Study On Selection And Fermentation Conditions Of Trehalose-producing Strain

Trehalose is a nonreducing disaccharide with two glucose residues. Because trehalosehas nonspecific property protection, it achieves widespread application in variety of fieldsincluding pharmaceutics, foods, and biochemistry, etc. Yeast is a major strain of trehaloseproduction. The main research contents are as follows: the selection of yeast, the measuringmethod for trehalose, the optimization of medium and culture conditions, and the purificationof the intracellular trehalose.The measurement methods of trehalose were studied. It includes the confirmation of thelength of boiling time, the confirmation of the length of spectrum of measurement and thestandard curve of trehalose. The results shown the optimal boiling time was eight minutes.The optimal length of spectrum was620nm, the formula of calculating trehalose in yeast weregot from the standard curve of trehalose.Alcohol yeast was selected by the study of several different kinds of yeasts. The culturemedium and operation conditions of alcohol yeast were optimized. The optimized processingparameters were sucrose concentration3.76%, amount of yeast extract1.44%, sodiumchloride concentration1.88%. The yield of trehalose in this culture was0.7385g/L. The bestoperation conditions for trehalose fermentation system were70mL of liquid volume,7%ofyeast inoculums, pH5.0,30°C of temperature. The yield of trehalose in this operationconditions was up to0.9940g/L.The extraction technology of trehalose from alcohol yeast was studied. Taking distilledwater as extractant, the experimental results show that the best reaction conditions are:reaction temperature,70°C; ratio of dry yeast weight to distilled water volum,1∶20;extraction time,1h.Process of purification, refining and crystallization were also studied. Active carbon wasa kind of effective sorbent, which was used in decolorization of trehalose extracting liquid.The optimum decoloring condition of trehalose extracting solution were that active carbonamount was0.5%(g/ml), the temperature of decolorization was60°C, pH was5, and the time of decolorization was20min.732cation exchange resin and717anion exchange resin wereused for removing motley ions and pigments further, and the volume ratio of732cationexchange resin to717anion exchange resin is2∶1. The desalination and decolorization rateswere up to99.43%and61.4%, respectively. Then extraction solution containing trehaloseafter refining was condensed to mass proporation between40%and50%. When ethanol offour times as much as extraction solution volum was added, crystal of trehalose was obtained.