Study On Screen Of Yeast Strain With High Trehalose Yields,Optimization Of Culture Medium,Extraction And Purification

Trehalose is a nonreducing disaccharide of glucose.It has an excellent ability to protect biological cells(such as protein,nucleic acid,etc)from damage caused by drying and dehydration,so it has been the studing focus for scientists in the recent years.In this paper taking AnQi active fresh yeast after rejuvenation as starting strains,mutation was obtained by UV, chemical reagents and microwave heating on the base of making sure the measuring method and observation of fermentation culture.During UV mutation process,there were three turns of UV-mutation on the starting strains in all and the mutation time was 40-60 seconds.After one turn of mutation , strains with high mutation ratio were selected from fifteen strains to receive the next turn for mutation.In the three turns of mutation a high yielding trehalose strain was screened and its trehalose yeilds was 19.52g /100g dry yeast.During chemical mutation two chemical reagents with low toxicity were used together and the best proportion of the two reagents were described as follow: 5-Bu was 300 μ mol/L and Pingyangmycin hydrochloride was 5 μ mol/L. Of the chemical mutation the highest yielding of strain was 15.98g / 100g dry yeast.Through microwave mutation the highest yielding of strain was 17.01g / 100g dry yeast.At the same time the operation conditions and cultrue medium of the yeast strain were also optimized.The best operation conditions for trehalose fermentation system was described as follows: the best ration speed was 240r/min and temperature was 35℃.On this base,the carbon source concentration nitrogen source concentration , proportion of carbon and nitrogen source concentration, constitute and content of inorganic salt and microelement also were investigated to find the best culture medium in which the yeast strain synthesize trehalose furthest.Technology of extraction trehalose from active dry yeast was studied.Taking distilled water as extraction solvent,the maximum extraction ratio of trehalose from active yeast that was 16.32gtrehalose / 100g dry yesat was obtained when the extraction temperature was 80℃, ratio of dry yeast weight and distilled water volum was 1:20 and the extraction time was one hour and pH had no effect on extraction ratio of trehalose.By comparing the effects of different extraction solvent on the extraction ratio of trehalose, high yield of trehalose ,21.54g trehaolse /100g dry yeast, could be obtained when 1 % GaO solution as extraction solvent.To study the technology of extraction trehalose from waste beer yeast,the material was dealed with in a peculiar way in which waste yeast was heated in oven for a period of time then made into powder and compared traditional extraction method with Suoshi extractionmethod.The experimental results in this paper showed that the extraction ratio of trehalose by Suoshi method was almost three times as much as by traditional method.The extraction technology was described as follow: ratio of waste yeast weight and distilled water volum was 3:50,temperature was 80℃, degree of vacuum was 0.09Mpa, the time of extraction was one hour and the yield of trehalose was 6.505gtrehalose / kg dry waste yeast,however the all content of trehalose in waste beer yeast was 7.98g trehalose/kg dry waste yeast.Purification , refining and crystallization of prosess were also studied.Alkali metals were used to remove protein, active carbon was used to remove pigments and ion exchange resin to remove motley ions and pigments further. 001×7 cation exchange resin and 201×7 anion exchange resin composed the mixed ion exchange column and the volume proportion of 201×7 anion exchange resin and 001×7 cation exchange resin was 2:1.When extraction solvent containing trehalose after refining was condensed to almost mass proporation 15 % and crystalled in ethanol of four times as much as extraction solvent volum for one week ,crystal of trehalose with prismatic shape could be obtained and the crystal ratio was 80%.