| In this paper, molasses alcohol waste water controlling approaches and the characters of various good alcohol yeast strain including their breeding selectively methods were surveyed at first. Then on the basis of finding out the limit value of the single factor to the alcohol fermentation after analysis and determination of main inorganic and organic matter in molasses and its alcohol ic waste water , construct i on of yeast cells to self-flocculate by protop last fusion was put forward in this paper. Then the yeast strain suitable for molasses alcoholic waste water recycling was breed after physical and chemical mutagenization adopted to several times. And design a new operation process of the thin stillage recycling fermentation pretreated with O3/H2O2 combined with fusants and adding sugar method. The main research contents and results of the thesis are reported as following:(1) According to different quantities were added to molasses al coholic waste water through imitating the metallic ions and organic acids content in alcoholic waste water, find out the limit value of the single factor and point out each influence factor to the alcohol fermentation and its reaction mechanism of biochemistry effect. That provides reference for taming yeast strain , the control of the harmful ingredients and thin still age recycling ratio. Under the laboratory term, the limit value of K+, Na+, Ca2+ , Mg2+ , Fe2+ , Cu2+ , Zn2+, Al3+ Pb2+ As3+ to the alcohol fermentation respectively is 850, 1300, 800, 500, 600~700, 11~13, 1200, 600, 21, 3mg/L K+ is the most great factor to the alcohol fermentation, Ca2+,Mg2+ ,Cu2+ are in the next place of influence factors. The Iimit value of oxalic acid, lactic acid, citric acid, acetic acid, fumaric acid to the alcohol fermentation respectively is 0. 9%, 3. 5%,0. 9%,0. 3%,1. 4%. Lactic acid and acetic acid are considered as the key influential factor in organic acids. Therefore it is necessary to reduce organic acids contain or to improvethe ability of yeast strain suitable for high density organic acids through taming yeast strain in order to realize high thin stillage recycling ratio.(2) Genetic markers of Schizosaccharomyces pombe and Saccharomyces cerevisiae have been establ ished. Fusant has been obtained by protoplast fusionand by going down to 15 generations. At last , the fusant XDST has good genetic stable fermentation capacity and can self-flocculate strongly.(3) The fusant XDST achieves higher density salt and organic acids tolerance compared with original alcohol yeast yeast 01 after physical and chemical mutagenization adopted to several times. Then the objective yeast strain more suitable for molasses alcoholic waste water recycling was breed on the basis of fusant XDST through continuous taming technique. The ratio of thin stillage recycling fermentation of the objective yeast strain is improved from 30% to 50-60%(adopting the double concentration flow). The berns value is 2.2. Theobjective yeast strain can flocculate well by itself at the end of fermentation. That will be helpful for the strain to be used as a cell immobilization method in industrial production.(4) A new operation of three times adding sugar method was put forward instead of traditional double concentration flow technique making use of the trait of the objective yeast strain more suitable for molasses alcoholic waste water recycling. From the whole fermentation flow (ferment 72 hours), the process is thick mash fermentation and realized the target of the ratio 80% of thin stillage recycling fermentation. The optimum fermentation conditions and technique were gained through the orthogonal experiments: initial pH 5.0, 37 C fermentation , the ratio of thin stillage recycling fermentation 80%, adding sugar in batch with the initial sugar concentration M=20 mL That is the most similar to industrial production.(5) Making use of O3/H2O2process of advanced oxidation processes desalt, decolour and reduce COD of molasses alcohol ic waste water , which makes prepared for thin stillage recycling severa... |
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