. The results showed different sorts of yeasts had various sensitiveity for the high pressure, and further explained the synthesis path of intracecellular trehalose had possibly many kinds, as if the same sort had also probably more than one paths. Simultaneously the new method of determining trehalose synthase system activity was established. Yeast cells wre penetrated by 2% toluene and 0.2% EDTA solution as infiltration reagent, 1.0% glucose solution was used enzyme catalysis substrates. Corresponding trehalose synthase system activity was determined byusing biosensor instrument-sulfate anthrone colorimetric.Finally the cell electron micrograph were taken by using scan electron microscope. The results showed Yeast cells distortion after high pressure processing, There were many shrinkage, drapes, pleats and dents on the cell surfaces, presented spindle shape. Simultaneously concomitant characters were the active cell quantity and survival rate deceasing, biomass reducing and pH appreciably rising etc. All of them had a relation with the intracecellular trehalose content. In addition, CO2 and N2 wre used as pressing gas and Baker's Yeast WR-5 was selected research strain, the cell penetrability was denoted by the conductance value variety of the solution. The factors affecting the cell penetrability including different pressure value, pressing and decompressing rates, processing time, reaction temperature wre studied in this paper.